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Posted 28 Dec 2006

Encrypt and Decrypt a String

, 29 Dec 2008 CPOL
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In this article, you can encrypt a string and decrypt it again
Sample Image - Encrypt_an_string1.gif


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.


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

Class diagram of program

// 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

After Encryption excuted

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 )

    After Encryption excuted

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


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Amir Mehrabi-Jorshari
Software Developer (Senior) Omid Farda IT Company
Iran (Islamic Republic of) Iran (Islamic Republic of)
Master of Science in Computer Engineering

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Comments and Discussions

Generalerror Pin
zhaojicheng9-Apr-07 21:33
memberzhaojicheng9-Apr-07 21:33 
GeneralRe: error Pin
Amir Mehrabi J.9-Apr-07 21:56
memberAmir Mehrabi J.9-Apr-07 21:56 

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