Thanks
Guy, - the pollworker did restart the unit and eventually put the unit back in
election mode. It did not require
redownloading the card. Am I
missing something in your explanation to understand
this?
John
-----Original
Message-----
From:
owner-support@gesn.com [mailto:owner-support@gesn.com]On Behalf Of Guy Lancaster
Sent: Thursday, January 18, 2001 2:41
PM
To: Support
Subject: Memory card checksum errors
(was: 2000 November Election)
This is an overview on what memory card
checksum errors are. Exactly what causes them is a separate question.
The memory card is very simply a
programmable memory device with a battery backup. The Accu-Vote accesses
this memory directly. If something goes wrong when the Accu-Vote is
writing new data to the memory card or if the Accu-Vote crashes (as computers
have been known to do) and writes to random memory locations, then the data on
the memory card may be corrupted (nasty word I know but it fits). All
this means is that the data is modified in an unintentional manner. This
could also happen without an Accu-Vote through static discharge or some types
of radiation (i.e. old airport scanners, cosmic rays???).
There are several mechanisms that we
could use to detect this. We use the simplest of these which is to treat
the data as a series of numbers and store totals of sets of those numbers as
separate data known as checksums. If the data has been modified without
updating the checksums, then the checksums will fail to add up.
The Accu-Vote keeps three different
types of checksums for three different classes of data. These are text,
counters, and precinct. The text checksums cover all the titles and
names that are used mostly just for printing reports. Since the text
data does not affect the other operations, we check it only occasionally and
we allow most operations to continue after a warning.
The counters and precinct data are
considered critical and the Accu-Vote is largely inoperable when these
checksums fail. We do support the option to clear the counters if only
they have been affected and then counting may be restarted. However
there is no way to recover from corruption of the precinct data other than to
clear and re-download the memory card.
All checksums are validated upon
insertion of a memory card or at power on. Thus this is the most common
time to detect problems. However the counter and precinct checksums are
validated every time a new ballot is scanned. If an error is detected,
counting is aborted.
Now to Lana's questions. The above
should answer everything other than why erroneous data managed to
upload. I see two possible explanations. One is that the data was
corrupted after the checksums were validated. In this case the errors
would show the next time the checksums were checked. The other
possibility is the miniscule chance that the erroneous data managed to add up
to the correct checksum. The checksums are stored as totals ranging from
0 to 65535 so the chance of this happening are less than 60,000 to 1 just
based on that. Other factors add to this to make it extremely
unlikely. However in this case the card would not later show checksum
errors.
So John, can you satisfy Lana's request
from this? I can't without more details.
Guy
John McLaurin wrote:
Please see below and let me know what
you think. Tab, one of these issues
we discussed - it's the one were
we printed the audit report showing the
check sum error and the poll
worker restarting the unit.
Please let me know what you guys think.
John
-----Original Message-----
From:
Lana Hires [mailto:lhires@co.volusia.fl.us]
Sent: Wednesday, January 17, 2001 8:07 AM
To: jmglobal@earthlink.net;
Glanca@ges.com
Cc: Deanie Lowe
Subject: 2000 November Election
Hi
Nel, Sophie & Guy (you to John),
I need some answers! Our
department is being audited by the County. I have
been waiting for
someone to give me an explanation as to why Precinct 216
gave Al Gore a
minus 16022 when it was uploaded. Will someone please
explain this
so that I have the information to give the auditor instead of
standing
here "looking dumb". I would appreciate an explanation on why the
memory cards start giving check sum messages. We had this happen in
several
precincts and one of these precincts managed to get her memory
card out of
election mode and then back in it, continued to read ballots,
not realizing
that the 300+ ballots she had read earlier were no longer
stored in her
memory card . Needless to say when we did our hand
count this was
discovered.
Any explantations you all can give me will
be greatly appreciated.
Thanks bunches,
Lana