使用MD5WithRSA来签名和验签（.NET）

        /// <summary>
        /// 数字签名并返回BASE64编码的字符串
        /// </summary>
        /// <param name="contentForSign">待签名内容</param>
        /// <param name="privateKeyFile">私钥文件路径</param>
        /// <returns></returns>
        internal static string Sign(string contentForSign, string privateKeyFile)
        {
            var rsa = CcbRsaCryptProvider.GetInstanceForSign(privateKeyFile);
            var signData = rsa.SignData(Encoding.UTF8.GetBytes(contentForSign), new MD5CryptoServiceProvider());
            return Convert.ToBase64String(signData);
        }

        /// <summary>
        /// 验证签名
        /// </summary>
        /// <param name="contentForSign">待签名内容</param>
        /// <param name="signedData">签名内容</param>
        /// <param name="publicKeyFile">公钥文件路径</param>
        /// <returns>验证结果</returns>
        internal static bool VerifySign(string contentForSign, string signedData, string publicKeyFile)
        {
            var rsaPub = CcbRsaCryptProvider.GetInstanceForVerifySign(publicKeyFile);
            return rsaPub.VerifyData(Encoding.UTF8.GetBytes(contentForSign), new MD5CryptoServiceProvider(), Convert.FromBase64String(signedData));
        }