sodium_crypto_secretbox

(PHP 7 >= 7.2.0, PHP 8)

sodium_crypto_secretbox — Authenticated shared-key encryption

Description

sodium_crypto_secretbox(string$message, string$nonce, string$key): string

Encrypt a message with a symmetric (shared) key.

Parameters

message: The plaintext message to encrypt.
nonce: A number that must be only used once, per message. 24 bytes long. This is a large enough bound to generate randomly (i.e. random_bytes()).
key: Encryption key (256-bit).

Return Values

Returns the encrypted string.

Errors/Exceptions

If nonce has a length of bytes different than SODIUM_CRYPTO_SECRETBOX_NONCEBYTES (24 bytes), a SodiumException will be thrown.
If key has a length of bytes different than SODIUM_CRYPTO_SECRETBOX_KEYBYTES (32 bytes), a SodiumException will be thrown.
Throws a SodiumException on failure.

Examples

Example #1 sodium_crypto_secretbox() example

<?php
// The $key must be kept confidential
$key = sodium_crypto_secretbox_keygen();
// Do not reuse $nonce with the same key
$nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
$plaintext = "message to be encrypted";
$ciphertext = sodium_crypto_secretbox($plaintext, $nonce, $key);

var_dump(bin2hex($ciphertext));
// The same nonce and key are required to decrypt the $ciphertext
var_dump(sodium_crypto_secretbox_open($ciphertext, $nonce, $key));
?>

The above example will output something similar to:

string(78) "3a1fa3e9f7b72ef8be51d40abf8e296c6899c185d07b18b4c93e7f26aa776d24c50852cd6b1076" string(23) "message to be encrypted"