Encryption is used to transform a data
into some un-readable form so that authenticated person only can read/access
the data. It requires some secret information to transform the plain text to
cipher text; it is usually referred as key.
There are many modern cryptographic methods used for encryption and decryption and
it is classified in to two classes of key based algorithms.
1. Symmetric Algorithm
a. Same key is used for both Encryption and Decryption. The
key will be kept as secret.
b. Symmetric Ciphers is divided into Stream and Block
Ciphers.
i. Stream Ciphers – It encrypts a single bit of plain text at a
time.
ii. Block Ciphers – It takes number of bits
and encrypts them as a single unit.
2. Asymmetric Algorithm
a. Different key is used for Encryption and Decryption. It is also
called as public Key algorithm.
b. Encryption key is public and the Decryption key will be kept as
secret.
c. By using this asymmetric algorithm, anyone can encrypt the
message by using encryption key but the message can be decrypted only by using
decryption key.
3. Hybrid Encryption – Symmetric and
Asymmetric algorithm are used together and it is called as Hybrid Encryption.
Algorithm Requirements:
1. The Key will be kept secret and should be Random.
2. It should not be possible to find the key even if the plain text
and Cipher text are known.
Types of Symmetric
Encryption Algorithm:
1. Data Encryption Standard (DES)
2. Blow Fish
3. Triple DES (3DES)
4. Advanced Encryption Standard (AES)
Below is the example for encryption and decryption
in C# using Triple DES algorithm.
Public class Program
{
static void Main(string[] args)
{
var text = "This is Plain Text";
var encryptedText = CryptoGraphyExample.EncryptPlainTextToCipherText(text);
var decryptedText = CryptoGraphyExample.DecryptCipherTextToPlainText(encryptedText);
Console.WriteLine("Passed Text = " +
text);
Console.WriteLine("EncryptedText = " +
encryptedText);
Console.WriteLine("DecryptedText = " +
decryptedText);
Console.ReadLine();
}
}
public class CryptoGraphyExample
{
/// <summary>
/// This security key
should be very complex and Random for encrypting the text. This playing vital
role in encrypting the text.
/// </summary>
private const string _securityKey = "MyComplexKey";
/// <summary>
/// This method is
used to convert the plain text to Encrypted/Un-Readable Text format.
/// </summary>
/// <param name="PlainText">Plain Text to Encrypt before transferring over the network.</param>
/// <returns>Cipher Text</returns>
public static string EncryptPlainTextToCipherText(string PlainText)
{
//Getting the bytes of Input String.
byte[] toEncryptedArray = UTF8Encoding.UTF8.GetBytes(PlainText);
MD5CryptoServiceProvider objMD5CryptoService
= new MD5CryptoServiceProvider();
//Gettting the bytes from the Security Key and Passing it to
compute the Corresponding Hash Value.
byte[] securityKeyArray =
objMD5CryptoService.ComputeHash(UTF8Encoding.UTF8.GetBytes(_securityKey));
//De-allocatinng the memory after doing the Job.
objMD5CryptoService.Clear();
var objTripleDESCryptoService
= new TripleDESCryptoServiceProvider();
//Assigning the Security key to the TripleDES Service Provider.
objTripleDESCryptoService.Key
= securityKeyArray;
//Mode of the Crypto service is Electronic Code Book.
objTripleDESCryptoService.Mode
= CipherMode.ECB;
//Padding Mode is PKCS7 if there is any extra byte is added.
objTripleDESCryptoService.Padding
= PaddingMode.PKCS7;
var objCrytpoTransform =
objTripleDESCryptoService.CreateEncryptor();
//Transform the bytes array to resultArray
byte[] resultArray = objCrytpoTransform.TransformFinalBlock(toEncryptedArray,
0, toEncryptedArray.Length);
//Releasing the Memory Occupied by TripleDES Service Provider for
Encryption.
objTripleDESCryptoService.Clear();
//Convert and return the encrypted data/byte into string format.
return Convert.ToBase64String(resultArray,
0, resultArray.Length);
}
/// <summary>
/// This method is
used to convert the Cipher/Encypted text to Plain Text.
/// </summary>
/// <param name="CipherText">Encrypted Text</param>
/// <returns>Plain/Decrypted
Text</returns>
public static string DecryptCipherTextToPlainText(string CipherText)
{
byte[] toEncryptArray = Convert.FromBase64String(CipherText);
MD5CryptoServiceProvider objMD5CryptoService
= new MD5CryptoServiceProvider();
//Gettting the bytes from the Security Key and Passing it to
compute the Corresponding Hash Value.
byte[] securityKeyArray =
objMD5CryptoService.ComputeHash(UTF8Encoding.UTF8.GetBytes(_securityKey));
//De-allocatinng the memory after doing the Job.
objMD5CryptoService.Clear();
var objTripleDESCryptoService
= new TripleDESCryptoServiceProvider();
//Assigning the Security key to the TripleDES Service Provider.
objTripleDESCryptoService.Key
= securityKeyArray;
//Mode of the Crypto service is Electronic Code Book.
objTripleDESCryptoService.Mode
= CipherMode.ECB;
//Padding Mode is PKCS7 if there is any extra byte is added.
objTripleDESCryptoService.Padding
= PaddingMode.PKCS7;
var objCrytpoTransform
= objTripleDESCryptoService.CreateDecryptor();
//Transform the bytes array to resultArray
byte[] resultArray = objCrytpoTransform.TransformFinalBlock(toEncryptArray,
0, toEncryptArray.Length);
//Releasing the Memory Occupied by TripleDES Service Provider for
Decryption.
objTripleDESCryptoService.Clear();
//Convert and return the decrypted data/byte into string format.
return UTF8Encoding.UTF8.GetString(resultArray);
}
}
