使用MD5WithRSA來簽名和驗簽（.NET）

        /// <summary>
        /// 數字簽名並返回BASE64編碼的字符串
        /// </summary>
        /// <param name="contentForSign">待簽名內容</param>
        /// <param name="privateKeyFile">私鑰文件路徑</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>
        /// 驗證簽名
        /// </summary>
        /// <param name="contentForSign">待簽名內容</param>
        /// <param name="signedData">簽名內容</param>
        /// <param name="publicKeyFile">公鑰文件路徑</param>
        /// <returns>驗證結果</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));
        }