Re: Alternatives to a single bar code

From: Steve Chessin <steve_dot_chessin_at_sun_dot_com>
Date: Wed May 05 2004 - 05:04:33 CDT

>From Wed May 5 02:22:48 2004
>Date: Wed, 5 May 2004 02:22:35 -0700 (PDT)
>Subject: Re: [voting-project] Alternatives to a single bar code
>On Wed, 5 May 2004, Steve Chessin wrote:
>> The nice thing about multiple bar codes is that they scale.
>I'm concerned that the presence of multiple bar codes could lead to reader

I don't understand. How would the presence of multiple bar codes lead
to reader misreads?

>But more importantly, I'm concerned about attacks that could occur should
>individual bar-codes from different ballots be scanned as if they were
>from the same ballot.

This seems to assume that ballot counting is done by using a hand-held
scanner. This attack is not possible with a flat-bed scanner that
scans the entire ballot at once. (Well, it is possible, if you take a
pair of scissors and cut and paste the old fashioned way, but I assume
that the other people in the polling place observing you count the
ballots will stop you from doing this.)

If the bar codes are used for tabulation as well as audio output (and I
don't recommend this), you could also include with each bar-code the
ballot number. Remember, I'm recommending OCR printing and flat-bed
scanning for tabulation.

>This is why I prefer one bar code that contains all the data (that bar
>code would be replicated for protection against damage, but it would be
>the same bar code.)
>I don't see any hope that we will be able to stay within the data limits
>of the 1 dimensional bar codes - we are already pushing the limit, even
>without a digital signature message digest or end-to-end check-code. But
>the 2-D codes (e.g. PDF417) can hold about 2kbytes - about 50 to 100
>times what we are getting out of the current 1D EAN128C bar code. The
>price for a usable 1D handheld scanner is roughly $150, a 2D model costs
>about $50 more.

How many choices can that 2K hold?

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Received on Mon May 31 23:17:14 2004

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