From: David Miller <dm0@avana.net>
Date: Tue, 10 Feb 1998 11:32:20 +0800
To: cypherpunks@Algebra.COM
Subject: Re: Drivers Licenses
Message-ID: <34DFC8FA.1CECCE12@avana.net>
MIME-Version: 1.0
Content-Type: text/plain



Anonymous (remailer@htp.org) wrote:

> My question is, how much information can be stored on these strips?

The data that's stored on most of the cards (credit cards, hotel keys,
gym cards, etc.) are encoded with 5 bits per character.  I believe
that this is also known as Baudot encoding.  You can store somewhere
around 80 characters per track on "normal" cards, and most cards
contain a 1/2" magnetic stripe that can hold 4, 1/8" tracks.  So, I
would estimate that your drivers license would hold a total of about
320 characters on all four tracks with standard encoding techniques.

If you are interested in rendering only individual tracks unreadable,
it can be done.  I have done it by scratching off the magnetic
material as you described.  Of course, all tracks run horizontally
across the card, with track 1 being the track closest to the edge
of the card.  So, if you wanted to destroy track 1, you could scrape
off the 1/8" of the strip closest to the long edge of the license.

Have fun.

--David Miller

middle  rival
devil rim lad