加密和解密之非对称加密

 public  class RSACSProviderSecurity
    {
        /// <summary>
        /// 密钥,时间戳
        /// 密钥+时间戳=明文签名
        /// </summary>
        #region 公钥加密方法
        public static string EncryptRSACSPSecurity(string key, string timestamp, string publickey, Encoding encoding = default(Encoding))
        {
             if (string.IsNullOrEmpty(key))  

           {
                throw new ArgumentNullException("key");
            }

             if (string.IsNullOrEmpty(timestamp))
            {
                throw new ArgumentNullException("timestamp");
            }

            encoding = encoding ?? Encoding.UTF8;
            string plainText = string.Format("key={0}&timestamp={1}", key, timestamp);
            byte[] plainData = encoding.GetBytes(plainText);
            byte[] cipherData =Encrypt(plainData,publickey);
            return Convert.ToBase64String(cipherData);

    }
        private static byte[] Encrypt(byte[] plainText, string xmlPublicKey)
        {
            if (plainText == null)
            {
                throw new ArgumentNullException("plainText");
            }

         RSACryptoServiceProvider rsaCryptoServiceProvider = new RSACryptoServiceProvider();
            rsaCryptoServiceProvider.FromXmlString(xmlPublicKey);
            return rsaCryptoServiceProvider.Encrypt(plainText, true);
        }

   #endregion

   #region 私钥解密方法       

  public static bool DecryptRSACSPSecurity(string key, string timestamp, string base64Signature, string privateKey, Encoding encoding = default(Encoding))        

{

        if (string.IsNullOrEmpty(key))
            {
                return false;
            }
            if (string.IsNullOrEmpty(timestamp))
            {
                return false;
            }
            if (string.IsNullOrEmpty(base64Signature))
            {
                return false;
            }
            encoding = encoding ?? Encoding.UTF8;
            byte[] cipherData = Convert.FromBase64String(base64Signature);
            byte[] plainData = Decrypt(cipherData,privateKey);
            string plainSignature = encoding.GetString(plainData);
            string signature = string.Format("key={0}&timestamp={1}", key, timestamp);
            return plainSignature == signature;
        }

       private static byte[] Decrypt(byte[] cipherText, string xmlPrivateKey)
        {
            if (cipherText == null)
            {
                throw new ArgumentNullException("cipherText");
            }
            RSACryptoServiceProvider rsaCryptoServiceProvider = new RSACryptoServiceProvider();
            rsaCryptoServiceProvider.FromXmlString(xmlPrivateKey);
            return rsaCryptoServiceProvider.Decrypt(cipherText, true);
        }

}

 #region  生成公钥或者私钥
    //RSACryptoServiceProvider oRSA = new RSACryptoServiceProvider();
    //string privatekey = oRSA.ToXmlString(true);//私钥
    //string publickey = oRSA.ToXmlString(false);//公钥
    #endregion