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Mcrypt Functions
PHP Manual

# mcrypt_encrypt

Encrypts plaintext with given parameters

### Description

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

Encrypts the data and returns it.

### Parameters

`cipher`

  One of the `MCRYPT_ciphername` constants, or the name of the algorithm as string.

`key`

  The key with which the data will be encrypted. If it's smaller than the required keysize, it is padded with '\0'. 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.

`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 '\0'.

  The returned crypttext can be larger than the size of the data that was given by `data`.

`mode`

  One of the `MCRYPT_MODE_modename` constants, or one of the following strings: "ecb", "cbc", "cfb", "ofb", "nofb" or "stream".

`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 "\0".

### Return Values

Returns the encrypted data, as a string.

### Examples

Example #1 mcrypt_encrypt 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 . "\n";
$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 . "\n";
# === 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 . "\n";
?>`

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 for a more advanced API and an example.