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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----- 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 Please let me
know what you guys think. John -----Original
Message----- Hi Nel,
Sophie & Guy (you to John), |