Re: Bar code choice

Date: Sat Sep 13 2003 - 13:00:20 CDT

In a message dated 9/13/03 1:46:23 AM Pacific Daylight Time, jan@it.uu.se
writes:

> As Edward Cherlin suggested, one can use bitwise xor to obscure the
> bar code:
>
> http://gnosis.python-hosting.com/voting-project/August.2003/0286.html
>
> I suppose there is not a problem if the ballot number can be visually
> read from the bar code by a person that recognizes Code 128. Then one
> can xor the rest of the bit string with the ballot number (repeated).
> This will not increase the length of the bar code at all.
>
Good.

> For example:
>
> bit string = 100110010111010110
> ballot number 13 = 1101 binary
>
The ballot number is supposed to be a 4-digit number. I mentioned that it
could be represented with two symbols. If I'm understanding you correctly, we
will have 95 symbols ... 95*95 = 9025 possible ballot numbers. We will want
more for the production system but for the demo this is plenty. If we're not
going to use compression, I'd rather save the extra character from the barcode.

For the production system, we will definitely want to use compression since
it's possible to have far more than 116 bits. Doug Jones shows us 228 and 235
position punch card ballots. There is even a 312 position ballot there.

I still would not want to rule out compression for the demo. With your
scheme, you still have to come up with a way to do long integer math within Python
to convert the 116 digit binary number to a 35 (or less) digit decimal number.
It might not be that time consuming to write the compression algorithm we
need (or maybe we can find one already done). I would ask Arthur to do it but
right now he is contributing to the overall project by working on an NSF grant
proposal. If the choice is taking away time from the NSF proposal to work on
the compression function, I'd rather have him stick to the NSF proposal.

Alan D.
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Received on Tue Sep 30 23:17:04 2003

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