hChaCha20 example

    public static function aead_xchacha20poly1305_ietf_decrypt(
        $message = '',
        $ad = '',
        $nonce = '',
        $key = ''
    ) {
        $subkey = ParagonIE_Sodium_Core_HChaCha20::hChaCha20(
            ParagonIE_Sodium_Core_Util::substr($nonce, 0, 16),
            $key
        );
        $nonceLast = "\x00\x00\x00\x00" .
            ParagonIE_Sodium_Core_Util::substr($nonce, 16, 8);

        return self::aead_chacha20poly1305_ietf_decrypt($message, $ad, $nonceLast, $subkey);
    }

    /** * AEAD Encryption with ChaCha20-Poly1305, IETF mode (96-bit nonce) * * @internal Do not use this directly. Use ParagonIE_Sodium_Compat. * * @param string $message * @param string $ad * @param string $nonce * @param string $key * @return string * @throws SodiumException * @throws TypeError */

    public static function aead_xchacha20poly1305_ietf_decrypt(
        $message = '',
        $ad = '',
        $nonce = '',
        $key = ''
    ) {
        $subkey = ParagonIE_Sodium_Core32_HChaCha20::hChaCha20(
            ParagonIE_Sodium_Core32_Util::substr($nonce, 0, 16),
            $key
        );
        $nonceLast = "\x00\x00\x00\x00" .
            ParagonIE_Sodium_Core32_Util::substr($nonce, 16, 8);

        return self::aead_chacha20poly1305_ietf_decrypt($message, $ad, $nonceLast, $subkey);
    }

    /** * AEAD Encryption with ChaCha20-Poly1305, IETF mode (96-bit nonce) * * @internal Do not use this directly. Use ParagonIE_Sodium_Compat. * * @param string $message * @param string $ad * @param string $nonce * @param string $key * @return string * @throws SodiumException * @throws TypeError */

    public static function stream($len = 64, $nonce = '', $key = '')
    {
        if (self::strlen($nonce) !== 24) {
            throw new SodiumException('Nonce must be 24 bytes long');
        }
        return self::encryptBytes(
            new ParagonIE_Sodium_Core32_ChaCha20_Ctx(
                self::hChaCha20(
                    self::substr($nonce, 0, 16),
                    $key
                ),
                self::substr($nonce, 16, 8)
            ),
            str_repeat("\x00", $len)
        );
    }

    /** * @internal You should not use this directly from another application * * @param string $message * @param string $nonce * @param string $key * @param string $ic * @return string * @throws SodiumException * @throws TypeError */

    public static function stream($len = 64, $nonce = '', $key = '')
    {
        if (self::strlen($nonce) !== 24) {
            throw new SodiumException('Nonce must be 24 bytes long');
        }
        return self::encryptBytes(
            new ParagonIE_Sodium_Core_ChaCha20_Ctx(
                self::hChaCha20(
                    self::substr($nonce, 0, 16),
                    $key
                ),
                self::substr($nonce, 16, 8)
            ),
            str_repeat("\x00", $len)
        );
    }

    /** * @internal You should not use this directly from another application * * @param int $len * @param string $nonce * @param string $key * @return string * @throws SodiumException * @throws TypeError */