MDECRYPT_GENERIC(3) 1 MDECRYPT_GENERIC(3)
mdecrypt_generic - Decrypts data
SYNOPSIS
string mdecrypt_generic (resource $td, string $data)
DESCRIPTION
This function decrypts data. Note that the length of the returned string can in fact be longer than the unencrypted string, due to the
padding of the data.
PARAMETERS
o $td
- An encryption descriptor returned by mcrypt_module_open(3)
o $data
- Encrypted data.
EXAMPLES
Example #1
mdecrypt_generic(3) Example
<?php
/* Data */
$key = 'this is a very long key, even too long for the cipher';
$plain_text = 'very important data';
/* Open module, and create IV */
$td = mcrypt_module_open('des', '', 'ecb', '');
$key = substr($key, 0, mcrypt_enc_get_key_size($td));
$iv_size = mcrypt_enc_get_iv_size($td);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
/* Initialize encryption handle */
if (mcrypt_generic_init($td, $key, $iv) != -1) {
/* Encrypt data */
$c_t = mcrypt_generic($td, $plain_text);
mcrypt_generic_deinit($td);
/* Reinitialize buffers for decryption */
mcrypt_generic_init($td, $key, $iv);
$p_t = mdecrypt_generic($td, $c_t);
/* Clean up */
mcrypt_generic_deinit($td);
mcrypt_module_close($td);
}
if (strncmp($p_t, $plain_text, strlen($plain_text)) == 0) {
echo "ok
";
} else {
echo "error
";
}
?>
The example above shows how to check if the data before the encryption is the same as the data after the decryption. It is very important
to reinitialize the encryption buffer with mcrypt_generic_init(3) before you try to decrypt the data.
The decryption handle should always be initialized with mcrypt_generic_init(3) with a key and an IV before calling this function. Where
the encryption is done, you should free the encryption buffers by calling mcrypt_generic_deinit(3). See mcrypt_module_open(3) for an exam-
ple.
SEE ALSO
mcrypt_generic(3), mcrypt_generic_init(3), mcrypt_generic_deinit(3).
PHP Documentation Group MDECRYPT_GENERIC(3)
