sodium_crypto_secretbox_open
(PHP 7 >= 7.2.0, PHP 8)
sodium_crypto_secretbox_open — Authenticated shared-key decryption
Description
sodium_crypto_secretbox_open(string
$ciphertext, string $nonce, string $key): string|falseDecrypt 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 success or false on failure.
Errors/Exceptions
-
If
noncehas a length of bytes different thanSODIUM_CRYPTO_SECRETBOX_NONCEBYTES(24 bytes), a SodiumException will be thrown. -
If
keyhas a length of bytes different thanSODIUM_CRYPTO_SECRETBOX_KEYBYTES(32 bytes), a SodiumException will be thrown.
Examples
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 nouce 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
See Also
- sodium_crypto_secretbox() - Authenticated shared-key encryption
- sodium_crypto_secretbox_keygen() - Generate random key for sodium_crypto_secretbox
- random_bytes() - Generates cryptographically secure pseudo-random bytes
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