Cryptography: Symmetric Encryption by Symmetric Algorithm Classes – Part 2

RaviRanjanKr

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19 Aug 2012CPOL5 min read

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This blog enables you to understand the basics of Cryptography with Symmetric Encryption Algorithm Classes.

In the previous blog – [Cryptography : Symmetric Encryption by Symmetric Algorithm Classes – Part 1], we have learned about basic introduction of Cryptography, Symmetric Encryption, Symmetric Encryption Algorithm classes and codes for implementing DES class.

So, now, in addition to the previous blog, here we will learn about TripleDES class, RC2 class and Rijndael class.

TripleDES Class

The TripleDES class is an abstract class that extends the SymmetricAlgorithm class and provides support for the Triple Data Encryption Standard (Triple DES or TDES or TDEA) algorithm. TripleDES is a method kind of using DES (Data Encryption Standard) to provide additional security. TripleDES can be done by using two or three keys.

TripleDES as its name implies increases encryption strength by applying the DES encryption algorithm to data three times before rendering to a result. Since the algorithm performs an encrypt-decrypt-encrypt sequence, this is sometimes called the EDE (Encryption Decryption Encryption) mode. TripleDES algorithm supports an encryption key up to 168 bits (3*156) in size to 192 bits (Triple DES utilizes three 64-bit keys, 64*3 bits) in increments of 64 bits. Triple DES gives a relatively simple and awesome method of increasing the key size of DES (Data Encryption Standard) to protect against attacks.

The following code sample will guide you how to use and implement the TripleDESCryptoServiceProvider class.

Note: SourceCode was almost the same as we have read in the previous article. Just implantation is different so keep focus on the implementation code.

To perform Encryption and Decryption, you must add:

using System.Security.Cryptography; // Namespace

Now take a look at the encryption function:

public static byte[] Encrypt(string strText, SymmetricAlgorithm key)
{
// Create a memory stream.
MemoryStream ms = new MemoryStream();
// Create a CryptoStream using the memory stream and the
// CSP(cryptoserviceprovider) DES key.
CryptoStream crypstream = new CryptoStream(ms, key.CreateEncryptor(), CryptoStreamMode.Write);
// Create a StreamWriter to write a string to the stream.
StreamWriter sw = new StreamWriter(crypstream);
// Write the strText to the stream.
sw.WriteLine(strText);
// Close the StreamWriter and CryptoStream.
sw.Close();
crypstream.Close();
// Get an array of bytes that represents the memory stream.
byte[] buffer = ms.ToArray();
// Close the memory stream.
ms.Close();

// Return the encrypted byte array.
return buffer;
}

In the above code, CreateEncryptor() function is used to encrypt object with the current Key property and initialization vector.

Now in the same way, we need to create function for Decrypt the PlainText (Encrypted Text). Have a look at the given function which is responsible to decrypt encrypted text.

public static string Decrypt(byte[] encryptText, SymmetricAlgorithm key)
        {
            // Create a memory stream to the passed buffer.
            MemoryStream ms = new MemoryStream(encryptText);
            // Create a CryptoStream using  memory stream and CSP DES key.
            CryptoStream crypstream = new CryptoStream(ms, key.CreateDecryptor(), CryptoStreamMode.Read);
            // Create a StreamReader for reading the stream.
            StreamReader sr = new StreamReader(crypstream);
            // Read the stream as a string.
            string val = sr.ReadLine();
            // Close the streams.
            sr.Close();
            crypstream.Close();
            ms.Close();
          return val;
        }

In the above code, decryption is handled in the same way by using CreateDecryptor() function instead of CreateEncryptor().

Now we have created function, so we can use both functions to appropriate manner to accomplishment of Encryption Decryption task.

Note: We need to access TripleDESCryptoServiceProvider class here.

TripleDESCryptoServiceProvider key = new TripleDESCryptoServiceProvider(); // Key is the object

How to Use Encrypt Function

//Creating object of TripleDES class.
TripleDESCryptoServiceProvider key = new TripleDESCryptoServiceProvider();
// Encrypt a string to a byte array.
 byte[] buffer = Encrypt("ABC", key); // ABC is an example you can put anytext as your need

How to Use Decrypt Function

//Creating object of TripleDES class.
TripleDESCryptoServiceProvider key = new TripleDESCryptoServiceProvider();
// You can make global variable for holding encrypted byte array value.
byte[] buffer = Encrypt("ABC", key);
string strText = Decrypt(buffer, key); // strText will hold the original text back.

RC2 Class

The RC2 class is an abstract class that extends the Symmetric Algorithm class and provides support for the RC2 algorithm.

Ron Rivest is the one who discovered RC2, RC4, RC5, and RC6. Hence RC stands for Ron’s Codes. However, Lotus Software Company is the backend in creating the whole script of RC2 algorithm.

Reference Link: http://en.wikipedia.org/wiki/RC2

The RC2CryptoServiceProvider object is a block cipher that encrypts and decrypts data in blocks of 8 bytes. This class pads the final block of data if it is less than 8 bytes. As a result of this padding, the length of encrypted data could be greater than the original plaintext.

The RC2 class provides the EffectiveKeySize property, which is used to get or set the effective key size of the RC2 secret encryption key. An exception occurs whenever size is detected. The RC2CryptoServiceProvider class is the concrete RC2 algorithm class and it extends the RC2 class. The RC2CryptoServiceProvider class provides the UseSalt property. The UseSalt proeperty is set to false by default. However, in any condition if this(usesalt) property is set to True, the encrypted value includes an 11-byte long 0 value salt.

Note: We need to access RC2CryptoServiceProvider class here.

RC2CryptoServiceProvider key = new RC2CryptoServiceProvider();

The same Function of Encryption and Decryption which we used in previous Symmetric Encryption program. Just point to be noted to change the Symmetric class here which is RC2CryptoServiceProvider for RC2 encryption.

How to Use Encrypt Function

//Creating object of RC2 class.
RC2CryptoServiceProvider key = new RC2CryptoServiceProvider();
// Encrypt a string to a byte array.
 byte[] buffer = Encrypt("ABC", key); // ABC is an example you can put anytext as your need

How to Use Decrypt Function

//Creating object of RC2 class.
RC2CryptoServiceProvider key = new RC2CryptoServiceProvider();
// You can make global variable for holding encrypted byte array value.
byte[] buffer = Encrypt("ABC", key);
string strText = Decrypt(buffer, key); // strText will hold the original text back.

Rijndael Class

The Rijndael class is an abstract class that extends the SymmetricAlgorithm class and provides support for the Rijndael algorithm. The algorithm of Rijndael encryption has been designed to replace the aging DES (Data Encryption Standard) algorithm. Like DES, it is a block cipher. It uses 128-bit, 192-bit or 256-bit keys. This implementation encrypts 128-bit blocks. (DES used 56-bit keys and 64-bit blocks.)

As we have read, it is considered to be the replacement for the DES algorithm and was adopted as a Federal Information Processing Standard(FIPS) standard in 2001. The RijndaelManaged class is a concrete class and it extends the Rijndael class. The Rijndael class is extended by CLR managed class, whereas the Symmetric encryption classes are extended by CSPs. The RijndaelManagedTransform class is initialized by the CreateEncryptor and CreateDecryptor methods of the RijndaelManaged class and is used in conjuction with the RijndaelMaaged class to encrypt data.

In .NET Framework, Rijndael algorithm supports a fixed encryption key size of 128 bits, 192 bits, 192 bits or 256 bits as 9 rounds if the key/block size is 128 bits, 11 rounds if the key/block size is 192 bits and 13 rounds if the key/block size is 256 bits.
The Rijndael class is the predecessor of the Aes algorithm. You should use the Aes algorithm instead of Rijndael.

Note: We need to access RijndaelManaged class here.

RijndaelManaged key = new RijndaelManaged();

The same Function of Encryption and Decryption which we used in previous Symmetric Encryption program. Just point to be noted to change the Symmetric class here which is RijndaelManaged for Rijndael encryption.

How to Use Encrypt Function

//Creating object of RijndaelManaged class.
RijndaelManaged key = new RijndaelManaged();
// Encrypt a string to a byte array.
 byte[] buffer = Encrypt("ABC", key); // ABC is an example you can put anytext as your need

How to Use Decrypt Function

//Creating object of RijndaelManaged class.
RijndaelManaged key = new RijndaelManaged();
// You can make global variable for holding encrypted byte array value.
byte[] buffer = Encrypt("ABC", key);
string strText = Decrypt(buffer, key); // strText will hold the original text back.

Look at the below diagrams for output by using different Symmetric Algorithm applied on same plain text (e.g.: ABC)