带密钥的sha1加密：
private static string HmacSha1Sign(string jsonStr, string secretKey, string enCoding )
{
Encoding encoding = Encoding.GetEncoding(enCoding);
string encodedParam = Convert.ToBase64String(encoding.GetBytes(jsonStr));
byte[] bytes = encoding.GetBytes(jsonStr);
HMACSHA1 transform = new HMACSHA1(encoding.GetBytes(secretKey));
CryptoStream stream = new CryptoStream(Stream.Null, transform, CryptoStreamMode.Write);
stream.Write(bytes, , bytes.Length);
stream.Close();
return Convert.ToBase64String(transform.Hash);
}