don't like the price? change the barcode!

[Paul Lambert]

The membership cards at many stores use barcodes (
http://www.nocards.org/ ).

While most have a magnetic stripe, they are often entered using
a bar code scanner (especially when the mag stripe accidentally gets
erased).

Many home labeling machines are able to print bar codes.  White 
home made bar code labels placed on the card are difficult to 
distinguish from the original card.

For example, the 'Safeway Club Card' that I'm currently using
is '41002004587'.  Anyone with a label machine can now identify
themselves at Safeway using this number.  This identification
will effectively prevent the fines imposed by Safeway for
those that refuse to identify themselves.


Paul


>-----Original Message-----
>From: Perry E. Metzger [mailto:perry at piermont.com] 
>Sent: Friday, April 11, 2003 9:57 AM
>To: cryptography at wasabisystems.com
>Subject: don't like the price? change the barcode!
>
>
>
>A trivial way to attack automated bar code scanners: change 
>the barcodes on products you are buying. I think actually 
>doing it is reprehensible, but on the other hand it does show 
>what happens when people start applying lessons from computer 
>security to the real world:
>
>http://www.re-code.com/
>
>A Salon article on the same topic:
>
>http://www.salon.com/tech/feature/2003/04/10/barcode/index.html
>
>-- 
>Perry E. Metzger		perry at piermont.com
>
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