Re: Alternatives to a single bar code

From: David Mertz <voting-project_at_gnosis_dot_cx>
Date: Wed May 05 2004 - 12:31:09 CDT

Arthur Keller wrote:
> 1. Will someone please describe the length of the bar code in bits in
> components:
> a. header info (including election date, machine number, ballot id,
> etc.)
36 bits:
We do NOT need to explicitly contain spelled out version of all
associated information. Rather, a globally unique ID lets us look up
the election data in an external database (and as a reference into a
corresponding ballot-election.xml file).

> b. votes
< 80 bits:
Or at least that is my current assumption, pending historical
demonstration to the contrary.

> c. 2 DSS blocks
We don't need two distinct signature blocks. One doubly-signed block
is fine. Actually, I don't even think we need doubly-signed... but

I think a 48-64 bit signature is more than sufficient. Compromise of a
key only affect ONE voting machine, so we only have to increase the
forgery costs to make that too expensive. It's not like a global "the
whole election" key, that would be worth much more to crack.

> d. end-to-end check-code
A CRC-16 does what we need. This is SOLELY to protect against
accidental data corruption. Some barcodes, like Code128, already
contain their own error detection as well.

However, we can probably eliminate this too, since a signature already
provides error detection (if it doesn't match, it's time for manual
examination anyway... even if the mismatch is just because of a smudged

> e. ECC block
Not needed. Error check is plenty to indicate fallback to manual
examination of printed votes. In fact, if the ECC is needed, that
indicates a situation where we should manually examine the ballot to
look for what went wrong.

> f. padding for obscuring
Not needed. Obscuring the votes in a manner similar to the demo is
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Received on Mon May 31 23:17:16 2004

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