The biometric technique that has been selected for incorporation into the new UK national ID card has been undermined in the scientific press. New Scientist has reported that the technique of iris scanning is not as perfect and infallible as the Home Secretary (Minister of Internal Affairs) has claimed. The article alleged that the technology was prone to failure and that its success could not be guaranteed if used on a national scale.

New Scientist reported that the key problem "is the limited accuracy of biometric systems combined with the sheer number of people to be identified. The most optimistic claims for iris recognition systems are around 99 per cent accuracy - so for every 100 scans, there will be at least one false match".

"This is acceptable for relatively small databases, but the one being proposed will have some 60 million records. This will mean that each person's scan will match 600,000 records in the database, making it impossible to stop someone claiming multiple identities. Even if they already had one or more records in the database, these would be swamped by the hundreds of thousands of false matches".

The magazine quoted Simon Davies, director of EDRI member Privacy International, as saying that the technology's performance would not improve in the foreseeable future.

The Guardian took Davies critique to a more complex level. "A system with 0.999999 reliability would make a false match, on average, once every million times - great for verification. But for identification, the chances of the system correctly comparing someone with its entire database can be calculated by its success rate to the power of the database size. If that is two, with the example above it would be 0.999999 squared, or 0.999998. That means 100 people would produce a 0.9999 success rate, 100,000 a 0.9048 success rate. A database holding the whole UK population - 50 million - leads to less than one in five thousand billion billion - in other words, useless".

Media extensively reported the issue, first through Reuters and then in the International Herald Tribune. The allegations sparked a lengthy and heated email exchange between Davies, iris scanning inventor John Daugman, and many of the world's leading biometric experts. New Scientist will publish some of the exchanges this week.

'Biometric cards will not stop identity fraud', New Scientist (21.11.2003)
http://www.newscientist.com/news/news.jsp?id=ns99994393

'Report faults biometric ID card plans', Reuters (20.11.2003)
http://www.iht.com/articles/118306.html

'Image Problem', The Guardian (20.11.2003)
http://www.guardian.co.uk/online/story/0,3605,1088437,00.html