mcrypt_decrypt(3) [php man page]

MCRYPT_DECRYPT(3)							 1							 MCRYPT_DECRYPT(3)

mcrypt_decrypt - Decrypts crypttext with given parameters

SYNOPSIS

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

DESCRIPTION

	Decrypts the $data and returns the unencrypted data.

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 was encrypted. If the provided key size is not supported by the cipher, the function will emit a
		warning and return FALSE

	      o $data
		- The data that will be decrypted with the given $cipher and $mode. If the size of the data is not n * blocksize, the data will be
		padded with ' '.

	      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 the provided IV size is not sup-
		ported by the chaining mode or no IV was provided, but the chaining mode requires one, the function will emit a warning and return
		FALSE.

RETURN VALUES

	Returns the decrypted data as a string or FALSE on failure.

CHANGELOG

       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 5.6.0	|						    |
       |	|						    |
       |	|  Invalid   $key  and	$iv  sizes  are  no  longer |
       |	| accepted.  mcrypt_decrypt(3)	will  now  throw  a |
       |	| warning  and	return	FALSE  if  the	inputs	are |
       |	| invalid. Previously keys and IVs were padded with |
       |	| ' ' bytes to the next valid size.		    |
       |	|						    |
       +--------+---------------------------------------------------+
SEE ALSO

       mcrypt_encrypt(3).

PHP Documentation Group 													 MCRYPT_DECRYPT(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)