public string SHA1_Hash(string str_sha1_in)
        {
            SHA1 sha1 = new SHA1CryptoServiceProvider();
            byte[] bytes_sha1_in = UTF8Encoding.Default.GetBytes(str_sha1_in);
            byte[] bytes_sha1_out = sha1.ComputeHash(bytes_sha1_in);
            string str_sha1_out = BitConverter.ToString(bytes_sha1_out);
            str_sha1_out = str_sha1_out.Replace("-", "").ToLower();
            return str_sha1_out;
        }