Encrypts data

# openssl_encrypt

(PHP 5 >= 5.3.0, PHP 7, PHP 8)

openssl_encrypt — Encrypts data

### Description

openssl_encrypt(
#[\SensitiveParameter] string `$data`,
string `$cipher_algo`,
#[\SensitiveParameter] string `$passphrase`,
int `$options` = 0,
string `$iv` = "",
string `&$tag` = `null`,
string `$aad` = "",
int `$tag_length` = 16
): string|false

Encrypts given data with given method and passphrase, returns a raw or base64 encoded string

### Parameters

`data`

  The plaintext message data to be encrypted.

`cipher_algo`

  The cipher method. For a list of available cipher methods, use openssl_get_cipher_methods().

`passphrase`

  The passphrase. If the passphrase is shorter than expected, it is silently padded with `NUL` characters; if the passphrase is longer than expected, it is silently truncated.

  Caution

  There is no key derivation function used for `passphrase` as its name might suggest. The only operation used is padding with `NUL` characters or truncation if the length is different than expected.

`options`

  `options` is a bitwise disjunction of the flags `OPENSSL_RAW_DATA`, and `OPENSSL_ZERO_PADDING` or `OPENSSL_DONT_ZERO_PAD_KEY`.

`iv`

  A non-`null` Initialization Vector. If the IV is shorter than expected, it is padded with `NUL` characters and warning is emitted; if the passphrase is longer than expected, it is truncated and warning is emitted.

`tag`

  The authentication tag passed by reference when using AEAD cipher mode (GCM or CCM).

`aad`

  Additional authenticated data.

`tag_length`

  The length of the authentication `tag`. Its value can be between 4 and 16 for GCM mode.

### Return Values

Returns the encrypted string on success or `false` on failure.

### Errors/Exceptions

Emits an `E_WARNING` level error if an unknown cipher algorithm is passed in via the `cipher_algo` parameter.

Emits an `E_WARNING` level error if an empty value is passed in via the `iv` parameter.

### Changelog

Version | Description
--- | ---
7.1.0 | The `tag`, `aad` and `tag_length` parameters were added.

### Examples

Example #1 AES Authenticated Encryption in GCM mode example for PHP 7.1+

`<?php
//$key should have been previously generated in a cryptographically safe way, like openssl_random_pseudo_bytes
$plaintext = "message to be encrypted";
$cipher = "aes-128-gcm";
if (in_array($cipher, openssl_get_cipher_methods()))
{
$ivlen = openssl_cipher_iv_length($cipher);
$iv = openssl_random_pseudo_bytes($ivlen);
$ciphertext = openssl_encrypt($plaintext, $cipher, $key, $options=0, $iv, $tag);
//store $cipher, $iv, and $tag for decryption later
$original_plaintext = openssl_decrypt($ciphertext, $cipher, $key, $options=0, $iv, $tag);
echo $original_plaintext."\n";
}
?>`

Example #2 AES Authenticated Encryption example prior to PHP 7.1

`<?php
//$key previously generated safely, ie: openssl_random_pseudo_bytes
$plaintext = "message to be encrypted";
$ivlen = openssl_cipher_iv_length($cipher="AES-128-CBC");
$iv = openssl_random_pseudo_bytes($ivlen);
$ciphertext_raw = openssl_encrypt($plaintext, $cipher, $key, $options=OPENSSL_RAW_DATA, $iv);
$hmac = hash_hmac('sha256', $ciphertext_raw, $key, $as_binary=true);
$ciphertext = base64_encode( $iv.$hmac.$ciphertext_raw );
//decrypt later....
$c = base64_decode($ciphertext);
$ivlen = openssl_cipher_iv_length($cipher="AES-128-CBC");
$iv = substr($c, 0, $ivlen);
$hmac = substr($c, $ivlen, $sha2len=32);
$ciphertext_raw = substr($c, $ivlen+$sha2len);
$original_plaintext = openssl_decrypt($ciphertext_raw, $cipher, $key, $options=OPENSSL_RAW_DATA, $iv);
$calcmac = hash_hmac('sha256', $ciphertext_raw, $key, $as_binary=true);
if (hash_equals($hmac, $calcmac))// timing attack safe comparison
{
echo $original_plaintext."\n";
}
?>`

### See Also

- openssl_decrypt() - Decrypts data

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