Defuse\Crypto\Encoding::loadBytesFromChecksummedAsciiSafeString PHP Метод

    public static function loadBytesFromChecksummedAsciiSafeString($expected_header, $string)
    {
        // Headers must be a constant length to prevent one type's header from
        // being a prefix of another type's header, leading to ambiguity.
        if (Core::ourStrlen($expected_header) !== self::SERIALIZE_HEADER_BYTES) {
            throw new Ex\EnvironmentIsBrokenException('Header must be 4 bytes.');
        }
        $bytes = Encoding::hexToBin($string);
        /* Make sure we have enough bytes to get the version header and checksum. */
        if (Core::ourStrlen($bytes) < self::SERIALIZE_HEADER_BYTES + self::CHECKSUM_BYTE_SIZE) {
            throw new Ex\BadFormatException('Encoded data is shorter than expected.');
        }
        /* Grab the version header. */
        $actual_header = Core::ourSubstr($bytes, 0, self::SERIALIZE_HEADER_BYTES);
        if ($actual_header !== $expected_header) {
            throw new Ex\BadFormatException('Invalid header.');
        }
        /* Grab the bytes that are part of the checksum. */
        $checked_bytes = Core::ourSubstr($bytes, 0, Core::ourStrlen($bytes) - self::CHECKSUM_BYTE_SIZE);
        /* Grab the included checksum. */
        $checksum_a = Core::ourSubstr($bytes, Core::ourStrlen($bytes) - self::CHECKSUM_BYTE_SIZE, self::CHECKSUM_BYTE_SIZE);
        /* Re-compute the checksum. */
        $checksum_b = \hash(self::CHECKSUM_HASH_ALGO, $checked_bytes, true);
        /* Check if the checksum matches. */
        if (!Core::hashEquals($checksum_a, $checksum_b)) {
            throw new Ex\BadFormatException("Data is corrupted, the checksum doesn't match");
        }
        return Core::ourSubstr($bytes, self::SERIALIZE_HEADER_BYTES, Core::ourStrlen($bytes) - self::SERIALIZE_HEADER_BYTES - self::CHECKSUM_BYTE_SIZE);
    }

 /**
  * @expectedException \Defuse\Crypto\Exception\BadFormatException
  * @expectedExceptionMessage not a hex string
  */
 public function testBadHexEncoding()
 {
     $header = Core::secureRandom(Core::HEADER_VERSION_SIZE);
     $str = Encoding::saveBytesToChecksummedAsciiSafeString($header, Core::secureRandom(Core::KEY_BYTE_SIZE));
     $str[0] = 'Z';
     Encoding::loadBytesFromChecksummedAsciiSafeString($header, $str);
 }