{

            byte[] keyArray;

            byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);

            System.Configuration.AppSettingsReader settingsReader = new AppSettingsReader();

            string key = (string)settingsReader.GetValue("SecurityKey", typeof(String));

            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();

            keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));

            hashmd5.Clear();

            TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();

            tdes.Key = keyArray;

            tdes.Mode = CipherMode.ECB;

            tdes.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdes.CreateEncryptor();

            byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

            tdes.Clear();

            return Convert.ToBase64String(resultArray);

        }

        {

            byte[] keyArray;

            byte[] toEncryptArray = Convert.FromBase64String(toDecrypt);

            System.Configuration.AppSettingsReader settingsReader = new AppSettingsReader();

            string key = (string)settingsReader.GetValue("SecurityKey", typeof(String));

            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();

            keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));

            hashmd5.Clear();

            TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();

            tdes.Key = keyArray;

            tdes.Mode = CipherMode.ECB;

            tdes.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdes.CreateDecryptor();

            byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

            tdes.Clear();

            return UTF8Encoding.UTF8.GetString(resultArray);

        }

<appSettings>

    <add key="SecurityKey" value="mohan"/>

 

  </appSettings>