mcrypt_get_key_size(3) [php man page]

MCRYPT_GET_KEY_SIZE(3)							 1						    MCRYPT_GET_KEY_SIZE(3)

mcrypt_get_key_size - Gets the key size of the specified cipher

SYNOPSIS

       int mcrypt_get_key_size (int  $cipher)

DESCRIPTION

       int mcrypt_get_key_size (string	$cipher, string  $mode)

	The first prototype is when linked against libmcrypt 2.2.x, the second when linked against libmcrypt 2.4.x or 2.5.x.

       mcrypt_get_key_size(3) is used to get the size of a key of the specified $cipher (in combination with an encryption mode).

	It is more useful to use the mcrypt_enc_get_key_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".

RETURN VALUES

	Returns the maximum supported key size of the algorithm in bytes or FALSE on failure.

EXAMPLES

       Example #1

	      mcrypt_get_key_size(3) Example

	      <?php
		  echo mcrypt_get_key_size('tripledes', 'ecb');
	      ?>

	       The example above shows how to use this function when linked against libmcrypt 2.4.x or 2.5.x.

	      The above example will output:

	      24

SEE ALSO

       mcrypt_get_block_size(3), mcrypt_enc_get_key_size(3), mcrypt_encrypt(3).

PHP Documentation Group 												    MCRYPT_GET_KEY_SIZE(3)

MCRYPT_ENCRYPT(3)							 1							 MCRYPT_ENCRYPT(3)

mcrypt_encrypt - Encrypts plaintext with given parameters

SYNOPSIS

       string mcrypt_encrypt (string  $cipher, string  $key, string  $data, string  $mode, [string  $iv])

DESCRIPTION

	Encrypts the data and returns it.

PARAMETERS

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

	      o $key
		-  The key with which the data will be encrypted. If it's smaller than the required keysize, it is padded with ' '. It is better
		not to use ASCII strings for keys.  It is recommended to use the mhash functions to create a key from a string.

	      o $data
		- The data that will be encrypted with the given $cipher and $mode. If the size of the data is not n * blocksize, the data will be
		padded with ' '.  The returned crypttext can be larger than the size of the data that was given by $data.

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

	      o $iv
		-Used  for  the initialization in CBC, CFB, OFB modes, and in some algorithms in STREAM mode. If you do not supply an IV, while it
		is needed for an algorithm, the function issues a warning and uses an IV with all its bytes set to " ".

RETURN VALUES

	Returns the encrypted data, as a string.

EXAMPLES

       Example #1

	      mcrypt_encrypt(3) Example

	      <?php
		  # --- ENCRYPTION ---

		  # the key should be random binary, use scrypt, bcrypt or PBKDF2 to
		  # convert a string into a key
		  # key is specified using hexadecimal
		  $key = pack('H*', "bcb04b7e103a0cd8b54763051cef08bc55abe029fdebae5e1d417e2ffb2a00a3");

		  # show key size use either 16, 24 or 32 byte keys for AES-128, 192
		  # and 256 respectively
		  $key_size =  strlen($key);
		  echo "Key size: " . $key_size . "
";

		  $plaintext = "This string was AES-256 / CBC / ZeroBytePadding encrypted.";

		  # create a random IV to use with CBC encoding
		  $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
		  $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);

		  # creates a cipher text compatible with AES (Rijndael block size = 128)
		  # to keep the text confidential
		  # only suitable for encoded input that never ends with value 00h
		  # (because of default zero padding)
		  $ciphertext = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key,
					       $plaintext, MCRYPT_MODE_CBC, $iv);

		  # prepend the IV for it to be available for decryption
		  $ciphertext = $iv . $ciphertext;

		  # encode the resulting cipher text so it can be represented by a string
		  $ciphertext_base64 = base64_encode($ciphertext);

		  echo	$ciphertext_base64 . "
";

		  # === WARNING ===

		  # Resulting cipher text has no integrity or authenticity added
		  # and is not protected against padding oracle attacks.

		  # --- DECRYPTION ---

		  $ciphertext_dec = base64_decode($ciphertext_base64);

		  # retrieves the IV, iv_size should be created using mcrypt_get_iv_size()
		  $iv_dec = substr($ciphertext_dec, 0, $iv_size);

		  # retrieves the cipher text (everything except the $iv_size in the front)
		  $ciphertext_dec = substr($ciphertext_dec, $iv_size);

		  # may remove 00h valued characters from end of plain text
		  $plaintext_dec = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key,
						  $ciphertext_dec, MCRYPT_MODE_CBC, $iv_dec);

		  echo	$plaintext_dec . "
";
	      ?>

	      The above example will output:

	      Key size: 32
	      ENJW8mS2KaJoNB5E5CoSAAu0xARgsR1bdzFWpEn+poYw45q+73az5kYi4j+0haevext1dGrcW8Qi59txfCBV8BBj3bzRP3dFCp3CPQSJ8eU=
	      This string was AES-256 / CBC / ZeroBytePadding encrypted.

	See also mcrypt_module_open(3) for a more advanced API and an example.

PHP Documentation Group 													 MCRYPT_ENCRYPT(3)