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sodium_crypto_secretbox_open

PHP function Edit on GitHub ✎

(PHP 7 >= 7.2.0, PHP 8)

Authenticated shared-key decryption

Description

sodium_crypto_secretbox_open(string $ciphertext, string $nonce, string $key): string|false

Decrypt an encrypted message with a symmetric (shared) key.

Parameters

ciphertext: Must be in the format provided by sodium_crypto_secretbox() (ciphertext and tag, concatenated).
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

The decrypted string on successFalseforfailure.

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.

Examples

sodium_crypto_secretbox_open() example

php

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

// The same nonce and key are required to decrypt the $ciphertext
$plaintext = sodium_crypto_secretbox_open($ciphertext, $nonce, $key);
if ($plaintext !== false) {
    echo $plaintext . PHP_EOL;
}
?>

The above example will output:

output

message to be encrypted