Re: Crypto question: Hashing ultimate output for local use

From: Arthur Keller <voting_at_kellers_dot_org>
Date: Mon May 02 2005 - 07:34:52 CDT

At 1:57 AM -0400 5/2/05, David Mertz wrote:
>* November 2-8: Poll workers get their shiny CDs at polling places.
>The Republican poll watcher says: "I don't trust the authenticity of
>that CD," and demands to run the hash on her Windows laptop (hash
>turns out to be 9876ffdd123). The Democratic poll watcher says: "I
>don't trust the authenticity of that CD," and demands to run the
>hash on her MacOS machine (hash turns out to be 9876ffdd123). The
>Green poll watcher says: "I don't trust the authenticity of that
>CD," and demands to run the hash on her Linux machine (hash turns
>out to be 9876ffdd123).
>No one anywhere in the sequence trusts anyone else, nor should they,
>nor do they need to.

Great narrative. One missing part.

Then the poll worker runs a hash on some standalone machine to ensure
that none of the checkers has added another session to the CD-R or
mucked with it in some other way. (The poll worker should do this
after each of the poll watchers, to narrow down who did it.)
Otherwise, the last poll watcher can modify a CD.

The software should also do a self check of the hash when it starts,
and it should print the hash on the startup page. (Although if
maliciously tampered with, it could lie about the hash on the

A standalone CD-R (or DVD-R) hasher that displays the hash code and
other identifying info on an LCD screen would make a good product.
The hashing code could be in firmware in a stripped down,
firmware-resident, "operating" system. The device could either have
no ports or just a parallel printer port for documenting the display.
(I figure the parallel printer port is the least corruptible port,
but maybe someone knows how the printer could corrupt the standalone
CD-R hasher somehow. The device would look something like an Mac
Mini, except for the LCD display and the shortage of ports.

Best regards,

Arthur M. Keller, Ph.D., 3881 Corina Way, Palo Alto, CA  94303-4507
tel +1(650)424-0202, fax +1(650)424-0424
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Received on Tue May 31 23:17:05 2005

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