The Devil is in the details, Chapter IV. One voter, one vote: indelible ink or fingerprint machines?

Translation published here of this post.

The first time I heard about the fingerprint capturing machines I was surprised at the large number of technical and logistical challenges that would have to be overcome in order to install such a system and I asked myself if the possibility of multiple votes in Venezuela, justified the purchase and installation of such an expensive and complicated system. In fact, in a pamphlet by COGENT systems, the winner of the bidding process, it is specified that never before had such a system been implemented, with so many technical challenges, as the one that was installed in Venezuela[1].

But, independently of whether it is, or not, technically feasible to put such a system in practice with success, the question that has been going around in my head is if the Directors of the CNE [2] that defend the fingerprint machines are right, if, effectively, the fingerprint machines guarantee the premise of

One voter, one vote

I decided then to investigate a little bit about systems for the recognition of fingerprints

I found that such systems are used specially for criminal identification and that there are two types of problems that an be tackled.

The first one is called “1:1” or “one-to-one”,. In this one, the fingerprint is compared with another one that is believed to be that of the same person. For example the fingerprint of Pedro Perez is compared with that which the authorities have of Pedro Perez and it is determined whether it happens to be the same fingerprint or not.

The second problem is the “1:N” or “one to many”. In this case you want to know if the fingerprint of Pedro Perez is found among a set of fingerprints stored by the authorities. It is obvious that the second case is more complicated and that it can yield a higher percentage of errors than the first.

Logically, in an election, I told myself, both types of recognitions have to be performed to determine if Pedro Perez is who he says he is and later determine if he already voted.

I could not obtain official information about this, but I have been told that in the Venezuelan elections only the second type of verification was performed, that is, the “one to many”, while the determination if the person was Pedro Perez was done with the National ID card, called cedula.

Following this, I tried to learn more about the ways to verify such systems. I found that the then National Institute for Standards (NIST) of the US Government, performs tests to determine the precision of various commercial systems, including among them, the systems made by Cogent Systems.

The evaluation is made following two complementary criteria, the TAR and the FAR. According to one of the NIST reports [3], the TAR (True Accept Rate) is defined as the fraction of correct identifications by the identity algorithm, while the FAR (False Accept Rate) is defined as the fraction of false positives in recognizing an identity.

Now, even thought the Cogent systems received excellent reviews in the independent tests that were performed, the accuracy rates were not 100%

Let’s see, for example, the results relative to the identification systems of individuals presented by NIST at the Biometrics Congress in 2004 [4] (see page 16). According to the presentation, it was found that in the tests for the identification of visitors, Cogent’s technology had a TAR of 98% when databases of high quality fingerprints were used and it could go down as low as 47% when databases with low quality fingerprints were used. In both cases, a value of FAR (false positives) of 0.01% was found.

Let’s set aside these numbers in our minds for the moment and let’s make an analysis of the possible results of the application of fingerprint capturing machines in the Venezuelan elections.

When a vote arrives at the fingerprint machine, there are two possibilities: that he is an honest voter (He has not voted yet) or he is a voter that cheats (He already voted and wants to vote again). On the other hand, the verification system for the fingerprint capturing system can respond correctly or erroneously if the voter already voted or not or even may not find the fingerprint or take longer than the time required to do it. We then have the following possibilities:

	True state of the voter	System Response	Interpretation f the result	What does the law say in this case? [5]
Case1	Did not vote	Did not vote	correct	Allows vote
Case2	Did not Vote	Voted	error	Does not allow vote
Case3	Did not vote	Can’t find it	error	Allows vote
Case4	Voted	Voted	correct	Does not allow vote
Case5	Voted	Did not vote	error	Allows vote
Case6	Voted	Can’t find it	error	Allows vote

As you can see, it is a system much more complex than a simple system to identify Pedro Perez whether individually or with a database of many fingerprints. Thus if you were to design tests to evaluate the trustworthiness of the answers of such systems, the levels of precision have to be much tighter than those found in identification systems.

Now, suppose for a moment that we can apply the TAR given above for our system. That is, let’s say that the TAR is 98% for excellent fingerprint databases and goes down to 47% for low quality fingerprints. The TAR gives the rate for a good performance which, in our system, consists of cases 1 and 4. Let’s say also that only 25% of the fingerprints stored in the database of the CNE are of low quality and finally, let’s say that there are 10 million voters. In this case, we would obtain that only 8.52 million voters are in the category of “One Person, one vote”, the other 1.48 million missing would fall under the category of errors. According to the law, in cases 3,5 and 6 they are allowed to vote and, among them, we don’t know if there are any cases of multiple votes.

Of course, if the CNE were a serious organization, it would have already informed us of how many cases there were of multiple votes and false positive recognitions by the little machines. After spending so many millions on them, Venezuelans deserve to know what are the TAR and other statistical errors of such an onerous system. No?

One thing is certain. The CNE is NOT right: the fingerprint machines DO NOT GUARANTEE the principle of “One Voter, one vote”

….and the indelible ink is much cheaper and much faster….

References

[1] COGENT document, “One Voter one Vote”.

[2] El Nacional, 30 de Julio, page A2. Reference to CNE Directors Lucena y Hernández.

[3] Fingerprint Vendor Technology Evaluation 2003, Análisis Report. National Institute of Standards and Technology.

[4] Wilson, C.L., “NIST Patriot Act Biometric Testing”, Biometrics Conference, 2004.

[5] CNE, Resolución N° 041022-1621, “Normas sobre el procedimiento de captación de huellas dactilares y garantía del principio de un elector un voto en las elecciones regionales 2004”.

Note: after publishing this post, a reader indicated that my sentences about the CNE not publishing the data was not accurate since the information on the number of "cheaters" in the elections have been published in a table of an Ultimas Noticias article of July 30, 2006 (page30). According to that table, between the Revocatory Referendum and the governors elections there has been a total of 53 cheaters.

Such a value shows that not only the system is not 100% reliable and produces mistrust among the voters, but its cost and the political anxiety it has created cannot be justified by the abysmally low cheating statistics.

In the same table, I discovered some data called "grey zones" that show the number of voters that could not be properly identified by the system. The numbers shown are quite high and seem to confirm even more strongly that the "one voter, one vote" principle cannot be guaranteed.

Another reader indicated that in the CAPEL report there was information about the digital fingerprints. A quick review made me realize that my hypothesis of 25% of bad quality fingerprints was optimistic. Therefore, the errors produced due to the imprecision of the fingerprints is even higher.

In other words, the more I learn details about this system, the more I like the indelible ink.

That is why I say that the Devil is always in the details.