mcrypt_get_iv_size(3) [php man page]

MCRYPT_GET_IV_SIZE(3)							 1						     MCRYPT_GET_IV_SIZE(3)

mcrypt_get_iv_size - Returns the size of the IV belonging to a specific cipher/mode combination

SYNOPSIS

       int mcrypt_get_iv_size (string  $cipher, string	$mode)

DESCRIPTION

	Gets the size of the IV belonging to a specific $cipher/$mode combination.

	It is more useful to use the mcrypt_enc_get_iv_size(3) function as this uses the resource returned by mcrypt_module_open(3).

PARAMETERS

	      o $cipher
		-One of the MCRYPT_ciphername constants, or the name of the algorithm as string.

	      o $mode
		-One  of  the MCRYPT_MODE_modename constants, or one of the following strings: "ecb", "cbc", "cfb", "ofb", "nofb" or "stream". The
		IV is ignored in ECB mode as this mode does not require it. You will need to have the same IV  (think:	starting  point)  both	at
		encryption and decryption stages, otherwise your encryption will fail.

RETURN VALUES

	Returns  the  size  of the Initialization Vector (IV) in bytes. On error the function returns FALSE. If the IV is ignored in the specified
       cipher/mode combination zero is returned.

EXAMPLES

       Example #1

	      mcrypt_get_iv_size(3) Example

	      <?php
		  echo mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB) . "
";

		  echo mcrypt_get_iv_size('des', 'ecb') . "
";
	      ?>

SEE ALSO

       mcrypt_get_block_size(3), mcrypt_enc_get_iv_size(3), mcrypt_create_iv(3).

PHP Documentation Group 												     MCRYPT_GET_IV_SIZE(3)

MCRYPT_MODULE_OPEN(3)							 1						     MCRYPT_MODULE_OPEN(3)

mcrypt_module_open - Opens the module of the algorithm and the mode to be used

SYNOPSIS

       resource mcrypt_module_open (string  $algorithm, string	$algorithm_directory, string  $mode, string  $mode_directory)

DESCRIPTION

	This  function	opens  the  module  of	the  algorithm	and the mode to be used. The name of the algorithm is specified in algorithm, e.g.
       "twofish" or is one of the MCRYPT_ciphername constants. The module is closed by calling mcrypt_module_close(3).

PARAMETERS

	      o $algorithm
		-One of the MCRYPT_ciphername constants, or the name of the algorithm as string.

	      o $algorithm_directory
		- The $algorithm_directory parameter is used to locate the encryption module. When you supply a directory name, it is  used.  When
		you set it to an empty string ( ""), the value set by the mcrypt.algorithms_dir php.ini directive is used. When it is not set, the
		default directory that is used is the one that was compiled into libmcrypt (usually /usr/local/lib/libmcrypt).

	      o $mode
		-One of the MCRYPT_MODE_modename constants, or one of the following strings: "ecb", "cbc", "cfb", "ofb", "nofb" or "stream".

	      o $mode_directory
		- The $mode_directory parameter is used to locate the encryption module. When you supply a directory name, it is  used.  When  you
		set  it to an empty string ( ""), the value set by the mcrypt.modes_dir php.ini directive is used. When it is not set, the default
		directory that is used is the one that was compiled-in into libmcrypt (usually /usr/local/lib/libmcrypt).

RETURN VALUES

	Normally it returns an encryption descriptor, or FALSE on error.

EXAMPLES

       Example #1

	      mcrypt_module_open(3) Examples

	      <?php
		  $td = mcrypt_module_open(MCRYPT_DES, '',
		      MCRYPT_MODE_ECB, '/usr/lib/mcrypt-modes');

		  $td = mcrypt_module_open('rijndael-256', '', 'ofb', '');
	      ?>

	The first line in the example above will try to open the DES cipher from the default  directory  and  the  ECB	mode  from  the  directory
       /usr/lib/mcrypt-modes.  The  second  example  uses  strings  as	name for the cipher and mode, this only works when the extension is linked
       against libmcrypt 2.4.x or 2.5.x.

       Example #2

	      Using mcrypt_module_open(3) in encryption

	      <?php
		  /* Open the cipher */
		  $td = mcrypt_module_open('rijndael-256', '', 'ofb', '');

		  /* Create the IV and determine the keysize length, use MCRYPT_RAND
		   * on Windows instead */
		  $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_DEV_RANDOM);
		  $ks = mcrypt_enc_get_key_size($td);

		  /* Create key */
		  $key = substr(md5('very secret key'), 0, $ks);

		  /* Intialize encryption */
		  mcrypt_generic_init($td, $key, $iv);

		  /* Encrypt data */
		  $encrypted = mcrypt_generic($td, 'This is very important data');

		  /* Terminate encryption handler */
		  mcrypt_generic_deinit($td);

		  /* Initialize encryption module for decryption */
		  mcrypt_generic_init($td, $key, $iv);

		  /* Decrypt encrypted string */
		  $decrypted = mdecrypt_generic($td, $encrypted);

		  /* Terminate decryption handle and close module */
		  mcrypt_generic_deinit($td);
		  mcrypt_module_close($td);

		  /* Show string */
		  echo trim($decrypted) . "
";
	      ?>

SEE ALSO

       mcrypt_module_close(3), mcrypt_generic(3), mdecrypt_generic(3), mcrypt_generic_init(3), mcrypt_generic_deinit(3).

PHP Documentation Group 												     MCRYPT_MODULE_OPEN(3)