Summery Summery
AEAD Decryption with ChaCha20-Poly1305, IETF mode (96-bit nonce)
Syntax Syntax
Parameters Parameters
- $message
-
(Optional)
Default value: ''
- $ad
-
(Optional)
Default value: ''
- $nonce
-
(Optional)
Default value: ''
- $key
-
(Optional)
Default value: ''
Return Return
(string)
Source Source
File: wp-includes/sodium_compat/src/Crypto32.php
public static function aead_chacha20poly1305_ietf_decrypt( $message = '', $ad = '', $nonce = '', $key = '' ) { /** @var int $adlen - Length of associated data */ $adlen = ParagonIE_Sodium_Core32_Util::strlen($ad); /** @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_IETF_ABYTES; /** @var string The first block of the chacha20 keystream, used as a poly1305 key */ $block0 = ParagonIE_Sodium_Core32_ChaCha20::ietfStream( 32, $nonce, $key ); /** @var string $mac - Message authentication code */ $mac = ParagonIE_Sodium_Core32_Util::substr( $message, $len - self::aead_chacha20poly1305_IETF_ABYTES, self::aead_chacha20poly1305_IETF_ABYTES ); /** @var string $ciphertext - The encrypted message (sans MAC) */ $ciphertext = ParagonIE_Sodium_Core32_Util::substr( $message, 0, $len - self::aead_chacha20poly1305_IETF_ABYTES ); /* 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(str_repeat("\x00", ((0x10 - $adlen) & 0xf))); $state->update($ciphertext); $state->update(str_repeat("\x00", (0x10 - $clen) & 0xf)); $state->update(ParagonIE_Sodium_Core32_Util::store64_le($adlen)); $state->update(ParagonIE_Sodium_Core32_Util::store64_le($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::ietfStreamXorIc( $ciphertext, $nonce, $key, ParagonIE_Sodium_Core32_Util::store64_le(1) ); }