用C# 实现标准MD5WithRSA算法

  public class md5withRsa
    {
        public static Encoding encoding = Encoding.GetEncoding("GBK");
        public static string SignerSymbol = "MD5withRSA";

        public  md5withRsa() { }

        public  md5withRsa(Encoding e, string s)
        {
            encoding = e;
            SignerSymbol = s;
        }

        private static AsymmetricKeyParameter CreateKEY(bool isPrivate, string key)
        {
            byte[] keyInfoByte = Convert.FromBase64String(key);

            if (isPrivate)
                return PrivateKeyFactory.CreateKey(keyInfoByte);
            else
                return PublicKeyFactory.CreateKey(keyInfoByte);
        }

        /// <summary>
        /// 数据加密
        /// </summary>
        /// <param name="content">待加密字符串</param>
        /// <param name="privatekey">私钥</param>
        /// <returns>加密后字符串</returns>
        public static string Sign(string content, string privatekey)
        {
            ISigner sig = SignerUtilities.GetSigner(SignerSymbol);

            sig.Init(true, CreateKEY(true, privatekey));

            var bytes = encoding.GetBytes(content);

            sig.BlockUpdate(bytes, 0, bytes.Length);
            byte[] signature = sig.GenerateSignature();
            
            /* Base 64 encode the sig so its 8-bit clean */
            var signedString = Convert.ToBase64String(signature);

            return signedString;
        }

        /// <summary>
        /// 验证签名
        /// </summary>
        /// <param name="content">待签名的字符串</param>
        /// <param name="signData">加密后的文本</param>
        /// <param name="publickey">公钥文本</param>
        /// <returns>是否一致</returns>
        public static bool Verify(string content, string signData, string publickey)
        {
            ISigner signer = SignerUtilities.GetSigner(SignerSymbol);

            signer.Init(false, CreateKEY(false, publickey));

            var expectedSig = Convert.FromBase64String(signData);

            /* Get the bytes to be signed from the string */
            var msgBytes = encoding.GetBytes(content);

            /* Calculate the signature and see if it matches */
            signer.BlockUpdate(msgBytes, 0, msgBytes.Length);
            return signer.VerifySignature(expectedSig);
        }
    }