From: "Peter Trei" <trei@process.com>
Date: Tue, 5 Sep 95 07:35:31 PDT
To: cypherpunks@toad.com
Subject: Re: VCRPLUS Huffman code
Message-ID: <9509051435.AA15596@toad.com>
MIME-Version: 1.0
Content-Type: text/plain



> Has anyone worked out the VCRPLUS code?

It was partially broken a few years ago, and the results published in
Cryptologia. I have a xerox in a carton somewhere. 

The break was for codes up to 4or 5 digits long, if I recall - this covers
most of the major timeslots on the main stations. Longer codes
cover odd timeslots on less popular stations.

Code which implemented this partial crack was published on the net,
and the VCR+ people got very upset about it - apparently they make
money selling the codes to TV Guide and newspapers. It's protected
as a trade secret, not a patent.

It used a combination of lookup tables and Huffman codes, and
included a certain amount of obfuscation to resist cracking.

Peter


Peter Trei
Senior Software Engineer
Purveyor Development Team                                
Process Software Corporation
http://www.process.com
trei@process.com