RE: Java Compression & Encryption

[<Vikrant.Verma@alltel.com>]

I wonder what this post is doing on  AJUG. What u really need is a crypto newsgroup. Anyways let me share my 0.02$.
I would suggest you to use PKZIP, the decision of this algo has nothing to do with unicity but rather its the simplicity of implementation. Java already has an implementation of PKZIP and it should not be hard for you to figure out how to use it. Also unicity can be better answered if you use combination of the following techniques compression, scrambiling, expanding and substituting data. 
I noticed that you are a college student, so maybe basing my answer on simplicity will not appeal to you. So let me explain how pkzip will work wrt increasing unicity distance. Unicity is simply the minimum length of the text that can be uniquely deciphered by trying brute force attack on a large encrypted message. This can help an attacker to find the key used to encrypt the text. This kind of an attack depends highly on readability of the message  Once the data is compressed the readability of the message is reduced. A compressed data will always have a higher unicity and the unicity distance will always be proportional to compression. On the hindsight the higher the compression the faster the brute force attack, if the attacker can guess the compression algorithm. Compression factor of any non lossy algorithm is directly dependent on the data set. So an algorithm which is good for a data set may not be as effective for another. Therefore if i may generalize, any compression algorithm will serve the purpose and pkzip is easily available.
 
-Vikrant
 
PS: Software Rule No 1: KISS
 
-----Original Message----- 
From: Shakti Saran (College of Computing) [mailto:snsaran@cc.gatech.edu] 
Sent: Fri 6/27/2003 4:08 PM 
To: ajug-members@ajug.org 
Cc: 
Subject: Java Compression & Encryption



	I am trying to build a small application that will read from the database, compress and encrypt the information and send it out as an email attachment. I am using Rijndael for security. I want to compress information inorder to increase the unicity distance. I need help in selecting a good compression alogrithm that will do the above.
	 
	Thank you for the help.
	 
	Shakti Saran
	Computer Science & Discrete Math
	Georgia Tech