Encrypt and Decrypt a String

• Download source files - 12.73 KB
• Download demo project - 8.58 KB

Introduction

If you write a secure program, you should secure something such as a password, private key and something else…
For this propose, this article can help you to encrypt a string and decrypt a string by using some method.

Background

This article explains 4 method to encrypt a string in .NET 2.0. There are 4 popular methods to encrypt a string:

1. DES
2. RC2
3. Rijindeal
4. Triple DES

Note: For all of these methods, we have some required parameters:

• Specify a method
• Use a Private Key

What is a Private Key?

Private Key is a string with specific Length.
For DES method, the length of Private key string must be 8 characters.
For RC2 method, the length of Private key string must be Minimum 7 characters.

What is Initialization Vector?

The purpose of the Initialization vector is to prevent dictionary attacks. For example, without an initialization vector, "password" will always encrypt to the same thing, which makes a dictionary attack easier. If something unique for each entry (such as row ID) is used as an initialization vector, an attacker would have to apply a dictionary attack to each row individually, as opposed to the entire DB. ( Thanks for Wk633...)

Using the Code

For implementing encrypt a string, we have 2 classes:

• EncryptEngine
• Encryptor

//
// EncryptEngine: // Core of Encryption class 
Public class EncryptEngine 
{ 
    EncrypltionAlgortim AlgorithmID; 
    Vector Keyword 
    Public EncryptEngine()
     { 
        // Constructor … Initializing Parameters 
     } 
    
    Public GetCryptTransformer() 
    { 
        // Return ICryptTransformer by Specified algoritm 
    } 
} 

Public class Encryptor 
{ 
    EncryptEngine _engine; 
    String _privateKey=””; 
    Byte [] IV; 
    // Initialization Vector ==> Needs for decrypt 
    Public Encryptor(ALgoritmID,PrivateKey) 
    { 
        // <CODE>Initializing Encrypt Engine by setting Method and PrivateKey 
    }
     Public string Encrypt(string SourceString) 
    { 
        // // … translation 
        // Return EncryptedString; 
    } }//

Executing Program

When you set Method of Encryption and set Private Key, Press on Encrypt Button.

The program generates 2 parameters:

1. Initialization Vector
2. The Result ( encrypted string )

   

For decrypting a string, we need 2 parameters.
The program uses an Initialization Vector and result to decrypt a string.