/**
  * Encrypt the data
  *
  * @param string $data Data string to encrypt
  * @param string $key  Encryption key
  * @param string $mode Default mode (openssl or mcrypt)
  *
  * @return string Encrypted data string.
  */
 public function encrypt($data, $key, $mode = 'openssl')
 {
     if ($mode == 'openssl' && extension_loaded('openssl') && in_array('aes-256-cbc', openssl_get_cipher_methods())) {
         return $this->encryptOpenSsl($data, $key);
     }
     if ($mode != 'raw' && function_exists('mcrypt_create_iv') && mcrypt_get_cipher_name(MCRYPT_RIJNDAEL_128) !== false) {
         return $this->encryptMcrypt($data, $key);
     }
     throw new EncException('Either "openssl" PHP extension with "aes-256-cbc" cypher' . ' or "mcrypt" PHP extension with "MCRYPT_RIJNDAEL_128" cypher is required for AES encryption');
 }

 /**
  * Set document protection
  * Remark: the protection against modification is for people who have the full Acrobat product.
  * If you don't set any password, the document will open as usual. If you set a user password, the PDF viewer will ask for it before displaying the document. The master password, if different from the user one, can be used to get full access.
  * Note: protecting a document requires to encrypt it, which increases the processing time a lot. This can cause a PHP time-out in some cases, especially if the document contains images or fonts.
  * @param $permissions (Array) the set of permissions (specify the ones you want to block):<ul><li>print : Print the document;</li><li>modify : Modify the contents of the document by operations other than those controlled by 'fill-forms', 'extract' and 'assemble';</li><li>copy : Copy or otherwise extract text and graphics from the document;</li><li>annot-forms : Add or modify text annotations, fill in interactive form fields, and, if 'modify' is also set, create or modify interactive form fields (including signature fields);</li><li>fill-forms : Fill in existing interactive form fields (including signature fields), even if 'annot-forms' is not specified;</li><li>extract : Extract text and graphics (in support of accessibility to users with disabilities or for other purposes);</li><li>assemble : Assemble the document (insert, rotate, or delete pages and create bookmarks or thumbnail images), even if 'modify' is not set;</li><li>print-high : Print the document to a representation from which a faithful digital copy of the PDF content could be generated. When this is not set, printing is limited to a low-level representation of the appearance, possibly of degraded quality.</li><li>owner : (inverted logic - only for public-key) when set permits change of encryption and enables all other permissions.</li></ul>
  * @param $user_pass (String) user password. Empty by default.
  * @param $owner_pass (String) owner password. If not specified, a random value is used.
  * @param $mode (int) encryption strength: 0 = RC4 40 bit; 1 = RC4 128 bit; 2 = AES 128 bit; 3 = AES 256 bit.
  * @param $pubkeys (String) array of recipients containing public-key certificates ('c') and permissions ('p'). For example: array(array('c' => 'file://../examples/data/cert/tcpdf.crt', 'p' => array('print')))
  * @public
  * @since 2.0.000 (2008-01-02)
  * @author Nicola Asuni
  */
 public function SetProtection($permissions = array('print', 'modify', 'copy', 'annot-forms', 'fill-forms', 'extract', 'assemble', 'print-high'), $user_pass = '', $owner_pass = null, $mode = 0, $pubkeys = null)
 {
     if ($this->pdfa_mode) {
         // encryption is not allowed in PDF/A mode
         return;
     }
     $this->encryptdata['protection'] = TCPDF_STATIC::getUserPermissionCode($permissions, $mode);
     if ($pubkeys !== null and is_array($pubkeys)) {
         // public-key mode
         $this->encryptdata['pubkeys'] = $pubkeys;
         if ($mode == 0) {
             // public-Key Security requires at least 128 bit
             $mode = 1;
         }
         if (!function_exists('openssl_pkcs7_encrypt')) {
             $this->Error('Public-Key Security requires openssl library.');
         }
         // Set Public-Key filter (availabe are: Entrust.PPKEF, Adobe.PPKLite, Adobe.PubSec)
         $this->encryptdata['pubkey'] = true;
         $this->encryptdata['Filter'] = 'Adobe.PubSec';
         $this->encryptdata['StmF'] = 'DefaultCryptFilter';
         $this->encryptdata['StrF'] = 'DefaultCryptFilter';
     } else {
         // standard mode (password mode)
         $this->encryptdata['pubkey'] = false;
         $this->encryptdata['Filter'] = 'Standard';
         $this->encryptdata['StmF'] = 'StdCF';
         $this->encryptdata['StrF'] = 'StdCF';
     }
     if ($mode > 1) {
         // AES
         if (!extension_loaded('mcrypt')) {
             $this->Error('AES encryption requires mcrypt library (http://www.php.net/manual/en/mcrypt.requirements.php).');
         }
         if (mcrypt_get_cipher_name(MCRYPT_RIJNDAEL_128) === false) {
             $this->Error('AES encryption requires MCRYPT_RIJNDAEL_128 cypher.');
         }
         if ($mode == 3 and !function_exists('hash')) {
             // the Hash extension requires no external libraries and is enabled by default as of PHP 5.1.2.
             $this->Error('AES 256 encryption requires HASH Message Digest Framework (http://www.php.net/manual/en/book.hash.php).');
         }
     }
     if ($owner_pass === null) {
         $owner_pass = md5(TCPDF_STATIC::getRandomSeed());
     }
     $this->encryptdata['user_password'] = $user_pass;
     $this->encryptdata['owner_password'] = $owner_pass;
     $this->encryptdata['mode'] = $mode;
     switch ($mode) {
         case 0:
             // RC4 40 bit
             $this->encryptdata['V'] = 1;
             $this->encryptdata['Length'] = 40;
             $this->encryptdata['CF']['CFM'] = 'V2';
             break;
         case 1:
             // RC4 128 bit
             $this->encryptdata['V'] = 2;
             $this->encryptdata['Length'] = 128;
             $this->encryptdata['CF']['CFM'] = 'V2';
             if ($this->encryptdata['pubkey']) {
                 $this->encryptdata['SubFilter'] = 'adbe.pkcs7.s4';
                 $this->encryptdata['Recipients'] = array();
             }
             break;
         case 2:
             // AES 128 bit
             $this->encryptdata['V'] = 4;
             $this->encryptdata['Length'] = 128;
             $this->encryptdata['CF']['CFM'] = 'AESV2';
             $this->encryptdata['CF']['Length'] = 128;
             if ($this->encryptdata['pubkey']) {
                 $this->encryptdata['SubFilter'] = 'adbe.pkcs7.s5';
                 $this->encryptdata['Recipients'] = array();
             }
             break;
         case 3:
             // AES 256 bit
             $this->encryptdata['V'] = 5;
             $this->encryptdata['Length'] = 256;
             $this->encryptdata['CF']['CFM'] = 'AESV3';
             $this->encryptdata['CF']['Length'] = 256;
             if ($this->encryptdata['pubkey']) {
                 $this->encryptdata['SubFilter'] = 'adbe.pkcs7.s5';
                 $this->encryptdata['Recipients'] = array();
             }
//.........这里部分代码省略.........

 /**
  * Returns the name of the opened algorithm.
  *
  * @param McryptResource $td
  * @return string
  * @deprecated
  */
 function mcrypt_enc_get_algorithms_name($td)
 {
     if (!td instanceof McryptResource) {
         return false;
     }
     return mcrypt_get_cipher_name($td->getMode());
 }

 /**
  * Set document protection
  * Remark: the protection against modification is for people who have the full Acrobat product.
  * If you don't set any password, the document will open as usual. If you set a user password, the PDF viewer will ask for it before displaying the document. The master password, if different from the user one, can be used to get full access.
  * Note: protecting a document requires to encrypt it, which increases the processing time a lot. This can cause a PHP time-out in some cases, especially if the document contains images or fonts.
  * @param Array $permissions the set of permissions (specify the ones you want to block):<ul><li>print : Print the document;</li><li>modify : Modify the contents of the document by operations other than those controlled by 'fill-forms', 'extract' and 'assemble';</li><li>copy : Copy or otherwise extract text and graphics from the document;</li><li>annot-forms : Add or modify text annotations, fill in interactive form fields, and, if 'modify' is also set, create or modify interactive form fields (including signature fields);</li><li>fill-forms : Fill in existing interactive form fields (including signature fields), even if 'annot-forms' is not specified;</li><li>extract : Extract text and graphics (in support of accessibility to users with disabilities or for other purposes);</li><li>assemble : Assemble the document (insert, rotate, or delete pages and create bookmarks or thumbnail images), even if 'modify' is not set;</li><li>print-high : Print the document to a representation from which a faithful digital copy of the PDF content could be generated. When this is not set, printing is limited to a low-level representation of the appearance, possibly of degraded quality.</li><li>owner : (inverted logic - only for public-key) when set permits change of encryption and enables all other permissions.</li></ul>
  * @param String $user_pass user password. Empty by default.
  * @param String $owner_pass owner password. If not specified, a random value is used.
  * @param int $mode encryption strength: 0 = RC4 40 bit; 1 = RC4 128 bit; 2 = AES 128 bit.
  * @param String $pubkeys array of recipients containing public-key certificates ('c') and permissions ('p'). For example: array(array('c' => 'file://../tcpdf.crt', 'p' => array('print')))
  * @access public
  * @since 2.0.000 (2008-01-02)
  * @author Nicola Asuni
  */
 public function SetProtection($permissions = array('print', 'modify', 'copy', 'annot-forms', 'fill-forms', 'extract', 'assemble', 'print-high'), $user_pass = '', $owner_pass = null, $mode = 0, $pubkeys = null)
 {
     $protection = $this->getUserPermissionCode($permissions, $mode);
     if ($pubkeys !== null and is_array($pubkeys)) {
         // public-key mode
         $this->encryptdata['pubkeys'] = $pubkeys;
         if ($mode == 0) {
             // public-Key Security requires at least 128 bit
             $mode = 1;
         }
         if (!function_exists('openssl_pkcs7_encrypt')) {
             $this->Error('Public-Key Security requires openssl library.');
         }
         // Set Public-Key filter (availabe are: Entrust.PPKEF, Adobe.PPKLite, Adobe.PubSec)
         $this->encryptdata['pubkey'] = true;
         $this->encryptdata['Filter'] = 'Adobe.PubSec';
         $this->encryptdata['StmF'] = 'DefaultCryptFilter';
         $this->encryptdata['StrF'] = 'DefaultCryptFilter';
     } else {
         // standard mode (password mode)
         $this->encryptdata['pubkey'] = false;
         $this->encryptdata['Filter'] = 'Standard';
         $this->encryptdata['StmF'] = 'StdCF';
         $this->encryptdata['StrF'] = 'StdCF';
     }
     if ($mode > 1) {
         // AES
         if (!extension_loaded('mcrypt')) {
             $this->Error('AES encryption requires mcrypt library.');
         }
         if (mcrypt_get_cipher_name(MCRYPT_RIJNDAEL_128) === false) {
             $this->Error('AES encryption requires MCRYPT_RIJNDAEL_128 cypher.');
         }
     }
     if ($owner_pass === null) {
         $owner_pass = uniqid('' . rand());
     }
     $this->encryptdata['mode'] = $mode;
     switch ($mode) {
         case 0:
             // RC4 40 bit
             $this->encryptdata['V'] = 1;
             $this->encryptdata['Length'] = 40;
             $this->encryptdata['CF']['CFM'] = 'V2';
             break;
         case 1:
             // RC4 128 bit
             $this->encryptdata['V'] = 2;
             $this->encryptdata['Length'] = 128;
             $this->encryptdata['CF']['CFM'] = 'V2';
             if ($this->encryptdata['pubkey']) {
                 $this->encryptdata['SubFilter'] = 'adbe.pkcs7.s4';
                 $this->encryptdata['Recipients'] = array();
             }
             break;
         case 2:
             // AES 128 bit
             $this->encryptdata['V'] = 4;
             $this->encryptdata['Length'] = 128;
             $this->encryptdata['CF']['CFM'] = 'AESV2';
             if ($this->encryptdata['pubkey']) {
                 $this->encryptdata['SubFilter'] = 'adbe.pkcs7.s5';
                 $this->encryptdata['Recipients'] = array();
             }
             break;
     }
     $this->encrypted = true;
     $this->encryptdata['fileid'] = $this->convertHexStringToString($this->file_id);
     $this->_generateencryptionkey($user_pass, $owner_pass, $protection);
 }

<?php

echo mcrypt_get_cipher_name(MCRYPT_RIJNDAEL_256) . "\n";
echo mcrypt_get_cipher_name(MCRYPT_RC2) . "\n";
echo mcrypt_get_cipher_name(MCRYPT_ARCFOUR) . "\n";
echo mcrypt_get_cipher_name(MCRYPT_WAKE) . "\n";

$key = "123456789012345678901234567890123456789012345678901234567890";
$CC = "4007000000027";
$encrypted = mcrypt_ecb(MCRYPT_RIJNDAEL_128, substr($key, 0, 32), $CC, MCRYPT_ENCRYPT, substr($key, 32, 16));
$decrypted = mcrypt_ecb(MCRYPT_RIJNDAEL_128, substr($key, 0, 32), $encrypted, MCRYPT_DECRYPT, substr($key, 32, 16));
VERIFY($encrypted !== $decrypted);
VS(trim((string) $decrypted), $CC);
//////////////////////////////////////////////////////////////////////
$key = "123456789012345678901234567890123456789012345678901234567890";
$CC = "4007000000027";
$encrypted = mcrypt_ofb(MCRYPT_RIJNDAEL_128, substr($key, 0, 32), $CC, MCRYPT_ENCRYPT, substr($key, 32, 16));
$decrypted = mcrypt_ofb(MCRYPT_RIJNDAEL_128, substr($key, 0, 32), $encrypted, MCRYPT_DECRYPT, substr($key, 32, 16));
VERIFY($encrypted !== $decrypted);
VS($decrypted, $CC);
//////////////////////////////////////////////////////////////////////
VS(mcrypt_get_block_size("tripledes", "ecb"), 8);
VS(mcrypt_get_cipher_name(MCRYPT_TRIPLEDES), "3DES");
VS(mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB), 16);
VS(mcrypt_get_iv_size("des", "ecb"), 8);
VS(mcrypt_get_key_size("tripledes", "ecb"), 24);
$td = mcrypt_module_open("cast-256", "", "cfb", "");
VS(mcrypt_enc_get_algorithms_name($td), "CAST-256");
$td = mcrypt_module_open("tripledes", "", "ecb", "");
VS(mcrypt_enc_get_block_size($td), 8);
$td = mcrypt_module_open("cast-256", "", "cfb", "");
VS(mcrypt_enc_get_iv_size($td), 16);
$td = mcrypt_module_open("tripledes", "", "ecb", "");
VS(mcrypt_enc_get_key_size($td), 24);
$td = mcrypt_module_open("cast-256", "", "cfb", "");
VS(mcrypt_enc_get_modes_name($td), "CFB");
$td = mcrypt_module_open("rijndael-256", "", "ecb", "");
VS(mcrypt_enc_get_supported_key_sizes($td), array(16, 24, 32));