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<?php

/**
 * Base Class for all \phpseclib\Crypt\* cipher classes
 *
 * PHP version 5
 *
 * Internally for phpseclib developers:
 *  If you plan to add a new cipher class, please note following rules:
 *
 *  - The new \phpseclib\Crypt\* cipher class should extend \phpseclib\Crypt\Base
 *
 *  - Following methods are then required to be overridden/overloaded:
 *
 *    - _encryptBlock()
 *
 *    - _decryptBlock()
 *
 *    - _setupKey()
 *
 *  - All other methods are optional to be overridden/overloaded
 *
 *  - Look at the source code of the current ciphers how they extend \phpseclib\Crypt\Base
 *    and take one of them as a start up for the new cipher class.
 *
 *  - Please read all the other comments/notes/hints here also for each class var/method
 *
 * @category  Crypt
 * @package   Base
 * @author    Jim Wigginton <terrafrost@php.net>
 * @author    Hans-Juergen Petrich <petrich@tronic-media.com>
 * @copyright 2007 Jim Wigginton
 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
 * @link      http://phpseclib.sourceforge.net
 */

namespace phpseclib\Crypt;

/**
 * Base Class for all \phpseclib\Crypt\* cipher classes
 *
 * @package Base
 * @author  Jim Wigginton <terrafrost@php.net>
 * @author  Hans-Juergen Petrich <petrich@tronic-media.com>
 */
abstract class Base
{
    /**#@+
     * @access public
     * @see \phpseclib\Crypt\Base::encrypt()
     * @see \phpseclib\Crypt\Base::decrypt()
     */
    /**
     * Encrypt / decrypt using the Counter mode.
     *
     * Set to -1 since that's what Crypt/Random.php uses to index the CTR mode.
     *
     * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Counter_.28CTR.29
     */
    const MODE_CTR = -1;
    /**
     * Encrypt / decrypt using the Electronic Code Book mode.
     *
     * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Electronic_codebook_.28ECB.29
     */
    const MODE_ECB = 1;
    /**
     * Encrypt / decrypt using the Code Book Chaining mode.
     *
     * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Cipher-block_chaining_.28CBC.29
     */
    const MODE_CBC = 2;
    /**
     * Encrypt / decrypt using the Cipher Feedback mode.
     *
     * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Cipher_feedback_.28CFB.29
     */
    const MODE_CFB = 3;
    /**
     * Encrypt / decrypt using the Cipher Feedback mode (8bit)
     */
    const MODE_CFB8 = 6;
    /**
     * Encrypt / decrypt using the Output Feedback mode (8bit)
     */
    const MODE_OFB8 = 7;
    /**
     * Encrypt / decrypt using the Output Feedback mode.
     *
     * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Output_feedback_.28OFB.29
     */
    const MODE_OFB = 4;
    /**
     * Encrypt / decrypt using streaming mode.
     */
    const MODE_STREAM = 5;
    /**#@-*/

    /**
     * Whirlpool available flag
     *
     * @see \phpseclib\Crypt\Base::_hashInlineCryptFunction()
     * @var bool
     * @access private
     */
    static $WHIRLPOOL_AVAILABLE;

    /**#@+
     * @access private
     * @see \phpseclib\Crypt\Base::__construct()
     */
    /**
     * Base value for the internal implementation $engine switch
     */
    const ENGINE_INTERNAL = 1;
    /**
     * Base value for the mcrypt implementation $engine switch
     */
    const ENGINE_MCRYPT = 2;
    /**
     * Base value for the mcrypt implementation $engine switch
     */
    const ENGINE_OPENSSL = 3;
    /**#@-*/

    /**
     * The Encryption Mode
     *
     * @see self::__construct()
     * @var int
     * @access private
     */
    var $mode;

    /**
     * The Block Length of the block cipher
     *
     * @var int
     * @access private
     */
    var $block_size = 16;

    /**
     * The Key
     *
     * @see self::setKey()
     * @var string
     * @access private
     */
    var $key = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";

    /**
     * The Initialization Vector
     *
     * @see self::setIV()
     * @var string
     * @access private
     */
    var $iv = '';

    /**
     * A "sliding" Initialization Vector
     *
     * @see self::enableContinuousBuffer()
     * @see self::_clearBuffers()
     * @var string
     * @access private
     */
    var $encryptIV;

    /**
     * A "sliding" Initialization Vector
     *
     * @see self::enableContinuousBuffer()
     * @see self::_clearBuffers()
     * @var string
     * @access private
     */
    var $decryptIV;

    /**
     * Continuous Buffer status
     *
     * @see self::enableContinuousBuffer()
     * @var bool
     * @access private
     */
    var $continuousBuffer = false;

    /**
     * Encryption buffer for CTR, OFB and CFB modes
     *
     * @see self::encrypt()
     * @see self::_clearBuffers()
     * @var array
     * @access private
     */
    var $enbuffer;

    /**
     * Decryption buffer for CTR, OFB and CFB modes
     *
     * @see self::decrypt()
     * @see self::_clearBuffers()
     * @var array
     * @access private
     */
    var $debuffer;

    /**
     * mcrypt resource for encryption
     *
     * The mcrypt resource can be recreated every time something needs to be created or it can be created just once.
     * Since mcrypt operates in continuous mode, by default, it'll need to be recreated when in non-continuous mode.
     *
     * @see self::encrypt()
     * @var resource
     * @access private
     */
    var $enmcrypt;

    /**
     * mcrypt resource for decryption
     *
     * The mcrypt resource can be recreated every time something needs to be created or it can be created just once.
     * Since mcrypt operates in continuous mode, by default, it'll need to be recreated when in non-continuous mode.
     *
     * @see self::decrypt()
     * @var resource
     * @access private
     */
    var $demcrypt;

    /**
     * Does the enmcrypt resource need to be (re)initialized?
     *
     * @see \phpseclib\Crypt\Twofish::setKey()
     * @see \phpseclib\Crypt\Twofish::setIV()
     * @var bool
     * @access private
     */
    var $enchanged = true;

    /**
     * Does the demcrypt resource need to be (re)initialized?
     *
     * @see \phpseclib\Crypt\Twofish::setKey()
     * @see \phpseclib\Crypt\Twofish::setIV()
     * @var bool
     * @access private
     */
    var $dechanged = true;

    /**
     * mcrypt resource for CFB mode
     *
     * mcrypt's CFB mode, in (and only in) buffered context,
     * is broken, so phpseclib implements the CFB mode by it self,
     * even when the mcrypt php extension is available.
     *
     * In order to do the CFB-mode work (fast) phpseclib
     * use a separate ECB-mode mcrypt resource.
     *
     * @link http://phpseclib.sourceforge.net/cfb-demo.phps
     * @see self::encrypt()
     * @see self::decrypt()
     * @see self::_setupMcrypt()
     * @var resource
     * @access private
     */
    var $ecb;

    /**
     * Optimizing value while CFB-encrypting
     *
     * Only relevant if $continuousBuffer enabled
     * and $engine == self::ENGINE_MCRYPT
     *
     * It's faster to re-init $enmcrypt if
     * $buffer bytes > $cfb_init_len than
     * using the $ecb resource furthermore.
     *
     * This value depends of the chosen cipher
     * and the time it would be needed for it's
     * initialization [by mcrypt_generic_init()]
     * which, typically, depends on the complexity
     * on its internaly Key-expanding algorithm.
     *
     * @see self::encrypt()
     * @var int
     * @access private
     */
    var $cfb_init_len = 600;

    /**
     * Does internal cipher state need to be (re)initialized?
     *
     * @see self::setKey()
     * @see self::setIV()
     * @see self::disableContinuousBuffer()
     * @var bool
     * @access private
     */
    var $changed = true;

    /**
     * Padding status
     *
     * @see self::enablePadding()
     * @var bool
     * @access private
     */
    var $padding = true;

    /**
     * Is the mode one that is paddable?
     *
     * @see self::__construct()
     * @var bool
     * @access private
     */
    var $paddable = false;

    /**
     * Holds which crypt engine internaly should be use,
     * which will be determined automatically on __construct()
     *
     * Currently available $engines are:
     * - self::ENGINE_OPENSSL  (very fast, php-extension: openssl, extension_loaded('openssl') required)
     * - self::ENGINE_MCRYPT   (fast, php-extension: mcrypt, extension_loaded('mcrypt') required)
     * - self::ENGINE_INTERNAL (slower, pure php-engine, no php-extension required)
     *
     * @see self::_setEngine()
     * @see self::encrypt()
     * @see self::decrypt()
     * @var int
     * @access private
     */
    var $engine;

    /**
     * Holds the preferred crypt engine
     *
     * @see self::_setEngine()
     * @see self::setPreferredEngine()
     * @var int
     * @access private
     */
    var $preferredEngine;

    /**
     * The mcrypt specific name of the cipher
     *
     * Only used if $engine == self::ENGINE_MCRYPT
     *
     * @link http://www.php.net/mcrypt_module_open
     * @link http://www.php.net/mcrypt_list_algorithms
     * @see self::_setupMcrypt()
     * @var string
     * @access private
     */
    var $cipher_name_mcrypt;

    /**
     * The openssl specific name of the cipher
     *
     * Only used if $engine == self::ENGINE_OPENSSL
     *
     * @link http://www.php.net/openssl-get-cipher-methods
     * @var string
     * @access private
     */
    var $cipher_name_openssl;

    /**
     * The openssl specific name of the cipher in ECB mode
     *
     * If OpenSSL does not support the mode we're trying to use (CTR)
     * it can still be emulated with ECB mode.
     *
     * @link http://www.php.net/openssl-get-cipher-methods
     * @var string
     * @access private
     */
    var $cipher_name_openssl_ecb;

    /**
     * The default salt used by setPassword()
     *
     * @see self::setPassword()
     * @var string
     * @access private
     */
    var $password_default_salt = 'phpseclib/salt';

    /**
     * The name of the performance-optimized callback function
     *
     * Used by encrypt() / decrypt()
     * only if $engine == self::ENGINE_INTERNAL
     *
     * @see self::encrypt()
     * @see self::decrypt()
     * @see self::_setupInlineCrypt()
     * @see self::$use_inline_crypt
     * @var Callback
     * @access private
     */
    var $inline_crypt;

    /**
     * Holds whether performance-optimized $inline_crypt() can/should be used.
     *
     * @see self::encrypt()
     * @see self::decrypt()
     * @see self::inline_crypt
     * @var mixed
     * @access private
     */
    var $use_inline_crypt = true;

    /**
     * If OpenSSL can be used in ECB but not in CTR we can emulate CTR
     *
     * @see self::_openssl_ctr_process()
     * @var bool
     * @access private
     */
    var $openssl_emulate_ctr = false;

    /**
     * Determines what options are passed to openssl_encrypt/decrypt
     *
     * @see self::isValidEngine()
     * @var mixed
     * @access private
     */
    var $openssl_options;

    /**
     * Has the key length explicitly been set or should it be derived from the key, itself?
     *
     * @see self::setKeyLength()
     * @var bool
     * @access private
     */
    var $explicit_key_length = false;

    /**
     * Don't truncate / null pad key
     *
     * @see self::_clearBuffers()
     * @var bool
     * @access private
     */
    var $skip_key_adjustment = false;

    /**
     * Default Constructor.
     *
     * Determines whether or not the mcrypt extension should be used.
     *
     * $mode could be:
     *
     * - self::MODE_ECB
     *
     * - self::MODE_CBC
     *
     * - self::MODE_CTR
     *
     * - self::MODE_CFB
     *
     * - self::MODE_OFB
     *
     * If not explicitly set, self::MODE_CBC will be used.
     *
     * @param int $mode
     * @access public
     */
    function __construct($mode = self::MODE_CBC)
    {
        // $mode dependent settings
        switch ($mode) {
            case self::MODE_ECB:
                $this->paddable = true;
                $this->mode = self::MODE_ECB;
                break;
            case self::MODE_CTR:
            case self::MODE_CFB:
            case self::MODE_CFB8:
            case self::MODE_OFB8:
            case self::MODE_OFB:
            case self::MODE_STREAM:
                $this->mode = $mode;
                break;
            case self::MODE_CBC:
            default:
                $this->paddable = true;
                $this->mode = self::MODE_CBC;
        }

        $this->_setEngine();

        // Determining whether inline crypting can be used by the cipher
        if ($this->use_inline_crypt !== false) {
            $this->use_inline_crypt = version_compare(PHP_VERSION, '5.3.0') >= 0 || function_exists('create_function');
        }

        if (!defined('PHP_INT_SIZE')) {
            define('PHP_INT_SIZE', 4);
        }

        if (!defined('CRYPT_BASE_USE_REG_INTVAL')) {
            switch (true) {
                // PHP_OS & "\xDF\xDF\xDF" == strtoupper(substr(PHP_OS, 0, 3)), but a lot faster
                case (PHP_OS & "\xDF\xDF\xDF") === 'WIN':
                case !function_exists('php_uname'):
                case !is_string(php_uname('m')):
                case (php_uname('m') & "\xDF\xDF\xDF") != 'ARM':
                case PHP_INT_SIZE == 8:
                    define('CRYPT_BASE_USE_REG_INTVAL', true);
                    break;
                case (php_uname('m') & "\xDF\xDF\xDF") == 'ARM':
                    switch (true) {
                        /* PHP 7.0.0 introduced a bug that affected 32-bit ARM processors:

                           https://github.com/php/php-src/commit/716da71446ebbd40fa6cf2cea8a4b70f504cc3cd

                           altho the changelogs make no mention of it, this bug was fixed with this commit:

                           https://github.com/php/php-src/commit/c1729272b17a1fe893d1a54e423d3b71470f3ee8

                           affected versions of PHP are: 7.0.x, 7.1.0 - 7.1.23 and 7.2.0 - 7.2.11 */
                        case PHP_VERSION_ID >= 70000 && PHP_VERSION_ID <= 70123:
                        case PHP_VERSION_ID >= 70200 && PHP_VERSION_ID <= 70211:
                            define('CRYPT_BASE_USE_REG_INTVAL', false);
                            break;
                        default:
                            define('CRYPT_BASE_USE_REG_INTVAL', true);
                    }
            }
        }
    }

    /**
     * Sets the initialization vector. (optional)
     *
     * SetIV is not required when self::MODE_ECB (or ie for AES: \phpseclib\Crypt\AES::MODE_ECB) is being used.  If not explicitly set, it'll be assumed
     * to be all zero's.
     *
     * @access public
     * @param string $iv
     * @internal Can be overwritten by a sub class, but does not have to be
     */
    function setIV($iv)
    {
        if ($this->mode == self::MODE_ECB) {
            return;
        }

        $this->iv = $iv;
        $this->changed = true;
    }

    /**
     * Sets the key length.
     *
     * Keys with explicitly set lengths need to be treated accordingly
     *
     * @access public
     * @param int $length
     */
    function setKeyLength($length)
    {
        $this->explicit_key_length = true;
        $this->changed = true;
        $this->_setEngine();
    }

    /**
     * Returns the current key length in bits
     *
     * @access public
     * @return int
     */
    function getKeyLength()
    {
        return $this->key_length << 3;
    }

    /**
     * Returns the current block length in bits
     *
     * @access public
     * @return int
     */
    function getBlockLength()
    {
        return $this->block_size << 3;
    }

    /**
     * Sets the key.
     *
     * The min/max length(s) of the key depends on the cipher which is used.
     * If the key not fits the length(s) of the cipher it will paded with null bytes
     * up to the closest valid key length.  If the key is more than max length,
     * we trim the excess bits.
     *
     * If the key is not explicitly set, it'll be assumed to be all null bytes.
     *
     * @access public
     * @param string $key
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function setKey($key)
    {
        if (!$this->explicit_key_length) {
            $this->setKeyLength(strlen($key) << 3);
            $this->explicit_key_length = false;
        }

        $this->key = $key;
        $this->changed = true;
        $this->_setEngine();
    }

    /**
     * Sets the password.
     *
     * Depending on what $method is set to, setPassword()'s (optional) parameters are as follows:
     *     {@link http://en.wikipedia.org/wiki/PBKDF2 pbkdf2} or pbkdf1:
     *         $hash, $salt, $count, $dkLen
     *
     *         Where $hash (default = sha1) currently supports the following hashes: see: Crypt/Hash.php
     *     {@link https://en.wikipedia.org/wiki/Bcrypt bcypt}:
     *         $salt, $rounds, $keylen
     *
     *         This is a modified version of bcrypt used by OpenSSH.
     *
     * @see Crypt/Hash.php
     * @param string $password
     * @param string $method
     * @return bool
     * @access public
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function setPassword($password, $method = 'pbkdf2')
    {
        $key = '';

        switch ($method) {
            case 'bcrypt':
                $func_args = func_get_args();

                if (!isset($func_args[2])) {
                    return false;
                }

                $salt = $func_args[2];

                $rounds = isset($func_args[3]) ? $func_args[3] : 16;
                $keylen = isset($func_args[4]) ? $func_args[4] : $this->key_length;

                $bf = new Blowfish();
                $key = $bf->bcrypt_pbkdf($password, $salt, $keylen + $this->block_size, $rounds);
                if (!$key) {
                    return false;
                }

                $this->setKey(substr($key, 0, $keylen));
                $this->setIV(substr($key, $keylen));

                return true;
            default: // 'pbkdf2' or 'pbkdf1'
                $func_args = func_get_args();

                // Hash function
                $hash = isset($func_args[2]) ? $func_args[2] : 'sha1';

                // WPA and WPA2 use the SSID as the salt
                $salt = isset($func_args[3]) ? $func_args[3] : $this->password_default_salt;

                // RFC2898#section-4.2 uses 1,000 iterations by default
                // WPA and WPA2 use 4,096.
                $count = isset($func_args[4]) ? $func_args[4] : 1000;

                // Keylength
                if (isset($func_args[5])) {
                    $dkLen = $func_args[5];
                } else {
                    $dkLen = $method == 'pbkdf1' ? 2 * $this->key_length : $this->key_length;
                }

                switch (true) {
                    case $method == 'pbkdf1':
                        $hashObj = new Hash();
                        $hashObj->setHash($hash);
                        if ($dkLen > $hashObj->getLength()) {
                            user_error('Derived key too long');
                            return false;
                        }
                        $t = $password . $salt;
                        for ($i = 0; $i < $count; ++$i) {
                            $t = $hashObj->hash($t);
                        }
                        $key = substr($t, 0, $dkLen);

                        $this->setKey(substr($key, 0, $dkLen >> 1));
                        $this->setIV(substr($key, $dkLen >> 1));

                        return true;
                    // Determining if php[>=5.5.0]'s hash_pbkdf2() function avail- and useable
                    case !function_exists('hash_pbkdf2'):
                    case !function_exists('hash_algos'):
                    case !in_array($hash, hash_algos()):
                        $i = 1;
                        $hmac = new Hash();
                        $hmac->setHash($hash);
                        $hmac->setKey($password);
                        while (strlen($key) < $dkLen) {
                            $f = $u = $hmac->hash($salt . pack('N', $i++));
                            for ($j = 2; $j <= $count; ++$j) {
                                $u = $hmac->hash($u);
                                $f^= $u;
                            }
                            $key.= $f;
                        }
                        $key = substr($key, 0, $dkLen);
                        break;
                    default:
                        $key = hash_pbkdf2($hash, $password, $salt, $count, $dkLen, true);
                }
        }

        $this->setKey($key);

        return true;
    }

    /**
     * Encrypts a message.
     *
     * $plaintext will be padded with additional bytes such that it's length is a multiple of the block size. Other cipher
     * implementations may or may not pad in the same manner.  Other common approaches to padding and the reasons why it's
     * necessary are discussed in the following
     * URL:
     *
     * {@link http://www.di-mgt.com.au/cryptopad.html http://www.di-mgt.com.au/cryptopad.html}
     *
     * An alternative to padding is to, separately, send the length of the file.  This is what SSH, in fact, does.
     * strlen($plaintext) will still need to be a multiple of the block size, however, arbitrary values can be added to make it that
     * length.
     *
     * @see self::decrypt()
     * @access public
     * @param string $plaintext
     * @return string $ciphertext
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function encrypt($plaintext)
    {
        if ($this->paddable) {
            $plaintext = $this->_pad($plaintext);
        }

        if ($this->engine === self::ENGINE_OPENSSL) {
            if ($this->changed) {
                $this->_clearBuffers();
                $this->changed = false;
            }
            switch ($this->mode) {
                case self::MODE_STREAM:
                    return openssl_encrypt($plaintext, $this->cipher_name_openssl, $this->key, $this->openssl_options);
                case self::MODE_ECB:
                    $result = @openssl_encrypt($plaintext, $this->cipher_name_openssl, $this->key, $this->openssl_options);
                    return !defined('OPENSSL_RAW_DATA') ? substr($result, 0, -$this->block_size) : $result;
                case self::MODE_CBC:
                    $result = openssl_encrypt($plaintext, $this->cipher_name_openssl, $this->key, $this->openssl_options, $this->encryptIV);
                    if (!defined('OPENSSL_RAW_DATA')) {
                        $result = substr($result, 0, -$this->block_size);
                    }
                    if ($this->continuousBuffer) {
                        $this->encryptIV = substr($result, -$this->block_size);
                    }
                    return $result;
                case self::MODE_CTR:
                    return $this->_openssl_ctr_process($plaintext, $this->encryptIV, $this->enbuffer);
                case self::MODE_CFB:
                    // cfb loosely routines inspired by openssl's:
                    // {@link http://cvs.openssl.org/fileview?f=openssl/crypto/modes/cfb128.c&v=1.3.2.2.2.1}
                    $ciphertext = '';
                    if ($this->continuousBuffer) {
                        $iv = &$this->encryptIV;
                        $pos = &$this->enbuffer['pos'];
                    } else {
                        $iv = $this->encryptIV;
                        $pos = 0;
                    }
                    $len = strlen($plaintext);
                    $i = 0;
                    if ($pos) {
                        $orig_pos = $pos;
                        $max = $this->block_size - $pos;
                        if ($len >= $max) {
                            $i = $max;
                            $len-= $max;
                            $pos = 0;
                        } else {
                            $i = $len;
                            $pos+= $len;
                            $len = 0;
                        }
                        // ie. $i = min($max, $len), $len-= $i, $pos+= $i, $pos%= $blocksize
                        $ciphertext = substr($iv, $orig_pos) ^ $plaintext;
                        $iv = substr_replace($iv, $ciphertext, $orig_pos, $i);
                        $plaintext = substr($plaintext, $i);
                    }

                    $overflow = $len % $this->block_size;

                    if ($overflow) {
                        $ciphertext.= openssl_encrypt(substr($plaintext, 0, -$overflow) . str_repeat("\0", $this->block_size), $this->cipher_name_openssl, $this->key, $this->openssl_options, $iv);
                        $iv = $this->_string_pop($ciphertext, $this->block_size);

                        $size = $len - $overflow;
                        $block = $iv ^ substr($plaintext, -$overflow);
                        $iv = substr_replace($iv, $block, 0, $overflow);
                        $ciphertext.= $block;
                        $pos = $overflow;
                    } elseif ($len) {
                        $ciphertext = openssl_encrypt($plaintext, $this->cipher_name_openssl, $this->key, $this->openssl_options, $iv);
                        $iv = substr($ciphertext, -$this->block_size);
                    }

                    return $ciphertext;
                case self::MODE_CFB8:
                    $ciphertext = openssl_encrypt($plaintext, $this->cipher_name_openssl, $this->key, $this->openssl_options, $this->encryptIV);
                    if ($this->continuousBuffer) {
                        if (($len = strlen($ciphertext)) >= $this->block_size) {
                            $this->encryptIV = substr($ciphertext, -$this->block_size);
                        } else {
                            $this->encryptIV = substr($this->encryptIV, $len - $this->block_size) . substr($ciphertext, -$len);
                        }
                    }
                    return $ciphertext;
                case self::MODE_OFB8:
                    // OpenSSL has built in support for cfb8 but not ofb8
                    $ciphertext = '';
                    $len = strlen($plaintext);
                    $iv = $this->encryptIV;

                    for ($i = 0; $i < $len; ++$i) {
                        $xor = openssl_encrypt($iv, $this->cipher_name_openssl_ecb, $this->key, $this->openssl_options, $this->decryptIV);
                        $ciphertext.= $plaintext[$i] ^ $xor;
                        $iv = substr($iv, 1) . $xor[0];
                    }

                    if ($this->continuousBuffer) {
                        $this->encryptIV = $iv;
                    }
                    break;
                case self::MODE_OFB:
                    return $this->_openssl_ofb_process($plaintext, $this->encryptIV, $this->enbuffer);
            }
        }

        if ($this->engine === self::ENGINE_MCRYPT) {
            set_error_handler(array($this, 'do_nothing'));

            if ($this->changed) {
                $this->_setupMcrypt();
                $this->changed = false;
            }
            if ($this->enchanged) {
                mcrypt_generic_init($this->enmcrypt, $this->key, $this->encryptIV);
                $this->enchanged = false;
            }

            // re: {@link http://phpseclib.sourceforge.net/cfb-demo.phps}
            // using mcrypt's default handing of CFB the above would output two different things.  using phpseclib's
            // rewritten CFB implementation the above outputs the same thing twice.
            if ($this->mode == self::MODE_CFB && $this->continuousBuffer) {
                $block_size = $this->block_size;
                $iv = &$this->encryptIV;
                $pos = &$this->enbuffer['pos'];
                $len = strlen($plaintext);
                $ciphertext = '';
                $i = 0;
                if ($pos) {
                    $orig_pos = $pos;
                    $max = $block_size - $pos;
                    if ($len >= $max) {
                        $i = $max;
                        $len-= $max;
                        $pos = 0;
                    } else {
                        $i = $len;
                        $pos+= $len;
                        $len = 0;
                    }
                    $ciphertext = substr($iv, $orig_pos) ^ $plaintext;
                    $iv = substr_replace($iv, $ciphertext, $orig_pos, $i);
                    $this->enbuffer['enmcrypt_init'] = true;
                }
                if ($len >= $block_size) {
                    if ($this->enbuffer['enmcrypt_init'] === false || $len > $this->cfb_init_len) {
                        if ($this->enbuffer['enmcrypt_init'] === true) {
                            mcrypt_generic_init($this->enmcrypt, $this->key, $iv);
                            $this->enbuffer['enmcrypt_init'] = false;
                        }
                        $ciphertext.= mcrypt_generic($this->enmcrypt, substr($plaintext, $i, $len - $len % $block_size));
                        $iv = substr($ciphertext, -$block_size);
                        $len%= $block_size;
                    } else {
                        while ($len >= $block_size) {
                            $iv = mcrypt_generic($this->ecb, $iv) ^ substr($plaintext, $i, $block_size);
                            $ciphertext.= $iv;
                            $len-= $block_size;
                            $i+= $block_size;
                        }
                    }
                }

                if ($len) {
                    $iv = mcrypt_generic($this->ecb, $iv);
                    $block = $iv ^ substr($plaintext, -$len);
                    $iv = substr_replace($iv, $block, 0, $len);
                    $ciphertext.= $block;
                    $pos = $len;
                }

                restore_error_handler();

                return $ciphertext;
            }

            $ciphertext = mcrypt_generic($this->enmcrypt, $plaintext);

            if (!$this->continuousBuffer) {
                mcrypt_generic_init($this->enmcrypt, $this->key, $this->encryptIV);
            }

            restore_error_handler();

            return $ciphertext;
        }

        if ($this->changed) {
            $this->_setup();
            $this->changed = false;
        }
        if ($this->use_inline_crypt) {
            $inline = $this->inline_crypt;
            return $inline('encrypt', $this, $plaintext);
        }

        $buffer = &$this->enbuffer;
        $block_size = $this->block_size;
        $ciphertext = '';
        switch ($this->mode) {
            case self::MODE_ECB:
                for ($i = 0; $i < strlen($plaintext); $i+=$block_size) {
                    $ciphertext.= $this->_encryptBlock(substr($plaintext, $i, $block_size));
                }
                break;
            case self::MODE_CBC:
                $xor = $this->encryptIV;
                for ($i = 0; $i < strlen($plaintext); $i+=$block_size) {
                    $block = substr($plaintext, $i, $block_size);
                    $block = $this->_encryptBlock($block ^ $xor);
                    $xor = $block;
                    $ciphertext.= $block;
                }
                if ($this->continuousBuffer) {
                    $this->encryptIV = $xor;
                }
                break;
            case self::MODE_CTR:
                $xor = $this->encryptIV;
                if (strlen($buffer['ciphertext'])) {
                    for ($i = 0; $i < strlen($plaintext); $i+=$block_size) {
                        $block = substr($plaintext, $i, $block_size);
                        if (strlen($block) > strlen($buffer['ciphertext'])) {
                            $buffer['ciphertext'].= $this->_encryptBlock($xor);
                            $this->_increment_str($xor);
                        }
                        $key = $this->_string_shift($buffer['ciphertext'], $block_size);
                        $ciphertext.= $block ^ $key;
                    }
                } else {
                    for ($i = 0; $i < strlen($plaintext); $i+=$block_size) {
                        $block = substr($plaintext, $i, $block_size);
                        $key = $this->_encryptBlock($xor);
                        $this->_increment_str($xor);
                        $ciphertext.= $block ^ $key;
                    }
                }
                if ($this->continuousBuffer) {
                    $this->encryptIV = $xor;
                    if ($start = strlen($plaintext) % $block_size) {
                        $buffer['ciphertext'] = substr($key, $start) . $buffer['ciphertext'];
                    }
                }
                break;
            case self::MODE_CFB:
                // cfb loosely routines inspired by openssl's:
                // {@link http://cvs.openssl.org/fileview?f=openssl/crypto/modes/cfb128.c&v=1.3.2.2.2.1}
                if ($this->continuousBuffer) {
                    $iv = &$this->encryptIV;
                    $pos = &$buffer['pos'];
                } else {
                    $iv = $this->encryptIV;
                    $pos = 0;
                }
                $len = strlen($plaintext);
                $i = 0;
                if ($pos) {
                    $orig_pos = $pos;
                    $max = $block_size - $pos;
                    if ($len >= $max) {
                        $i = $max;
                        $len-= $max;
                        $pos = 0;
                    } else {
                        $i = $len;
                        $pos+= $len;
                        $len = 0;
                    }
                    // ie. $i = min($max, $len), $len-= $i, $pos+= $i, $pos%= $blocksize
                    $ciphertext = substr($iv, $orig_pos) ^ $plaintext;
                    $iv = substr_replace($iv, $ciphertext, $orig_pos, $i);
                }
                while ($len >= $block_size) {
                    $iv = $this->_encryptBlock($iv) ^ substr($plaintext, $i, $block_size);
                    $ciphertext.= $iv;
                    $len-= $block_size;
                    $i+= $block_size;
                }
                if ($len) {
                    $iv = $this->_encryptBlock($iv);
                    $block = $iv ^ substr($plaintext, $i);
                    $iv = substr_replace($iv, $block, 0, $len);
                    $ciphertext.= $block;
                    $pos = $len;
                }
                break;
            case self::MODE_CFB8:
                // compared to regular CFB, which encrypts a block at a time,
                // here, we're encrypting a byte at a time
                $ciphertext = '';
                $len = strlen($plaintext);
                $iv = $this->encryptIV;

                for ($i = 0; $i < $len; ++$i) {
                    $ciphertext.= ($c = $plaintext[$i] ^ $this->_encryptBlock($iv));
                    $iv = substr($iv, 1) . $c;
                }

                if ($this->continuousBuffer) {
                    if ($len >= $block_size) {
                        $this->encryptIV = substr($ciphertext, -$block_size);
                    } else {
                        $this->encryptIV = substr($this->encryptIV, $len - $block_size) . substr($ciphertext, -$len);
                    }
                }
                break;
            case self::MODE_OFB8:
                $ciphertext = '';
                $len = strlen($plaintext);
                $iv = $this->encryptIV;

                for ($i = 0; $i < $len; ++$i) {
                    $xor = $this->_encryptBlock($iv);
                    $ciphertext.= $plaintext[$i] ^ $xor;
                    $iv = substr($iv, 1) . $xor[0];
                }

                if ($this->continuousBuffer) {
                    $this->encryptIV = $iv;
                }
                break;
            case self::MODE_OFB:
                $xor = $this->encryptIV;
                if (strlen($buffer['xor'])) {
                    for ($i = 0; $i < strlen($plaintext); $i+=$block_size) {
                        $block = substr($plaintext, $i, $block_size);
                        if (strlen($block) > strlen($buffer['xor'])) {
                            $xor = $this->_encryptBlock($xor);
                            $buffer['xor'].= $xor;
                        }
                        $key = $this->_string_shift($buffer['xor'], $block_size);
                        $ciphertext.= $block ^ $key;
                    }
                } else {
                    for ($i = 0; $i < strlen($plaintext); $i+=$block_size) {
                        $xor = $this->_encryptBlock($xor);
                        $ciphertext.= substr($plaintext, $i, $block_size) ^ $xor;
                    }
                    $key = $xor;
                }
                if ($this->continuousBuffer) {
                    $this->encryptIV = $xor;
                    if ($start = strlen($plaintext) % $block_size) {
                        $buffer['xor'] = substr($key, $start) . $buffer['xor'];
                    }
                }
                break;
            case self::MODE_STREAM:
                $ciphertext = $this->_encryptBlock($plaintext);
                break;
        }

        return $ciphertext;
    }

    /**
     * Decrypts a message.
     *
     * If strlen($ciphertext) is not a multiple of the block size, null bytes will be added to the end of the string until
     * it is.
     *
     * @see self::encrypt()
     * @access public
     * @param string $ciphertext
     * @return string $plaintext
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function decrypt($ciphertext)
    {
        if ($this->paddable) {
            // we pad with chr(0) since that's what mcrypt_generic does.  to quote from {@link http://www.php.net/function.mcrypt-generic}:
            // "The data is padded with "\0" to make sure the length of the data is n * blocksize."
            $ciphertext = str_pad($ciphertext, strlen($ciphertext) + ($this->block_size - strlen($ciphertext) % $this->block_size) % $this->block_size, chr(0));
        }

        if ($this->engine === self::ENGINE_OPENSSL) {
            if ($this->changed) {
                $this->_clearBuffers();
                $this->changed = false;
            }
            switch ($this->mode) {
                case self::MODE_STREAM:
                    $plaintext = openssl_decrypt($ciphertext, $this->cipher_name_openssl, $this->key, $this->openssl_options);
                    break;
                case self::MODE_ECB:
                    if (!defined('OPENSSL_RAW_DATA')) {
                        $ciphertext.= @openssl_encrypt('', $this->cipher_name_openssl_ecb, $this->key, true);
                    }
                    $plaintext = openssl_decrypt($ciphertext, $this->cipher_name_openssl, $this->key, $this->openssl_options);
                    break;
                case self::MODE_CBC:
                    if (!defined('OPENSSL_RAW_DATA')) {
                        $padding = str_repeat(chr($this->block_size), $this->block_size) ^ substr($ciphertext, -$this->block_size);
                        $ciphertext.= substr(@openssl_encrypt($padding, $this->cipher_name_openssl_ecb, $this->key, true), 0, $this->block_size);
                        $offset = 2 * $this->block_size;
                    } else {
                        $offset = $this->block_size;
                    }
                    $plaintext = openssl_decrypt($ciphertext, $this->cipher_name_openssl, $this->key, $this->openssl_options, $this->decryptIV);
                    if ($this->continuousBuffer) {
                        $this->decryptIV = substr($ciphertext, -$offset, $this->block_size);
                    }
                    break;
                case self::MODE_CTR:
                    $plaintext = $this->_openssl_ctr_process($ciphertext, $this->decryptIV, $this->debuffer);
                    break;
                case self::MODE_CFB:
                    // cfb loosely routines inspired by openssl's:
                    // {@link http://cvs.openssl.org/fileview?f=openssl/crypto/modes/cfb128.c&v=1.3.2.2.2.1}
                    $plaintext = '';
                    if ($this->continuousBuffer) {
                        $iv = &$this->decryptIV;
                        $pos = &$this->debuffer['pos'];
                    } else {
                        $iv = $this->decryptIV;
                        $pos = 0;
                    }
                    $len = strlen($ciphertext);
                    $i = 0;
                    if ($pos) {
                        $orig_pos = $pos;
                        $max = $this->block_size - $pos;
                        if ($len >= $max) {
                            $i = $max;
                            $len-= $max;
                            $pos = 0;
                        } else {
                            $i = $len;
                            $pos+= $len;
                            $len = 0;
                        }
                        // ie. $i = min($max, $len), $len-= $i, $pos+= $i, $pos%= $this->blocksize
                        $plaintext = substr($iv, $orig_pos) ^ $ciphertext;
                        $iv = substr_replace($iv, substr($ciphertext, 0, $i), $orig_pos, $i);
                        $ciphertext = substr($ciphertext, $i);
                    }
                    $overflow = $len % $this->block_size;
                    if ($overflow) {
                        $plaintext.= openssl_decrypt(substr($ciphertext, 0, -$overflow), $this->cipher_name_openssl, $this->key, $this->openssl_options, $iv);
                        if ($len - $overflow) {
                            $iv = substr($ciphertext, -$overflow - $this->block_size, -$overflow);
                        }
                        $iv = openssl_encrypt(str_repeat("\0", $this->block_size), $this->cipher_name_openssl, $this->key, $this->openssl_options, $iv);
                        $plaintext.= $iv ^ substr($ciphertext, -$overflow);
                        $iv = substr_replace($iv, substr($ciphertext, -$overflow), 0, $overflow);
                        $pos = $overflow;
                    } elseif ($len) {
                        $plaintext.= openssl_decrypt($ciphertext, $this->cipher_name_openssl, $this->key, $this->openssl_options, $iv);
                        $iv = substr($ciphertext, -$this->block_size);
                    }
                    break;
                case self::MODE_CFB8:
                    $plaintext = openssl_decrypt($ciphertext, $this->cipher_name_openssl, $this->key, $this->openssl_options, $this->decryptIV);
                    if ($this->continuousBuffer) {
                        if (($len = strlen($ciphertext)) >= $this->block_size) {
                            $this->decryptIV = substr($ciphertext, -$this->block_size);
                        } else {
                            $this->decryptIV = substr($this->decryptIV, $len - $this->block_size) . substr($ciphertext, -$len);
                        }
                    }
                    break;
                case self::MODE_OFB8:
                    $plaintext = '';
                    $len = strlen($ciphertext);
                    $iv = $this->decryptIV;

                    for ($i = 0; $i < $len; ++$i) {
                        $xor = openssl_encrypt($iv, $this->cipher_name_openssl_ecb, $this->key, $this->openssl_options, $this->decryptIV);
                        $plaintext.= $ciphertext[$i] ^ $xor;
                        $iv = substr($iv, 1) . $xor[0];
                    }

                    if ($this->continuousBuffer) {
                        $this->decryptIV = $iv;
                    }
                    break;
                case self::MODE_OFB:
                    $plaintext = $this->_openssl_ofb_process($ciphertext, $this->decryptIV, $this->debuffer);
            }

            return $this->paddable ? $this->_unpad($plaintext) : $plaintext;
        }

        if ($this->engine === self::ENGINE_MCRYPT) {
            set_error_handler(array($this, 'do_nothing'));
            $block_size = $this->block_size;
            if ($this->changed) {
                $this->_setupMcrypt();
                $this->changed = false;
            }
            if ($this->dechanged) {
                mcrypt_generic_init($this->demcrypt, $this->key, $this->decryptIV);
                $this->dechanged = false;
            }

            if ($this->mode == self::MODE_CFB && $this->continuousBuffer) {
                $iv = &$this->decryptIV;
                $pos = &$this->debuffer['pos'];
                $len = strlen($ciphertext);
                $plaintext = '';
                $i = 0;
                if ($pos) {
                    $orig_pos = $pos;
                    $max = $block_size - $pos;
                    if ($len >= $max) {
                        $i = $max;
                        $len-= $max;
                        $pos = 0;
                    } else {
                        $i = $len;
                        $pos+= $len;
                        $len = 0;
                    }
                    // ie. $i = min($max, $len), $len-= $i, $pos+= $i, $pos%= $blocksize
                    $plaintext = substr($iv, $orig_pos) ^ $ciphertext;
                    $iv = substr_replace($iv, substr($ciphertext, 0, $i), $orig_pos, $i);
                }
                if ($len >= $block_size) {
                    $cb = substr($ciphertext, $i, $len - $len % $block_size);
                    $plaintext.= mcrypt_generic($this->ecb, $iv . $cb) ^ $cb;
                    $iv = substr($cb, -$block_size);
                    $len%= $block_size;
                }
                if ($len) {
                    $iv = mcrypt_generic($this->ecb, $iv);
                    $plaintext.= $iv ^ substr($ciphertext, -$len);
                    $iv = substr_replace($iv, substr($ciphertext, -$len), 0, $len);
                    $pos = $len;
                }

                restore_error_handler();

                return $plaintext;
            }

            $plaintext = mdecrypt_generic($this->demcrypt, $ciphertext);

            if (!$this->continuousBuffer) {
                mcrypt_generic_init($this->demcrypt, $this->key, $this->decryptIV);
            }

            restore_error_handler();

            return $this->paddable ? $this->_unpad($plaintext) : $plaintext;
        }

        if ($this->changed) {
            $this->_setup();
            $this->changed = false;
        }
        if ($this->use_inline_crypt) {
            $inline = $this->inline_crypt;
            return $inline('decrypt', $this, $ciphertext);
        }

        $block_size = $this->block_size;

        $buffer = &$this->debuffer;
        $plaintext = '';
        switch ($this->mode) {
            case self::MODE_ECB:
                for ($i = 0; $i < strlen($ciphertext); $i+=$block_size) {
                    $plaintext.= $this->_decryptBlock(substr($ciphertext, $i, $block_size));
                }
                break;
            case self::MODE_CBC:
                $xor = $this->decryptIV;
                for ($i = 0; $i < strlen($ciphertext); $i+=$block_size) {
                    $block = substr($ciphertext, $i, $block_size);
                    $plaintext.= $this->_decryptBlock($block) ^ $xor;
                    $xor = $block;
                }
                if ($this->continuousBuffer) {
                    $this->decryptIV = $xor;
                }
                break;
            case self::MODE_CTR:
                $xor = $this->decryptIV;
                if (strlen($buffer['ciphertext'])) {
                    for ($i = 0; $i < strlen($ciphertext); $i+=$block_size) {
                        $block = substr($ciphertext, $i, $block_size);
                        if (strlen($block) > strlen($buffer['ciphertext'])) {
                            $buffer['ciphertext'].= $this->_encryptBlock($xor);
                            $this->_increment_str($xor);
                        }
                        $key = $this->_string_shift($buffer['ciphertext'], $block_size);
                        $plaintext.= $block ^ $key;
                    }
                } else {
                    for ($i = 0; $i < strlen($ciphertext); $i+=$block_size) {
                        $block = substr($ciphertext, $i, $block_size);
                        $key = $this->_encryptBlock($xor);
                        $this->_increment_str($xor);
                        $plaintext.= $block ^ $key;
                    }
                }
                if ($this->continuousBuffer) {
                    $this->decryptIV = $xor;
                    if ($start = strlen($ciphertext) % $block_size) {
                        $buffer['ciphertext'] = substr($key, $start) . $buffer['ciphertext'];
                    }
                }
                break;
            case self::MODE_CFB:
                if ($this->continuousBuffer) {
                    $iv = &$this->decryptIV;
                    $pos = &$buffer['pos'];
                } else {
                    $iv = $this->decryptIV;
                    $pos = 0;
                }
                $len = strlen($ciphertext);
                $i = 0;
                if ($pos) {
                    $orig_pos = $pos;
                    $max = $block_size - $pos;
                    if ($len >= $max) {
                        $i = $max;
                        $len-= $max;
                        $pos = 0;
                    } else {
                        $i = $len;
                        $pos+= $len;
                        $len = 0;
                    }
                    // ie. $i = min($max, $len), $len-= $i, $pos+= $i, $pos%= $blocksize
                    $plaintext = substr($iv, $orig_pos) ^ $ciphertext;
                    $iv = substr_replace($iv, substr($ciphertext, 0, $i), $orig_pos, $i);
                }
                while ($len >= $block_size) {
                    $iv = $this->_encryptBlock($iv);
                    $cb = substr($ciphertext, $i, $block_size);
                    $plaintext.= $iv ^ $cb;
                    $iv = $cb;
                    $len-= $block_size;
                    $i+= $block_size;
                }
                if ($len) {
                    $iv = $this->_encryptBlock($iv);
                    $plaintext.= $iv ^ substr($ciphertext, $i);
                    $iv = substr_replace($iv, substr($ciphertext, $i), 0, $len);
                    $pos = $len;
                }
                break;
            case self::MODE_CFB8:
                $plaintext = '';
                $len = strlen($ciphertext);
                $iv = $this->decryptIV;

                for ($i = 0; $i < $len; ++$i) {
                    $plaintext.= $ciphertext[$i] ^ $this->_encryptBlock($iv);
                    $iv = substr($iv, 1) . $ciphertext[$i];
                }

                if ($this->continuousBuffer) {
                    if ($len >= $block_size) {
                        $this->decryptIV = substr($ciphertext, -$block_size);
                    } else {
                        $this->decryptIV = substr($this->decryptIV, $len - $block_size) . substr($ciphertext, -$len);
                    }
                }
                break;
            case self::MODE_OFB8:
                $plaintext = '';
                $len = strlen($ciphertext);
                $iv = $this->decryptIV;

                for ($i = 0; $i < $len; ++$i) {
                    $xor = $this->_encryptBlock($iv);
                    $plaintext.= $ciphertext[$i] ^ $xor;
                    $iv = substr($iv, 1) . $xor[0];
                }

                if ($this->continuousBuffer) {
                    $this->decryptIV = $iv;
                }
                break;
            case self::MODE_OFB:
                $xor = $this->decryptIV;
                if (strlen($buffer['xor'])) {
                    for ($i = 0; $i < strlen($ciphertext); $i+=$block_size) {
                        $block = substr($ciphertext, $i, $block_size);
                        if (strlen($block) > strlen($buffer['xor'])) {
                            $xor = $this->_encryptBlock($xor);
                            $buffer['xor'].= $xor;
                        }
                        $key = $this->_string_shift($buffer['xor'], $block_size);
                        $plaintext.= $block ^ $key;
                    }
                } else {
                    for ($i = 0; $i < strlen($ciphertext); $i+=$block_size) {
                        $xor = $this->_encryptBlock($xor);
                        $plaintext.= substr($ciphertext, $i, $block_size) ^ $xor;
                    }
                    $key = $xor;
                }
                if ($this->continuousBuffer) {
                    $this->decryptIV = $xor;
                    if ($start = strlen($ciphertext) % $block_size) {
                        $buffer['xor'] = substr($key, $start) . $buffer['xor'];
                    }
                }
                break;
            case self::MODE_STREAM:
                $plaintext = $this->_decryptBlock($ciphertext);
                break;
        }
        return $this->paddable ? $this->_unpad($plaintext) : $plaintext;
    }

    /**
     * OpenSSL CTR Processor
     *
     * PHP's OpenSSL bindings do not operate in continuous mode so we'll wrap around it. Since the keystream
     * for CTR is the same for both encrypting and decrypting this function is re-used by both Base::encrypt()
     * and Base::decrypt(). Also, OpenSSL doesn't implement CTR for all of it's symmetric ciphers so this
     * function will emulate CTR with ECB when necessary.
     *
     * @see self::encrypt()
     * @see self::decrypt()
     * @param string $plaintext
     * @param string $encryptIV
     * @param array $buffer
     * @return string
     * @access private
     */
    function _openssl_ctr_process($plaintext, &$encryptIV, &$buffer)
    {
        $ciphertext = '';

        $block_size = $this->block_size;
        $key = $this->key;

        if ($this->openssl_emulate_ctr) {
            $xor = $encryptIV;
            if (strlen($buffer['ciphertext'])) {
                for ($i = 0; $i < strlen($plaintext); $i+=$block_size) {
                    $block = substr($plaintext, $i, $block_size);
                    if (strlen($block) > strlen($buffer['ciphertext'])) {
                        $result = @openssl_encrypt($xor, $this->cipher_name_openssl_ecb, $key, $this->openssl_options);
                        $result = !defined('OPENSSL_RAW_DATA') ? substr($result, 0, -$this->block_size) : $result;
                        $buffer['ciphertext'].= $result;
                    }
                    $this->_increment_str($xor);
                    $otp = $this->_string_shift($buffer['ciphertext'], $block_size);
                    $ciphertext.= $block ^ $otp;
                }
            } else {
                for ($i = 0; $i < strlen($plaintext); $i+=$block_size) {
                    $block = substr($plaintext, $i, $block_size);
                    $otp = @openssl_encrypt($xor, $this->cipher_name_openssl_ecb, $key, $this->openssl_options);
                    $otp = !defined('OPENSSL_RAW_DATA') ? substr($otp, 0, -$this->block_size) : $otp;
                    $this->_increment_str($xor);
                    $ciphertext.= $block ^ $otp;
                }
            }
            if ($this->continuousBuffer) {
                $encryptIV = $xor;
                if ($start = strlen($plaintext) % $block_size) {
                    $buffer['ciphertext'] = substr($key, $start) . $buffer['ciphertext'];
                }
            }

            return $ciphertext;
        }

        if (strlen($buffer['ciphertext'])) {
            $ciphertext = $plaintext ^ $this->_string_shift($buffer['ciphertext'], strlen($plaintext));
            $plaintext = substr($plaintext, strlen($ciphertext));

            if (!strlen($plaintext)) {
                return $ciphertext;
            }
        }

        $overflow = strlen($plaintext) % $block_size;
        if ($overflow) {
            $plaintext2 = $this->_string_pop($plaintext, $overflow); // ie. trim $plaintext to a multiple of $block_size and put rest of $plaintext in $plaintext2
            $encrypted = openssl_encrypt($plaintext . str_repeat("\0", $block_size), $this->cipher_name_openssl, $key, $this->openssl_options, $encryptIV);
            $temp = $this->_string_pop($encrypted, $block_size);
            $ciphertext.= $encrypted . ($plaintext2 ^ $temp);
            if ($this->continuousBuffer) {
                $buffer['ciphertext'] = substr($temp, $overflow);
                $encryptIV = $temp;
            }
        } elseif (!strlen($buffer['ciphertext'])) {
            $ciphertext.= openssl_encrypt($plaintext . str_repeat("\0", $block_size), $this->cipher_name_openssl, $key, $this->openssl_options, $encryptIV);
            $temp = $this->_string_pop($ciphertext, $block_size);
            if ($this->continuousBuffer) {
                $encryptIV = $temp;
            }
        }
        if ($this->continuousBuffer) {
            if (!defined('OPENSSL_RAW_DATA')) {
                $encryptIV.= @openssl_encrypt('', $this->cipher_name_openssl_ecb, $key, $this->openssl_options);
            }
            $encryptIV = openssl_decrypt($encryptIV, $this->cipher_name_openssl_ecb, $key, $this->openssl_options);
            if ($overflow) {
                $this->_increment_str($encryptIV);
            }
        }

        return $ciphertext;
    }

    /**
     * OpenSSL OFB Processor
     *
     * PHP's OpenSSL bindings do not operate in continuous mode so we'll wrap around it. Since the keystream
     * for OFB is the same for both encrypting and decrypting this function is re-used by both Base::encrypt()
     * and Base::decrypt().
     *
     * @see self::encrypt()
     * @see self::decrypt()
     * @param string $plaintext
     * @param string $encryptIV
     * @param array $buffer
     * @return string
     * @access private
     */
    function _openssl_ofb_process($plaintext, &$encryptIV, &$buffer)
    {
        if (strlen($buffer['xor'])) {
            $ciphertext = $plaintext ^ $buffer['xor'];
            $buffer['xor'] = substr($buffer['xor'], strlen($ciphertext));
            $plaintext = substr($plaintext, strlen($ciphertext));
        } else {
            $ciphertext = '';
        }

        $block_size = $this->block_size;

        $len = strlen($plaintext);
        $key = $this->key;
        $overflow = $len % $block_size;

        if (strlen($plaintext)) {
            if ($overflow) {
                $ciphertext.= openssl_encrypt(substr($plaintext, 0, -$overflow) . str_repeat("\0", $block_size), $this->cipher_name_openssl, $key, $this->openssl_options, $encryptIV);
                $xor = $this->_string_pop($ciphertext, $block_size);
                if ($this->continuousBuffer) {
                    $encryptIV = $xor;
                }
                $ciphertext.= $this->_string_shift($xor, $overflow) ^ substr($plaintext, -$overflow);
                if ($this->continuousBuffer) {
                    $buffer['xor'] = $xor;
                }
            } else {
                $ciphertext = openssl_encrypt($plaintext, $this->cipher_name_openssl, $key, $this->openssl_options, $encryptIV);
                if ($this->continuousBuffer) {
                    $encryptIV = substr($ciphertext, -$block_size) ^ substr($plaintext, -$block_size);
                }
            }
        }

        return $ciphertext;
    }

    /**
     * phpseclib <-> OpenSSL Mode Mapper
     *
     * May need to be overwritten by classes extending this one in some cases
     *
     * @return int
     * @access private
     */
    function _openssl_translate_mode()
    {
        switch ($this->mode) {
            case self::MODE_ECB:
                return 'ecb';
            case self::MODE_CBC:
                return 'cbc';
            case self::MODE_CTR:
                return 'ctr';
            case self::MODE_CFB:
                return 'cfb';
            case self::MODE_CFB8:
                return 'cfb8';
            case self::MODE_OFB:
                return 'ofb';
        }
    }

    /**
     * Pad "packets".
     *
     * Block ciphers working by encrypting between their specified [$this->]block_size at a time
     * If you ever need to encrypt or decrypt something that isn't of the proper length, it becomes necessary to
     * pad the input so that it is of the proper length.
     *
     * Padding is enabled by default.  Sometimes, however, it is undesirable to pad strings.  Such is the case in SSH,
     * where "packets" are padded with random bytes before being encrypted.  Unpad these packets and you risk stripping
     * away characters that shouldn't be stripped away. (SSH knows how many bytes are added because the length is
     * transmitted separately)
     *
     * @see self::disablePadding()
     * @access public
     */
    function enablePadding()
    {
        $this->padding = true;
    }

    /**
     * Do not pad packets.
     *
     * @see self::enablePadding()
     * @access public
     */
    function disablePadding()
    {
        $this->padding = false;
    }

    /**
     * Treat consecutive "packets" as if they are a continuous buffer.
     *
     * Say you have a 32-byte plaintext $plaintext.  Using the default behavior, the two following code snippets
     * will yield different outputs:
     *
     * <code>
     *    echo $rijndael->encrypt(substr($plaintext,  0, 16));
     *    echo $rijndael->encrypt(substr($plaintext, 16, 16));
     * </code>
     * <code>
     *    echo $rijndael->encrypt($plaintext);
     * </code>
     *
     * The solution is to enable the continuous buffer.  Although this will resolve the above discrepancy, it creates
     * another, as demonstrated with the following:
     *
     * <code>
     *    $rijndael->encrypt(substr($plaintext, 0, 16));
     *    echo $rijndael->decrypt($rijndael->encrypt(substr($plaintext, 16, 16)));
     * </code>
     * <code>
     *    echo $rijndael->decrypt($rijndael->encrypt(substr($plaintext, 16, 16)));
     * </code>
     *
     * With the continuous buffer disabled, these would yield the same output.  With it enabled, they yield different
     * outputs.  The reason is due to the fact that the initialization vector's change after every encryption /
     * decryption round when the continuous buffer is enabled.  When it's disabled, they remain constant.
     *
     * Put another way, when the continuous buffer is enabled, the state of the \phpseclib\Crypt\*() object changes after each
     * encryption / decryption round, whereas otherwise, it'd remain constant.  For this reason, it's recommended that
     * continuous buffers not be used.  They do offer better security and are, in fact, sometimes required (SSH uses them),
     * however, they are also less intuitive and more likely to cause you problems.
     *
     * @see self::disableContinuousBuffer()
     * @access public
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function enableContinuousBuffer()
    {
        if ($this->mode == self::MODE_ECB) {
            return;
        }

        $this->continuousBuffer = true;

        $this->_setEngine();
    }

    /**
     * Treat consecutive packets as if they are a discontinuous buffer.
     *
     * The default behavior.
     *
     * @see self::enableContinuousBuffer()
     * @access public
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function disableContinuousBuffer()
    {
        if ($this->mode == self::MODE_ECB) {
            return;
        }
        if (!$this->continuousBuffer) {
            return;
        }

        $this->continuousBuffer = false;
        $this->changed = true;

        $this->_setEngine();
    }

    /**
     * Test for engine validity
     *
     * @see self::__construct()
     * @param int $engine
     * @access public
     * @return bool
     */
    function isValidEngine($engine)
    {
        switch ($engine) {
            case self::ENGINE_OPENSSL:
                if ($this->mode == self::MODE_STREAM && $this->continuousBuffer) {
                    return false;
                }
                $this->openssl_emulate_ctr = false;
                $result = $this->cipher_name_openssl &&
                          extension_loaded('openssl') &&
                          // PHP 5.3.0 - 5.3.2 did not let you set IV's
                          version_compare(PHP_VERSION, '5.3.3', '>=');
                if (!$result) {
                    return false;
                }

                // prior to PHP 5.4.0 OPENSSL_RAW_DATA and OPENSSL_ZERO_PADDING were not defined. instead of expecting an integer
                // $options openssl_encrypt expected a boolean $raw_data.
                if (!defined('OPENSSL_RAW_DATA')) {
                    $this->openssl_options = true;
                } else {
                    $this->openssl_options = OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING;
                }

                $methods = openssl_get_cipher_methods();
                if (in_array($this->cipher_name_openssl, $methods)) {
                    return true;
                }
                // not all of openssl's symmetric cipher's support ctr. for those
                // that don't we'll emulate it
                switch ($this->mode) {
                    case self::MODE_CTR:
                        if (in_array($this->cipher_name_openssl_ecb, $methods)) {
                            $this->openssl_emulate_ctr = true;
                            return true;
                        }
                }
                return false;
            case self::ENGINE_MCRYPT:
                set_error_handler(array($this, 'do_nothing'));
                $result = $this->cipher_name_mcrypt &&
                       extension_loaded('mcrypt') &&
                       in_array($this->cipher_name_mcrypt, mcrypt_list_algorithms());
                restore_error_handler();
                return $result;
            case self::ENGINE_INTERNAL:
                return true;
        }

        return false;
    }

    /**
     * Sets the preferred crypt engine
     *
     * Currently, $engine could be:
     *
     * - \phpseclib\Crypt\Base::ENGINE_OPENSSL  [very fast]
     *
     * - \phpseclib\Crypt\Base::ENGINE_MCRYPT   [fast]
     *
     * - \phpseclib\Crypt\Base::ENGINE_INTERNAL [slow]
     *
     * If the preferred crypt engine is not available the fastest available one will be used
     *
     * @see self::__construct()
     * @param int $engine
     * @access public
     */
    function setPreferredEngine($engine)
    {
        switch ($engine) {
            //case self::ENGINE_OPENSSL;
            case self::ENGINE_MCRYPT:
            case self::ENGINE_INTERNAL:
                $this->preferredEngine = $engine;
                break;
            default:
                $this->preferredEngine = self::ENGINE_OPENSSL;
        }

        $this->_setEngine();
    }

    /**
     * Returns the engine currently being utilized
     *
     * @see self::_setEngine()
     * @access public
     */
    function getEngine()
    {
        return $this->engine;
    }

    /**
     * Sets the engine as appropriate
     *
     * @see self::__construct()
     * @access private
     */
    function _setEngine()
    {
        $this->engine = null;

        $candidateEngines = array(
            $this->preferredEngine,
            self::ENGINE_OPENSSL,
            self::ENGINE_MCRYPT
        );
        foreach ($candidateEngines as $engine) {
            if ($this->isValidEngine($engine)) {
                $this->engine = $engine;
                break;
            }
        }
        if (!$this->engine) {
            $this->engine = self::ENGINE_INTERNAL;
        }

        if ($this->engine != self::ENGINE_MCRYPT && $this->enmcrypt) {
            set_error_handler(array($this, 'do_nothing'));
            // Closing the current mcrypt resource(s). _mcryptSetup() will, if needed,
            // (re)open them with the module named in $this->cipher_name_mcrypt
            mcrypt_module_close($this->enmcrypt);
            mcrypt_module_close($this->demcrypt);
            $this->enmcrypt = null;
            $this->demcrypt = null;

            if ($this->ecb) {
                mcrypt_module_close($this->ecb);
                $this->ecb = null;
            }
            restore_error_handler();
        }

        $this->changed = true;
    }

    /**
     * Encrypts a block
     *
     * Note: Must be extended by the child \phpseclib\Crypt\* class
     *
     * @access private
     * @param string $in
     * @return string
     */
    abstract function _encryptBlock($in);

    /**
     * Decrypts a block
     *
     * Note: Must be extended by the child \phpseclib\Crypt\* class
     *
     * @access private
     * @param string $in
     * @return string
     */
    abstract function _decryptBlock($in);

    /**
     * Setup the key (expansion)
     *
     * Only used if $engine == self::ENGINE_INTERNAL
     *
     * Note: Must extend by the child \phpseclib\Crypt\* class
     *
     * @see self::_setup()
     * @access private
     */
    abstract function _setupKey();

    /**
     * Setup the self::ENGINE_INTERNAL $engine
     *
     * (re)init, if necessary, the internal cipher $engine and flush all $buffers
     * Used (only) if $engine == self::ENGINE_INTERNAL
     *
     * _setup() will be called each time if $changed === true
     * typically this happens when using one or more of following public methods:
     *
     * - setKey()
     *
     * - setIV()
     *
     * - disableContinuousBuffer()
     *
     * - First run of encrypt() / decrypt() with no init-settings
     *
     * @see self::setKey()
     * @see self::setIV()
     * @see self::disableContinuousBuffer()
     * @access private
     * @internal _setup() is always called before en/decryption.
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function _setup()
    {
        $this->_clearBuffers();
        $this->_setupKey();

        if ($this->use_inline_crypt) {
            $this->_setupInlineCrypt();
        }
    }

    /**
     * Setup the self::ENGINE_MCRYPT $engine
     *
     * (re)init, if necessary, the (ext)mcrypt resources and flush all $buffers
     * Used (only) if $engine = self::ENGINE_MCRYPT
     *
     * _setupMcrypt() will be called each time if $changed === true
     * typically this happens when using one or more of following public methods:
     *
     * - setKey()
     *
     * - setIV()
     *
     * - disableContinuousBuffer()
     *
     * - First run of encrypt() / decrypt()
     *
     * @see self::setKey()
     * @see self::setIV()
     * @see self::disableContinuousBuffer()
     * @access private
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function _setupMcrypt()
    {
        $this->_clearBuffers();
        $this->enchanged = $this->dechanged = true;

        if (!isset($this->enmcrypt)) {
            static $mcrypt_modes = array(
                self::MODE_CTR    => 'ctr',
                self::MODE_ECB    => MCRYPT_MODE_ECB,
                self::MODE_CBC    => MCRYPT_MODE_CBC,
                self::MODE_CFB    => 'ncfb',
                self::MODE_CFB8   => MCRYPT_MODE_CFB,
                self::MODE_OFB    => MCRYPT_MODE_NOFB,
                self::MODE_OFB8   => MCRYPT_MODE_OFB,
                self::MODE_STREAM => MCRYPT_MODE_STREAM,
            );

            $this->demcrypt = mcrypt_module_open($this->cipher_name_mcrypt, '', $mcrypt_modes[$this->mode], '');
            $this->enmcrypt = mcrypt_module_open($this->cipher_name_mcrypt, '', $mcrypt_modes[$this->mode], '');

            // we need the $ecb mcrypt resource (only) in MODE_CFB with enableContinuousBuffer()
            // to workaround mcrypt's broken ncfb implementation in buffered mode
            // see: {@link http://phpseclib.sourceforge.net/cfb-demo.phps}
            if ($this->mode == self::MODE_CFB) {
                $this->ecb = mcrypt_module_open($this->cipher_name_mcrypt, '', MCRYPT_MODE_ECB, '');
            }
        } // else should mcrypt_generic_deinit be called?

        if ($this->mode == self::MODE_CFB) {
            mcrypt_generic_init($this->ecb, $this->key, str_repeat("\0", $this->block_size));
        }
    }

    /**
     * Pads a string
     *
     * Pads a string using the RSA PKCS padding standards so that its length is a multiple of the blocksize.
     * $this->block_size - (strlen($text) % $this->block_size) bytes are added, each of which is equal to
     * chr($this->block_size - (strlen($text) % $this->block_size)
     *
     * If padding is disabled and $text is not a multiple of the blocksize, the string will be padded regardless
     * and padding will, hence forth, be enabled.
     *
     * @see self::_unpad()
     * @param string $text
     * @access private
     * @return string
     */
    function _pad($text)
    {
        $length = strlen($text);

        if (!$this->padding) {
            if ($length % $this->block_size == 0) {
                return $text;
            } else {
                user_error("The plaintext's length ($length) is not a multiple of the block size ({$this->block_size})");
                $this->padding = true;
            }
        }

        $pad = $this->block_size - ($length % $this->block_size);

        return str_pad($text, $length + $pad, chr($pad));
    }

    /**
     * Unpads a string.
     *
     * If padding is enabled and the reported padding length is invalid the encryption key will be assumed to be wrong
     * and false will be returned.
     *
     * @see self::_pad()
     * @param string $text
     * @access private
     * @return string
     */
    function _unpad($text)
    {
        if (!$this->padding) {
            return $text;
        }

        $length = ord($text[strlen($text) - 1]);

        if (!$length || $length > $this->block_size) {
            return false;
        }

        return substr($text, 0, -$length);
    }

    /**
     * Clears internal buffers
     *
     * Clearing/resetting the internal buffers is done everytime
     * after disableContinuousBuffer() or on cipher $engine (re)init
     * ie after setKey() or setIV()
     *
     * @access public
     * @internal Could, but not must, extend by the child Crypt_* class
     */
    function _clearBuffers()
    {
        $this->enbuffer = $this->debuffer = array('ciphertext' => '', 'xor' => '', 'pos' => 0, 'enmcrypt_init' => true);

        // mcrypt's handling of invalid's $iv:
        // $this->encryptIV = $this->decryptIV = strlen($this->iv) == $this->block_size ? $this->iv : str_repeat("\0", $this->block_size);
        $this->encryptIV = $this->decryptIV = str_pad(substr($this->iv, 0, $this->block_size), $this->block_size, "\0");

        if (!$this->skip_key_adjustment) {
            $this->key = str_pad(substr($this->key, 0, $this->key_length), $this->key_length, "\0");
        }
    }

    /**
     * String Shift
     *
     * Inspired by array_shift
     *
     * @param string $string
     * @param int $index
     * @access private
     * @return string
     */
    function _string_shift(&$string, $index = 1)
    {
        $substr = substr($string, 0, $index);
        $string = substr($string, $index);
        return $substr;
    }

    /**
     * String Pop
     *
     * Inspired by array_pop
     *
     * @param string $string
     * @param int $index
     * @access private
     * @return string
     */
    function _string_pop(&$string, $index = 1)
    {
        $substr = substr($string, -$index);
        $string = substr($string, 0, -$index);
        return $substr;
    }

    /**
     * Increment the current string
     *
     * @see self::decrypt()
     * @see self::encrypt()
     * @param string $var
     * @access private
     */
    function _increment_str(&$var)
    {
        if (function_exists('sodium_increment')) {
            $var = strrev($var);
            sodium_increment($var);
            $var = strrev($var);
            return;
        }

        for ($i = 4; $i <= strlen($var); $i+= 4) {
            $temp = substr($var, -$i, 4);
            switch ($temp) {
                case "\xFF\xFF\xFF\xFF":
                    $var = substr_replace($var, "\x00\x00\x00\x00", -$i, 4);
                    break;
                case "\x7F\xFF\xFF\xFF":
                    $var = substr_replace($var, "\x80\x00\x00\x00", -$i, 4);
                    return;
                default:
                    $temp = unpack('Nnum', $temp);
                    $var = substr_replace($var, pack('N', $temp['num'] + 1), -$i, 4);
                    return;
            }
        }

        $remainder = strlen($var) % 4;

        if ($remainder == 0) {
            return;
        }

        $temp = unpack('Nnum', str_pad(substr($var, 0, $remainder), 4, "\0", STR_PAD_LEFT));
        $temp = substr(pack('N', $temp['num'] + 1), -$remainder);
        $var = substr_replace($var, $temp, 0, $remainder);
    }

    /**
     * Setup the performance-optimized function for de/encrypt()
     *
     * Stores the created (or existing) callback function-name
     * in $this->inline_crypt
     *
     * Internally for phpseclib developers:
     *
     *     _setupInlineCrypt() would be called only if:
     *
     *     - $engine == self::ENGINE_INTERNAL and
     *
     *     - $use_inline_crypt === true
     *
     *     - each time on _setup(), after(!) _setupKey()
     *
     *
     *     This ensures that _setupInlineCrypt() has always a
     *     full ready2go initializated internal cipher $engine state
     *     where, for example, the keys allready expanded,
     *     keys/block_size calculated and such.
     *
     *     It is, each time if called, the responsibility of _setupInlineCrypt():
     *
     *     - to set $this->inline_crypt to a valid and fully working callback function
     *       as a (faster) replacement for encrypt() / decrypt()
     *
     *     - NOT to create unlimited callback functions (for memory reasons!)
     *       no matter how often _setupInlineCrypt() would be called. At some
     *       point of amount they must be generic re-useable.
     *
     *     - the code of _setupInlineCrypt() it self,
     *       and the generated callback code,
     *       must be, in following order:
     *       - 100% safe
     *       - 100% compatible to encrypt()/decrypt()
     *       - using only php5+ features/lang-constructs/php-extensions if
     *         compatibility (down to php4) or fallback is provided
     *       - readable/maintainable/understandable/commented and... not-cryptic-styled-code :-)
     *       - >= 10% faster than encrypt()/decrypt() [which is, by the way,
     *         the reason for the existence of _setupInlineCrypt() :-)]
     *       - memory-nice
     *       - short (as good as possible)
     *
     * Note: - _setupInlineCrypt() is using _createInlineCryptFunction() to create the full callback function code.
     *       - In case of using inline crypting, _setupInlineCrypt() must extend by the child \phpseclib\Crypt\* class.
     *       - The following variable names are reserved:
     *         - $_*  (all variable names prefixed with an underscore)
     *         - $self (object reference to it self. Do not use $this, but $self instead)
     *         - $in (the content of $in has to en/decrypt by the generated code)
     *       - The callback function should not use the 'return' statement, but en/decrypt'ing the content of $in only
     *
     *
     * @see self::_setup()
     * @see self::_createInlineCryptFunction()
     * @see self::encrypt()
     * @see self::decrypt()
     * @access private
     * @internal If a Crypt_* class providing inline crypting it must extend _setupInlineCrypt()
     */
    function _setupInlineCrypt()
    {
        // If, for any reason, an extending \phpseclib\Crypt\Base() \phpseclib\Crypt\* class
        // not using inline crypting then it must be ensured that: $this->use_inline_crypt = false
        // ie in the class var declaration of $use_inline_crypt in general for the \phpseclib\Crypt\* class,
        // in the constructor at object instance-time
        // or, if it's runtime-specific, at runtime

        $this->use_inline_crypt = false;
    }

    /**
     * Creates the performance-optimized function for en/decrypt()
     *
     * Internally for phpseclib developers:
     *
     *    _createInlineCryptFunction():
     *
     *    - merge the $cipher_code [setup'ed by _setupInlineCrypt()]
     *      with the current [$this->]mode of operation code
     *
     *    - create the $inline function, which called by encrypt() / decrypt()
     *      as its replacement to speed up the en/decryption operations.
     *
     *    - return the name of the created $inline callback function
     *
     *    - used to speed up en/decryption
     *
     *
     *
     *    The main reason why can speed up things [up to 50%] this way are:
     *
     *    - using variables more effective then regular.
     *      (ie no use of expensive arrays but integers $k_0, $k_1 ...
     *      or even, for example, the pure $key[] values hardcoded)
     *
     *    - avoiding 1000's of function calls of ie _encryptBlock()
     *      but inlining the crypt operations.
     *      in the mode of operation for() loop.
     *
     *    - full loop unroll the (sometimes key-dependent) rounds
     *      avoiding this way ++$i counters and runtime-if's etc...
     *
     *    The basic code architectur of the generated $inline en/decrypt()
     *    lambda function, in pseudo php, is:
     *
     *    <code>
     *    +----------------------------------------------------------------------------------------------+
     *    | callback $inline = create_function:                                                          |
     *    | lambda_function_0001_crypt_ECB($action, $text)                                               |
     *    | {                                                                                            |
     *    |     INSERT PHP CODE OF:                                                                      |
     *    |     $cipher_code['init_crypt'];                  // general init code.                       |
     *    |                                                  // ie: $sbox'es declarations used for       |
     *    |                                                  //     encrypt and decrypt'ing.             |
     *    |                                                                                              |
     *    |     switch ($action) {                                                                       |
     *    |         case 'encrypt':                                                                      |
     *    |             INSERT PHP CODE OF:                                                              |
     *    |             $cipher_code['init_encrypt'];       // encrypt sepcific init code.               |
     *    |                                                    ie: specified $key or $box                |
     *    |                                                        declarations for encrypt'ing.         |
     *    |                                                                                              |
     *    |             foreach ($ciphertext) {                                                          |
     *    |                 $in = $block_size of $ciphertext;                                            |
     *    |                                                                                              |
     *    |                 INSERT PHP CODE OF:                                                          |
     *    |                 $cipher_code['encrypt_block'];  // encrypt's (string) $in, which is always:  |
     *    |                                                 // strlen($in) == $this->block_size          |
     *    |                                                 // here comes the cipher algorithm in action |
     *    |                                                 // for encryption.                           |
     *    |                                                 // $cipher_code['encrypt_block'] has to      |
     *    |                                                 // encrypt the content of the $in variable   |
     *    |                                                                                              |
     *    |                 $plaintext .= $in;                                                           |
     *    |             }                                                                                |
     *    |             return $plaintext;                                                               |
     *    |                                                                                              |
     *    |         case 'decrypt':                                                                      |
     *    |             INSERT PHP CODE OF:                                                              |
     *    |             $cipher_code['init_decrypt'];       // decrypt sepcific init code                |
     *    |                                                    ie: specified $key or $box                |
     *    |                                                        declarations for decrypt'ing.         |
     *    |             foreach ($plaintext) {                                                           |
     *    |                 $in = $block_size of $plaintext;                                             |
     *    |                                                                                              |
     *    |                 INSERT PHP CODE OF:                                                          |
     *    |                 $cipher_code['decrypt_block'];  // decrypt's (string) $in, which is always   |
     *    |                                                 // strlen($in) == $this->block_size          |
     *    |                                                 // here comes the cipher algorithm in action |
     *    |                                                 // for decryption.                           |
     *    |                                                 // $cipher_code['decrypt_block'] has to      |
     *    |                                                 // decrypt the content of the $in variable   |
     *    |                 $ciphertext .= $in;                                                          |
     *    |             }                                                                                |
     *    |             return $ciphertext;                                                              |
     *    |     }                                                                                        |
     *    | }                                                                                            |
     *    +----------------------------------------------------------------------------------------------+
     *    </code>
     *
     *    See also the \phpseclib\Crypt\*::_setupInlineCrypt()'s for
     *    productive inline $cipher_code's how they works.
     *
     *    Structure of:
     *    <code>
     *    $cipher_code = array(
     *        'init_crypt'    => (string) '', // optional
     *        'init_encrypt'  => (string) '', // optional
     *        'init_decrypt'  => (string) '', // optional
     *        'encrypt_block' => (string) '', // required
     *        'decrypt_block' => (string) ''  // required
     *    );
     *    </code>
     *
     * @see self::_setupInlineCrypt()
     * @see self::encrypt()
     * @see self::decrypt()
     * @param array $cipher_code
     * @access private
     * @return string (the name of the created callback function)
     */
    function _createInlineCryptFunction($cipher_code)
    {
        $block_size = $this->block_size;

        // optional
        $init_crypt    = isset($cipher_code['init_crypt'])    ? $cipher_code['init_crypt']    : '';
        $init_encrypt  = isset($cipher_code['init_encrypt'])  ? $cipher_code['init_encrypt']  : '';
        $init_decrypt  = isset($cipher_code['init_decrypt'])  ? $cipher_code['init_decrypt']  : '';
        // required
        $encrypt_block = $cipher_code['encrypt_block'];
        $decrypt_block = $cipher_code['decrypt_block'];

        // Generating mode of operation inline code,
        // merged with the $cipher_code algorithm
        // for encrypt- and decryption.
        switch ($this->mode) {
            case self::MODE_ECB:
                $encrypt = $init_encrypt . '
                    $_ciphertext = "";
                    $_plaintext_len = strlen($_text);

                    for ($_i = 0; $_i < $_plaintext_len; $_i+= '.$block_size.') {
                        $in = substr($_text, $_i, '.$block_size.');
                        '.$encrypt_block.'
                        $_ciphertext.= $in;
                    }

                    return $_ciphertext;
                    ';

                $decrypt = $init_decrypt . '
                    $_plaintext = "";
                    $_text = str_pad($_text, strlen($_text) + ('.$block_size.' - strlen($_text) % '.$block_size.') % '.$block_size.', chr(0));
                    $_ciphertext_len = strlen($_text);

                    for ($_i = 0; $_i < $_ciphertext_len; $_i+= '.$block_size.') {
                        $in = substr($_text, $_i, '.$block_size.');
                        '.$decrypt_block.'
                        $_plaintext.= $in;
                    }

                    return $self->_unpad($_plaintext);
                    ';
                break;
            case self::MODE_CTR:
                $encrypt = $init_encrypt . '
                    $_ciphertext = "";
                    $_plaintext_len = strlen($_text);
                    $_xor = $self->encryptIV;
                    $_buffer = &$self->enbuffer;
                    if (strlen($_buffer["ciphertext"])) {
                        for ($_i = 0; $_i < $_plaintext_len; $_i+= '.$block_size.') {
                            $_block = substr($_text, $_i, '.$block_size.');
                            if (strlen($_block) > strlen($_buffer["ciphertext"])) {
                                $in = $_xor;
                                '.$encrypt_block.'
                                $self->_increment_str($_xor);
                                $_buffer["ciphertext"].= $in;
                            }
                            $_key = $self->_string_shift($_buffer["ciphertext"], '.$block_size.');
                            $_ciphertext.= $_block ^ $_key;
                        }
                    } else {
                        for ($_i = 0; $_i < $_plaintext_len; $_i+= '.$block_size.') {
                            $_block = substr($_text, $_i, '.$block_size.');
                            $in = $_xor;
                            '.$encrypt_block.'
                            $self->_increment_str($_xor);
                            $_key = $in;
                            $_ciphertext.= $_block ^ $_key;
                        }
                    }
                    if ($self->continuousBuffer) {
                        $self->encryptIV = $_xor;
                        if ($_start = $_plaintext_len % '.$block_size.') {
                            $_buffer["ciphertext"] = substr($_key, $_start) . $_buffer["ciphertext"];
                        }
                    }

                    return $_ciphertext;
                ';

                $decrypt = $init_encrypt . '
                    $_plaintext = "";
                    $_ciphertext_len = strlen($_text);
                    $_xor = $self->decryptIV;
                    $_buffer = &$self->debuffer;

                    if (strlen($_buffer["ciphertext"])) {
                        for ($_i = 0; $_i < $_ciphertext_len; $_i+= '.$block_size.') {
                            $_block = substr($_text, $_i, '.$block_size.');
                            if (strlen($_block) > strlen($_buffer["ciphertext"])) {
                                $in = $_xor;
                                '.$encrypt_block.'
                                $self->_increment_str($_xor);
                                $_buffer["ciphertext"].= $in;
                            }
                            $_key = $self->_string_shift($_buffer["ciphertext"], '.$block_size.');
                            $_plaintext.= $_block ^ $_key;
                        }
                    } else {
                        for ($_i = 0; $_i < $_ciphertext_len; $_i+= '.$block_size.') {
                            $_block = substr($_text, $_i, '.$block_size.');
                            $in = $_xor;
                            '.$encrypt_block.'
                            $self->_increment_str($_xor);
                            $_key = $in;
                            $_plaintext.= $_block ^ $_key;
                        }
                    }
                    if ($self->continuousBuffer) {
                        $self->decryptIV = $_xor;
                        if ($_start = $_ciphertext_len % '.$block_size.') {
                            $_buffer["ciphertext"] = substr($_key, $_start) . $_buffer["ciphertext"];
                        }
                    }

                    return $_plaintext;
                    ';
                break;
            case self::MODE_CFB:
                $encrypt = $init_encrypt . '
                    $_ciphertext = "";
                    $_buffer = &$self->enbuffer;

                    if ($self->continuousBuffer) {
                        $_iv = &$self->encryptIV;
                        $_pos = &$_buffer["pos"];
                    } else {
                        $_iv = $self->encryptIV;
                        $_pos = 0;
                    }
                    $_len = strlen($_text);
                    $_i = 0;
                    if ($_pos) {
                        $_orig_pos = $_pos;
                        $_max = '.$block_size.' - $_pos;
                        if ($_len >= $_max) {
                            $_i = $_max;
                            $_len-= $_max;
                            $_pos = 0;
                        } else {
                            $_i = $_len;
                            $_pos+= $_len;
                            $_len = 0;
                        }
                        $_ciphertext = substr($_iv, $_orig_pos) ^ $_text;
                        $_iv = substr_replace($_iv, $_ciphertext, $_orig_pos, $_i);
                    }
                    while ($_len >= '.$block_size.') {
                        $in = $_iv;
                        '.$encrypt_block.';
                        $_iv = $in ^ substr($_text, $_i, '.$block_size.');
                        $_ciphertext.= $_iv;
                        $_len-= '.$block_size.';
                        $_i+= '.$block_size.';
                    }
                    if ($_len) {
                        $in = $_iv;
                        '.$encrypt_block.'
                        $_iv = $in;
                        $_block = $_iv ^ substr($_text, $_i);
                        $_iv = substr_replace($_iv, $_block, 0, $_len);
                        $_ciphertext.= $_block;
                        $_pos = $_len;
                    }
                    return $_ciphertext;
                ';

                $decrypt = $init_encrypt . '
                    $_plaintext = "";
                    $_buffer = &$self->debuffer;

                    if ($self->continuousBuffer) {
                        $_iv = &$self->decryptIV;
                        $_pos = &$_buffer["pos"];
                    } else {
                        $_iv = $self->decryptIV;
                        $_pos = 0;
                    }
                    $_len = strlen($_text);
                    $_i = 0;
                    if ($_pos) {
                        $_orig_pos = $_pos;
                        $_max = '.$block_size.' - $_pos;
                        if ($_len >= $_max) {
                            $_i = $_max;
                            $_len-= $_max;
                            $_pos = 0;
                        } else {
                            $_i = $_len;
                            $_pos+= $_len;
                            $_len = 0;
                        }
                        $_plaintext = substr($_iv, $_orig_pos) ^ $_text;
                        $_iv = substr_replace($_iv, substr($_text, 0, $_i), $_orig_pos, $_i);
                    }
                    while ($_len >= '.$block_size.') {
                        $in = $_iv;
                        '.$encrypt_block.'
                        $_iv = $in;
                        $cb = substr($_text, $_i, '.$block_size.');
                        $_plaintext.= $_iv ^ $cb;
                        $_iv = $cb;
                        $_len-= '.$block_size.';
                        $_i+= '.$block_size.';
                    }
                    if ($_len) {
                        $in = $_iv;
                        '.$encrypt_block.'
                        $_iv = $in;
                        $_plaintext.= $_iv ^ substr($_text, $_i);
                        $_iv = substr_replace($_iv, substr($_text, $_i), 0, $_len);
                        $_pos = $_len;
                    }

                    return $_plaintext;
                    ';
                break;
            case self::MODE_CFB8:
                $encrypt = $init_encrypt . '
                    $_ciphertext = "";
                    $_len = strlen($_text);
                    $_iv = $self->encryptIV;

                    for ($_i = 0; $_i < $_len; ++$_i) {
                        $in = $_iv;
                        '.$encrypt_block.'
                        $_ciphertext.= ($_c = $_text[$_i] ^ $in);
                        $_iv = substr($_iv, 1) . $_c;
                    }

                    if ($self->continuousBuffer) {
                        if ($_len >= '.$block_size.') {
                            $self->encryptIV = substr($_ciphertext, -'.$block_size.');
                        } else {
                            $self->encryptIV = substr($self->encryptIV, $_len - '.$block_size.') . substr($_ciphertext, -$_len);
                        }
                    }

                    return $_ciphertext;
                    ';
                $decrypt = $init_encrypt . '
                    $_plaintext = "";
                    $_len = strlen($_text);
                    $_iv = $self->decryptIV;

                    for ($_i = 0; $_i < $_len; ++$_i) {
                        $in = $_iv;
                        '.$encrypt_block.'
                        $_plaintext.= $_text[$_i] ^ $in;
                        $_iv = substr($_iv, 1) . $_text[$_i];
                    }

                    if ($self->continuousBuffer) {
                        if ($_len >= '.$block_size.') {
                            $self->decryptIV = substr($_text, -'.$block_size.');
                        } else {
                            $self->decryptIV = substr($self->decryptIV, $_len - '.$block_size.') . substr($_text, -$_len);
                        }
                    }

                    return $_plaintext;
                    ';
                break;
            case self::MODE_OFB8:
                $encrypt = $init_encrypt . '
                    $_ciphertext = "";
                    $_len = strlen($_text);
                    $_iv = $self->encryptIV;

                    for ($_i = 0; $_i < $_len; ++$_i) {
                        $in = $_iv;
                        '.$encrypt_block.'
                        $_ciphertext.= $_text[$_i] ^ $in;
                        $_iv = substr($_iv, 1) . $in[0];
                    }

                    if ($self->continuousBuffer) {
                        $self->encryptIV = $_iv;
                    }

                    return $_ciphertext;
                    ';
                $decrypt = $init_encrypt . '
                    $_plaintext = "";
                    $_len = strlen($_text);
                    $_iv = $self->decryptIV;

                    for ($_i = 0; $_i < $_len; ++$_i) {
                        $in = $_iv;
                        '.$encrypt_block.'
                        $_plaintext.= $_text[$_i] ^ $in;
                        $_iv = substr($_iv, 1) . $in[0];
                    }

                    if ($self->continuousBuffer) {
                        $self->decryptIV = $_iv;
                    }

                    return $_plaintext;
                    ';
                break;
            case self::MODE_OFB:
                $encrypt = $init_encrypt . '
                    $_ciphertext = "";
                    $_plaintext_len = strlen($_text);
                    $_xor = $self->encryptIV;
                    $_buffer = &$self->enbuffer;

                    if (strlen($_buffer["xor"])) {
                        for ($_i = 0; $_i < $_plaintext_len; $_i+= '.$block_size.') {
                            $_block = substr($_text, $_i, '.$block_size.');
                            if (strlen($_block) > strlen($_buffer["xor"])) {
                                $in = $_xor;
                                '.$encrypt_block.'
                                $_xor = $in;
                                $_buffer["xor"].= $_xor;
                            }
                            $_key = $self->_string_shift($_buffer["xor"], '.$block_size.');
                            $_ciphertext.= $_block ^ $_key;
                        }
                    } else {
                        for ($_i = 0; $_i < $_plaintext_len; $_i+= '.$block_size.') {
                            $in = $_xor;
                            '.$encrypt_block.'
                            $_xor = $in;
                            $_ciphertext.= substr($_text, $_i, '.$block_size.') ^ $_xor;
                        }
                        $_key = $_xor;
                    }
                    if ($self->continuousBuffer) {
                        $self->encryptIV = $_xor;
                        if ($_start = $_plaintext_len % '.$block_size.') {
                             $_buffer["xor"] = substr($_key, $_start) . $_buffer["xor"];
                        }
                    }
                    return $_ciphertext;
                    ';

                $decrypt = $init_encrypt . '
                    $_plaintext = "";
                    $_ciphertext_len = strlen($_text);
                    $_xor = $self->decryptIV;
                    $_buffer = &$self->debuffer;

                    if (strlen($_buffer["xor"])) {
                        for ($_i = 0; $_i < $_ciphertext_len; $_i+= '.$block_size.') {
                            $_block = substr($_text, $_i, '.$block_size.');
                            if (strlen($_block) > strlen($_buffer["xor"])) {
                                $in = $_xor;
                                '.$encrypt_block.'
                                $_xor = $in;
                                $_buffer["xor"].= $_xor;
                            }
                            $_key = $self->_string_shift($_buffer["xor"], '.$block_size.');
                            $_plaintext.= $_block ^ $_key;
                        }
                    } else {
                        for ($_i = 0; $_i < $_ciphertext_len; $_i+= '.$block_size.') {
                            $in = $_xor;
                            '.$encrypt_block.'
                            $_xor = $in;
                            $_plaintext.= substr($_text, $_i, '.$block_size.') ^ $_xor;
                        }
                        $_key = $_xor;
                    }
                    if ($self->continuousBuffer) {
                        $self->decryptIV = $_xor;
                        if ($_start = $_ciphertext_len % '.$block_size.') {
                             $_buffer["xor"] = substr($_key, $_start) . $_buffer["xor"];
                        }
                    }
                    return $_plaintext;
                    ';
                break;
            case self::MODE_STREAM:
                $encrypt = $init_encrypt . '
                    $_ciphertext = "";
                    '.$encrypt_block.'
                    return $_ciphertext;
                    ';
                $decrypt = $init_decrypt . '
                    $_plaintext = "";
                    '.$decrypt_block.'
                    return $_plaintext;
                    ';
                break;
            // case self::MODE_CBC:
            default:
                $encrypt = $init_encrypt . '
                    $_ciphertext = "";
                    $_plaintext_len = strlen($_text);

                    $in = $self->encryptIV;

                    for ($_i = 0; $_i < $_plaintext_len; $_i+= '.$block_size.') {
                        $in = substr($_text, $_i, '.$block_size.') ^ $in;
                        '.$encrypt_block.'
                        $_ciphertext.= $in;
                    }

                    if ($self->continuousBuffer) {
                        $self->encryptIV = $in;
                    }

                    return $_ciphertext;
                    ';

                $decrypt = $init_decrypt . '
                    $_plaintext = "";
                    $_text = str_pad($_text, strlen($_text) + ('.$block_size.' - strlen($_text) % '.$block_size.') % '.$block_size.', chr(0));
                    $_ciphertext_len = strlen($_text);

                    $_iv = $self->decryptIV;

                    for ($_i = 0; $_i < $_ciphertext_len; $_i+= '.$block_size.') {
                        $in = $_block = substr($_text, $_i, '.$block_size.');
                        '.$decrypt_block.'
                        $_plaintext.= $in ^ $_iv;
                        $_iv = $_block;
                    }

                    if ($self->continuousBuffer) {
                        $self->decryptIV = $_iv;
                    }

                    return $self->_unpad($_plaintext);
                    ';
                break;
        }

        // Create the $inline function and return its name as string. Ready to run!
        eval('$func = function ($_action, &$self, $_text) { ' . $init_crypt . 'if ($_action == "encrypt") { ' . $encrypt . ' } else { ' . $decrypt . ' } };');
        return $func;
    }

    /**
     * Holds the lambda_functions table (classwide)
     *
     * Each name of the lambda function, created from
     * _setupInlineCrypt() && _createInlineCryptFunction()
     * is stored, classwide (!), here for reusing.
     *
     * The string-based index of $function is a classwide
     * unique value representing, at least, the $mode of
     * operation (or more... depends of the optimizing level)
     * for which $mode the lambda function was created.
     *
     * @access private
     * @return array &$functions
     */
    function &_getLambdaFunctions()
    {
        static $functions = array();
        return $functions;
    }

    /**
     * Generates a digest from $bytes
     *
     * @see self::_setupInlineCrypt()
     * @access private
     * @param string $bytes
     * @return string
     */
    function _hashInlineCryptFunction($bytes)
    {
        if (!isset(self::$WHIRLPOOL_AVAILABLE)) {
            self::$WHIRLPOOL_AVAILABLE = extension_loaded('hash') && in_array('whirlpool', hash_algos());
        }

        $result = '';
        $hash = $bytes;

        switch (true) {
            case self::$WHIRLPOOL_AVAILABLE:
                foreach (str_split($bytes, 64) as $t) {
                    $hash = hash('whirlpool', $hash, true);
                    $result .= $t ^ $hash;
                }
                return $result . hash('whirlpool', $hash, true);
            default:
                $len = strlen($bytes);
                for ($i = 0; $i < $len; $i+=20) {
                    $t = substr($bytes, $i, 20);
                    $hash = pack('H*', sha1($hash));
                    $result .= $t ^ $hash;
                }
                return $result . pack('H*', sha1($hash));
        }
    }

    /**
     * Convert float to int
     *
     * On ARM CPUs converting floats to ints doesn't always work
     *
     * @access private
     * @param string $x
     * @return int
     */
    function safe_intval($x)
    {
        if (is_int($x)) {
            return $x;
        }
        return (fmod($x, 0x80000000) & 0x7FFFFFFF) |
            ((fmod(floor($x / 0x80000000), 2) & 1) << 31);
    }

    /**
     * eval()'able string for in-line float to int
     *
     * @access private
     * @return string
     */
    function safe_intval_inline()
    {
        if (CRYPT_BASE_USE_REG_INTVAL) {
            return PHP_INT_SIZE == 4 ? 'intval(%s)' : '%s';
        }

        $safeint = '(is_int($temp = %s) ? $temp : (fmod($temp, 0x80000000) & 0x7FFFFFFF) | ';
        return $safeint . '((fmod(floor($temp / 0x80000000), 2) & 1) << 31))';
    }

    /**
     * Dummy error handler to suppress mcrypt errors
     *
     * @access private
     */
    function do_nothing()
    {
    }

    /**
     * Is the continuous buffer enabled?
     *
     * @access public
     * @return boolean
     */
    function continuousBufferEnabled()
    {
        return $this->continuousBuffer;
    }
}
¿Qué es la limpieza dental de perros? - Clínica veterinaria


Es la eliminación del sarro y la placa adherida a la superficie de los dientes mediante un equipo de ultrasonidos que garantiza la integridad de las piezas dentales a la vez que elimina en profundidad cualquier resto de suciedad.

A continuación se procede al pulido de los dientes mediante una fresa especial que elimina la placa bacteriana y devuelve a los dientes el aspecto sano que deben tener.

Una vez terminado todo el proceso, se mantiene al perro en observación hasta que se despierta de la anestesia, bajo la atenta supervisión de un veterinario.

¿Cada cuánto tiempo tengo que hacerle una limpieza dental a mi perro?

A partir de cierta edad, los perros pueden necesitar una limpieza dental anual o bianual. Depende de cada caso. En líneas generales, puede decirse que los perros de razas pequeñas suelen acumular más sarro y suelen necesitar una atención mayor en cuanto a higiene dental.


Riesgos de una mala higiene


Los riesgos más evidentes de una mala higiene dental en los perros son los siguientes:

  • Cuando la acumulación de sarro no se trata, se puede producir una inflamación y retracción de las encías que puede descalzar el diente y provocar caídas.
  • Mal aliento (halitosis).
  • Sarro perros
  • Puede ir a más
  • Las bacterias de la placa pueden trasladarse a través del torrente circulatorio a órganos vitales como el corazón ocasionando problemas de endocarditis en las válvulas. Las bacterias pueden incluso acantonarse en huesos (La osteomielitis es la infección ósea, tanto cortical como medular) provocando mucho dolor y una artritis séptica).

¿Cómo se forma el sarro?

El sarro es la calcificación de la placa dental. Los restos de alimentos, junto con las bacterias presentes en la boca, van a formar la placa bacteriana o placa dental. Si la placa no se retira, al mezclarse con la saliva y los minerales presentes en ella, reaccionará formando una costra. La placa se calcifica y se forma el sarro.

El sarro, cuando se forma, es de color blanquecino pero a medida que pasa el tiempo se va poniendo amarillo y luego marrón.

Síntomas de una pobre higiene dental
La señal más obvia de una mala salud dental canina es el mal aliento.

Sin embargo, a veces no es tan fácil de detectar
Y hay perros que no se dejan abrir la boca por su dueño. Por ejemplo…

Recientemente nos trajeron a la clínica a un perro que parpadeaba de un ojo y decía su dueño que le picaba un lado de la cara. Tenía molestias y dificultad para comer, lo que había llevado a sus dueños a comprarle comida blanda (que suele ser un poco más cara y llevar más contenido en grasa) durante medio año. Después de una exploración oftalmológica, nos dimos cuenta de que el ojo tenía una úlcera en la córnea probablemente de rascarse . Además, el canto lateral del ojo estaba inflamado. Tenía lo que en humanos llamamos flemón pero como era un perro de pelo largo, no se le notaba a simple vista. Al abrirle la boca nos llamó la atención el ver una muela llena de sarro. Le realizamos una radiografía y encontramos una fístula que llegaba hasta la parte inferior del ojo.

Le tuvimos que extraer la muela. Tras esto, el ojo se curó completamente con unos colirios y una lentilla protectora de úlcera. Afortunadamente, la úlcera no profundizó y no perforó el ojo. Ahora el perro come perfectamente a pesar de haber perdido una muela.

¿Cómo mantener la higiene dental de tu perro?
Hay varias maneras de prevenir problemas derivados de la salud dental de tu perro.

Limpiezas de dientes en casa
Es recomendable limpiar los dientes de tu perro semanal o diariamente si se puede. Existe una gran variedad de productos que se pueden utilizar:

Pastas de dientes.
Cepillos de dientes o dedales para el dedo índice, que hacen más fácil la limpieza.
Colutorios para echar en agua de bebida o directamente sobre el diente en líquido o en spray.

En la Clínica Tus Veterinarios enseñamos a nuestros clientes a tomar el hábito de limpiar los dientes de sus perros desde que son cachorros. Esto responde a nuestro compromiso con la prevención de enfermedades caninas.

Hoy en día tenemos muchos clientes que limpian los dientes todos los días a su mascota, y como resultado, se ahorran el dinero de hacer limpiezas dentales profesionales y consiguen una mejor salud de su perro.


Limpiezas dentales profesionales de perros y gatos

Recomendamos hacer una limpieza dental especializada anualmente. La realizamos con un aparato de ultrasonidos que utiliza agua para quitar el sarro. Después, procedemos a pulir los dientes con un cepillo de alta velocidad y una pasta especial. Hacemos esto para proteger el esmalte.

La frecuencia de limpiezas dentales necesaria varía mucho entre razas. En general, las razas grandes tienen buena calidad de esmalte, por lo que no necesitan hacerlo tan a menudo e incluso pueden pasarse la vida sin requerir una limpieza. Sin embargo, razas pequeñas como el Yorkshire o el Maltés, deben hacérselas todos los años desde cachorros si se quiere conservar sus piezas dentales.

Otro factor fundamental es la calidad del pienso. Algunas marcas han diseñado croquetas que limpian la superficie del diente y de la muela al masticarse.

Ultrasonido para perros

¿Se necesita anestesia para las limpiezas dentales de perros y gatos?

La limpieza dental en perros no es una técnica que pueda practicarse sin anestesia general , aunque hay veces que los propietarios no quieren anestesiar y si tiene poco sarro y el perro es muy bueno se puede intentar…… , pero no se va a poder pulir ni acceder a todas la zona de la boca …. Además los limpiadores dentales van a irrigar agua y hay riesgo de aspiración a vías respiratorias si no se realiza una anestesia correcta con intubación traqueal . En resumen , sin anestesia no se va hacer una correcta limpieza dental.

Tampoco sirve la sedación ya que necesitamos que el animal esté totalmente quieto, y el veterinario tenga un acceso completo a todas sus piezas dentales y encías.

Alimentos para la limpieza dental

Hay que tener cierto cuidado a la hora de comprar determinados alimentos porque no todos son saludables. Algunos tienen demasiado contenido graso, que en exceso puede causar problemas cardiovasculares y obesidad.

Los mejores alimentos para los dientes son aquellos que están elaborados por empresas farmacéuticas y llevan componentes químicos con tratamientos específicos para el diente del perro. Esto implica no solo limpieza a través de la acción mecánica de morder sino también un tratamiento antibacteriano para prevenir el sarro.

Conclusión

Si eres como la mayoría de dueños, por falta de tiempo , es probable que no estés prestando la suficiente atención a la limpieza dental de tu perro. Por eso te animamos a que comiences a limpiar los dientes de tu perro y consideres atender a su higiene bucal con frecuencia.

Estas simples medidas pueden conllevar a que tu perro tenga una vida más larga y mucho más saludable.

Si te resulta imposible introducir un cepillo de dientes a tu perro en la boca, pásate con él por clínica Tus Veterinarios y te explicamos cómo hacerlo.

Necesitas hacer una limpieza dental profesional a tu mascota?
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