在文件尾添加16字节的MD5校验码用于网络或其它方式的发布，接收方收到文件后进行MD5验证，验证通过证明文件完整无误地接收-The end of the file, add the 16-byte MD5 checksum for the release of the network or otherwise, the recipient receives the file MD5 authentication to verify documents is complete and correc