ParagonIE_Sodium_Crypto32::aead_chacha20poly1305_decrypt() public WP 1.0
AEAD Decryption with ChaCha20-Poly1305
{} It's a method of the class: ParagonIE_Sodium_Crypto32{}
No Hooks.
Return
String
. Null. Nothing.
Usage
$result = ParagonIE_Sodium_Crypto32::aead_chacha20poly1305_decrypt(;
Code of ParagonIE_Sodium_Crypto32::aead_chacha20poly1305_decrypt() ParagonIE Sodium Crypto32::aead chacha20poly1305 decrypt WP 5.7
public static function aead_chacha20poly1305_decrypt(
$message = '',
$ad = '',
$nonce = '',
$key = ''
) {
/** @var int $len - Length of message (ciphertext + MAC) */
$len = ParagonIE_Sodium_Core32_Util::strlen($message);
/** @var int $clen - Length of ciphertext */
$clen = $len - self::aead_chacha20poly1305_ABYTES;
/** @var int $adlen - Length of associated data */
$adlen = ParagonIE_Sodium_Core32_Util::strlen($ad);
/** @var string $mac - Message authentication code */
$mac = ParagonIE_Sodium_Core32_Util::substr(
$message,
$clen,
self::aead_chacha20poly1305_ABYTES
);
/** @var string $ciphertext - The encrypted message (sans MAC) */
$ciphertext = ParagonIE_Sodium_Core32_Util::substr($message, 0, $clen);
/** @var string The first block of the chacha20 keystream, used as a poly1305 key */
$block0 = ParagonIE_Sodium_Core32_ChaCha20::stream(
32,
$nonce,
$key
);
/* Recalculate the Poly1305 authentication tag (MAC): */
$state = new ParagonIE_Sodium_Core32_Poly1305_State($block0);
try {
ParagonIE_Sodium_Compat::memzero($block0);
} catch (SodiumException $ex) {
$block0 = null;
}
$state->update($ad);
$state->update(ParagonIE_Sodium_Core32_Util::store64_le($adlen));
$state->update($ciphertext);
$state->update(ParagonIE_Sodium_Core32_Util::store64_le($clen));
$computed_mac = $state->finish();
/* Compare the given MAC with the recalculated MAC: */
if (!ParagonIE_Sodium_Core32_Util::verify_16($computed_mac, $mac)) {
throw new SodiumException('Invalid MAC');
}
// Here, we know that the MAC is valid, so we decrypt and return the plaintext
return ParagonIE_Sodium_Core32_ChaCha20::streamXorIc(
$ciphertext,
$nonce,
$key,
ParagonIE_Sodium_Core32_Util::store64_le(1)
);
}