(PHP 7 >= 7.2.0, PHP 8)
sodium_crypto_secretbox_open — Authenticated shared-key decryption
$ciphertext, string $nonce, #[\SensitiveParameter] string $key): string|falseDecrypt an encrypted message with a symmetric (shared) key.
ciphertextMust be in the format provided by sodium_crypto_secretbox() (ciphertext and tag, concatenated).
nonceA 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()).
keyEncryption key (256-bit).
The decrypted string on success or false on failure.
nonce has a length of bytes different than
SODIUM_CRYPTO_SECRETBOX_NONCEBYTES
(24 bytes), a SodiumException will be thrown.
key has a length of bytes different than
SODIUM_CRYPTO_SECRETBOX_KEYBYTES
(32 bytes), a SodiumException will be thrown.
Example #1 sodium_crypto_secretbox_open() example
<?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:
message to be encrypted
This method will return a string, or false if the data failed to be decrypted.
$key = 'secret';
$data = 'binarydata';
$nonce = random_bytes(SODIUM_CRYPT_SECRETBOX_NONCEBYTES);
$decrypted = sodium_crypto_secretbox_open($data, $nonce, $key);
if ($decrypted === false) {
throw new Exception('failed to decrypt data');
}