Web Development

  Homes arrow Web Development arrow XOR-Encryption
 Webmaster Tools
Base64 Encoding 
Browser Settings 
CSS Coder 
CSS Navigation Menu 
Datetime Converter 
DHTML Tooltip 
Dig Utility 
DNS Utility 
Dropdown Menu 
Fetch Content 
Fetch Header 
Floating Layer 
htaccess Generator 
HTML Encoder 
HTML Entities 
IP Convert 
Meta Tags 
Password Encryption
Password Strength
Pattern Extractor 
Ping Utility 
Pop-Up Window 
Regex Extractor 
Regex Match 
Scrollbar Color 
Source Viewer 
Syntax Highlighting 
URL Encoding 
Web Safe Colors 
Forums Sitemap 
Weekly Newsletter
Developer Updates  
Free Website Content 
 RSS  Articles
 RSS  Forums
 RSS  All Feeds
Write For Us 
Contact Us 
Site Map 
Privacy Policy 
  >>> SIGN UP!  
  Lost Password? 

By: Developer Shed
  • Search For More Articles!
  • Disclaimer
  • Author Terms
  • Rating: 3 stars3 stars3 stars3 stars3 stars / 2

    Table of Contents:

    Rate this Article: Poor Best 
      Del.ici.ous Digg
      Blink Simpy
      Google Spurl
      Y! MyWeb Furl
    Email Me Similar Content When Posted
    Add Developer Shed Article Feed To Your Site
    Email Article To Friend
    Print Version Of Article
    PDF Version Of Article




    by: cprogramming.com


    Exclusive-OR encryption, while not a public-key system such as RSA, is almost unbreakable through brute force methods. It is susceptible to patterns, but this weakness can be avoided through first compressing the file (so as to remove patterns). Exclusive-or encryption requires that both encryptor and decryptor have access to the encryption key, but the encryption algorithm, while extremely simple, is nearly unbreakable.

    Exclusive-OR encrytion works by using the boolean algebra function exclusive-OR (XOR). XOR is a binary operator (meaning that it takes two arguments - similar to the addition sign, for example). By its name, exclusive-OR, it is easy to infer (correctly, no less) that it will return true if one, and only one, of the two operators is true. The truth table is as follows:
    A   B    A XOR B
    T   T       F
    T   F       T  
    F   T       T 
    F   F       F
    (A truth table works like a multiplication or addition table: the top row is one list of possible inputs, the side column is one list of possible inputs. The intersection of the rows and columns contains the result of the operation when done performed with the inputs from each row and column)

    The idea behind exclusive-OR encryption is that it is impossible to reverse the operation without knowing the initial value of one of the two arguments. For example, if you XOR two variables of unknown values, you cannot tell from the output what the values of those variables are. For example, if you take the operation A XOR B, and it returns TRUE, you cannot know whether A is FALSE and B is TRUE, or whether B is FALSE and A is TRUE. Furthermore, even if it returns FALSE, you cannot be certain if both were TRUE or if both were FALSE.

    If, however, you know either A or B it is entirely reversible, unlike logical-AND and logical-OR. For exclusive-OR, if you perform the operation A XOR TRUE and it returns a value of TRUE you know A is FALSE, and if it returns FALSE, you know A is true. Exclusive-OR encryption works on the principle that if you have the encrypted string and the encryption key you can always decrypt correctly. If you don't have the key, it is impossible to decrypt it without making entirely random keys and attempting each one of them until the decryption program's output is something akin to readable text. The longer you make the encryption key, the more difficult it becomes to break it.

    The actual way exclusive-OR encryption is used is to take the key and encrypt a file by repeatedly applying the key to successive segments of the file and storing the output. The output will be the equivalent of an entirely random program, as the key is generated randomly. Once a second person has access to the key, that person is able to decrypt the files, but without it, decryption is almost impossible. For every bit added to the length of the key, you double the number of tries it will take to break the encryption through brute force.

    C++ uses ^ for bit-level exclusive-OR. To encrypt a single character you can use char x=x^key; if you have a key of one byte. To encrypt a string of characters with a longer key, you can use something akin to the following code:
    #include <iostream.h>
    int main()
    char string[10]="A nice cat";
    char key[10]="ABCDEFGHIJ";
    for(int x=0; x<10; x++)
    return 0;
    The program encrypts each character in the string using the ^ bit operator to exclusive-OR the string value with the key value for each character.
    DISCLAIMER: The content provided in this article is not warranted or guaranteed by Developer Shed, Inc. The content provided is intended for entertainment and/or educational purposes in order to introduce to the reader key ideas, concepts, and/or product reviews. As such it is incumbent upon the reader to employ real-world tactics for security and implementation of best practices. We are not liable for any negative consequences that may result from implementing any information covered in our articles or tutorials. If this is a hardware review, it is not recommended to open and/or modify your hardware.

    More Web Development Articles
    More By Developer Shed



    - On Page SEO for New Domains
    - Improve Your Site`s Speed
    - Safari Books Online Review
    - Creating an Estore From the Ground Up
    - Most Common SEO Mistakes Developers Make
    - Making the Most of Your Titles and Meta Desc...
    - Five Ways Using Flash Can Damage Your Site
    - A Web Designer`s Guide to Colors
    - Use Webstarts to Create a Free Site
    - More Than Just Looks. How Your Web Design C...
    - How to Design Content Pages
    - Mint Review
    - Make Your WordPress Website Look Professional
    - How to Create a Mobile Web Site
    - Meta Tags: Still Useful?

    Developer Shed Affiliates


    © 2003-2019 by Developer Shed. All rights reserved. DS Cluster - Follow our Sitemap