[E-voting] Spontaneous bit flipping in Belgium

fergal at esatclear.ie fergal at esatclear.ie
Thu Dec 4 13:34:54 GMT 2003


The latest EDRI-gram - http://lwn.net/Articles/61204/ - has a reference to
an incident in Belgium:

---
The Belgian e-voting expert David Glaude reports an incident with e-voting
in Belgium. Not widely published it took place on 18 May 2003, in the
municipality of Schaerbeek. The total number of preferential votes cast on
a specific candidate was higher than the total number of votes for his
list. A series of tests was conducted on the computer of the president of
the voting committee, but the error could not be reproduced. The
difference in votes was exactly 4.096, leading the research-team to the
conclusion that the error was probably due to a spontaneous inversion of a
binary position in the read-write memory of the PC.
---

For the non-techies: An abacus has lines of beads, each line has 9 beads,
the first line is for 1s, the second for 10, the third for 100s etc. Now,
imagine you are counting the votes on an abacus and a strong gust of wind
blows one of your abacus beads from one side to the other. If it happened
on the 1s line your result would be out by 1, if it happened on the 10s
line your result would be out by 10, if it happened on the 100s line, your
result would be out by 100 and so on. Computers are similar except, each
line on the computer's abacus only has 1 bead and the different lines count
1s, 2s, 4s, 8s, 16s, 32s etc (keep doubling the number). The equivalent of
a gust of wind for a computer is a cosmic ray or a radiation particle or
something.

What seems to have happened in this case is that the 4096s line on the
abacus for this guy's vote got flipped, this can happen on any computer,
it's rare but this demonstrates that it's a real possibility.

It was discovered because it added 4096 to the total which meant he got
more preferences than was possible but would anyone have noticed if it had
flipped a different bit and added 256 votes maybe putting him in the lead
but without raising any alarms? What if it had subtracted 4096?

David, can you expand on this event and the resolution? I think this is
absolutely crucial. What was done, did they decide that even though there
was no way to prove it that the 4096 was due to a binary error and so his
total was reduced by 4096? How did they decide what the "correct" total was
without a paper trail?

F



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