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Encrypt and Decrypt a String

By , 29 Dec 2008
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Sample Image - Encrypt_an_string1.gif

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

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.

License

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

Comments and Discussions

 
GeneralMy vote of 5 PinmemberfatemeRokni10-May-13 8:10 
AnswerRe: My vote of 5 PinprofessionalAmir Mohammad Nasrollahi9-Aug-13 21:15 
GeneralMy vote of 5 Pinmembermanoj kumar choubey29-Mar-12 20:16 
QuestionHow to handle strings over more than one line Pinmembergeorgebaker14-Mar-12 12:46 
NewsIf you want to encrypt a whole filesystem Pinmemberjp7317-Nov-07 17:59 
NewsTwo other related encryption articles in CodeProject ... PinmemberTony Selke27-Sep-07 6:52 
Generalerror Pinmemberzhaojicheng9-Apr-07 21:33 
GeneralRe: error PinmemberAmir Mehrabi J.9-Apr-07 21:56 
GeneralRandomness PinmemberJeffrey Walton5-Jan-07 3:09 
GeneralA FullFledged One PinmemberVasudevan Deepak Kumar4-Jan-07 19:51 
GeneralEnglish PinmemberAmir Mehrabi J.4-Jan-07 17:24 
GeneralRe: English Pinmembertelwah16-Feb-09 6:16 
Generalgrammar Pinmemberwk6333-Jan-07 8:14 
GeneralRe: grammar PinmemberMrBobIsMean30-Dec-08 9:43 
GeneralRe: grammar Pinmemberwk63330-Dec-08 9:59 
GeneralClass Diagram PinmemberAmir Mehrabi J.2-Jan-07 6:20 
Generalsoftware Pinmembereconner2-Jan-07 4:39 

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