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client-server application encrypt/decrypt

Posted on 2014-12-26
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Last Modified: 2015-01-03
Hi,

I have client server application, I am trying to encrypt all data communication between client and server. Please suggest me how can i do it? Should I use System.Security.Cryptography class or there is any easy way too.

Please guide,

Thanks
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Question by:Bertrand Russell
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LVL 32

Expert Comment

by:Stefan Hoffmann
ID: 40518403
Well, it depends on your concrete type of communications and the concrete requirements.

Do you need protocol or message encryption? The first could be done by tunneling, e.g. SSL/SSH. So this can be done by the OS.
Message encryption means that you application needs to handled by you application.

So without further information, it's hard to guess.
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Author Comment

by:Bertrand Russell
ID: 40518433
thanks for message. I need message level encryption
Please guide

Thanks
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LVL 32

Expert Comment

by:Stefan Hoffmann
ID: 40518454
What kind of communications? Web Services (WCF) has already a built-in mechanism for that:

E.g.

<bindings>
	<wsHttpBinding>
		<binding name="netTcpEndpointBinding">
			<security mode="message"></security>
		</binding>
	</wsHttpBinding>
</bindings>

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See also:

* Message Security in WCF
* Chapter 7: Message and Transport Security
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Author Comment

by:Bertrand Russell
ID: 40518485
It is windows service, so client is c# interface/application and server is a windows service. Please guide how to make message level encryption! thx
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LVL 32

Expert Comment

by:Stefan Hoffmann
ID: 40518535
In this general case you need to encrypt/decrypt each message. Here you use the System.Security.Cryptography namspace of the .Net framework.

See Encrypting and Decrypting Data.
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Author Comment

by:Bertrand Russell
ID: 40518565
I have tried this code, it is encrypting and decrypting data well on local machine but when I send data to remote machine, the decryption fails. What is wrong in this code that make it not working on remote machine while working on local is fine!

  public static byte[] Key = new byte[]{0x43, 0x72, 0x6e, 0x6d, 0x54, 0x4d, 0x65,
                                      0x94, 0x16, 0x32, 0x44, 0x84, 0x7e, 0x18,
                                      0x64, 0x76, 0x6e, 0x63, 0x64, 0x7a, 0x5f,
                                      0x84, 0x7f, 0x9a};

        public static string Encrypt(string toEncrypt, bool useHashing)
        {
            byte[] keyArray;
            byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);


            if (useHashing)
            {
                MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                //keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                keyArray = hashmd5.ComputeHash(Key);

                hashmd5.Clear();
            }
            else
                keyArray = Key;

            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);
            //Release resources held by TripleDes Encryptor
            tdes.Clear();
            //Return the encrypted data into unreadable string format
            return Convert.ToBase64String(resultArray, 0, resultArray.Length);
        }

        public static string Decrypt(string cipherString, bool useHashing)
        {
            byte[] keyArray;
            //get the byte code of the string

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



            if (useHashing)
            {
                //if hashing was used get the hash code with regards to your key
                MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                //keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                keyArray = hashmd5.ComputeHash(Key);
                //release any resource held by the MD5CryptoServiceProvider

                hashmd5.Clear();
            }
            else
            {
                keyArray = Key;
            }

            TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
            //set the secret key for the tripleDES algorithm
            tdes.Key = keyArray;

            tdes.Mode = CipherMode.ECB;
            //padding mode(if any extra byte added)
            tdes.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdes.CreateDecryptor();
            byte[] resultArray = cTransform.TransformFinalBlock(
                                 toEncryptArray, 0, toEncryptArray.Length);
            //Release resources held by TripleDes Encryptor                
            tdes.Clear();
            //return the Clear decrypted TEXT
            return UTF8Encoding.UTF8.GetString(resultArray);
        }

        public static Byte[] Encrypt(Byte[] toEncrypt, bool useHashing)
        {
            byte[] keyArray;
            // byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);
            byte[] toEncryptArray = toEncrypt;

            if (useHashing)
            {
                MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                //keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                keyArray = hashmd5.ComputeHash(Key);

                hashmd5.Clear();
            }
            else
                keyArray = Key;

            TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
            //set the secret key for the tripleDES algorithm
            tdes.Key = keyArray;
            //mode of operation. there are other 4 modes.
            //We choose ECB(Electronic code Book)
            tdes.Mode = CipherMode.ECB;
            //padding mode(if any extra byte added)

            tdes.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdes.CreateEncryptor();
            //transform the specified region of bytes array to resultArray
            byte[] resultArray =
              cTransform.TransformFinalBlock(toEncryptArray, 0,
              toEncryptArray.Length);
            //Release resources held by TripleDes Encryptor
            tdes.Clear();
            //Return the encrypted data into unreadable string format
            // return Convert.ToBase64String(resultArray, 0, resultArray.Length);
            return resultArray;
        }

        public static Byte[] Decrypt(Byte[] cipherString, bool useHashing)
        {
            byte[] keyArray;
            //get the byte code of the string

            // byte[] toEncryptArray = Convert.FromBase64String(cipherString);
            byte[] toEncryptArray = cipherString;



            if (useHashing)
            {
                //if hashing was used get the hash code with regards to your key
                MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                //keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                keyArray = hashmd5.ComputeHash(Key);
                //release any resource held by the MD5CryptoServiceProvider

                hashmd5.Clear();
            }
            else
            {
                //if hashing was not implemented get the byte code of the key
                //keyArray = UTF8Encoding.UTF8.GetBytes(key);
                keyArray = Key;
            }

            TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
            //set the secret key for the tripleDES algorithm
            tdes.Key = keyArray;
            //mode of operation. there are other 4 modes. 
            //We choose ECB(Electronic code Book)

            tdes.Mode = CipherMode.ECB;
            //padding mode(if any extra byte added)
            tdes.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdes.CreateDecryptor();
            byte[] resultArray = cTransform.TransformFinalBlock(
                                 toEncryptArray, 0, toEncryptArray.Length);
            //Release resources held by TripleDes Encryptor                
            tdes.Clear();
            //return the Clear decrypted TEXT
            // return UTF8Encoding.UTF8.GetString(resultArray);
            return resultArray;
        }

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Accepted Solution

by:
mkk3939 earned 500 total points
ID: 40529576
key on both sides should be same, otherwise it can make problem. Otherwise, code is fine, I checked it at my end.
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Author Closing Comment

by:Bertrand Russell
ID: 40529577
Yes, thanks
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