By Jo Twist
BBC News Online
The government has started a large-scale test of the biometric technology to be used in UK identification cards.
Biometric technology will improve as it is used, scientists say
The technology is to be provided by a consortium of companies, including SchlumbergerSema, NEC, Identix and Iridian.
The scheme will help UK citizens play a "full role in our increasingly global and technologically complex world", the Home Office says.
But concerns about the effectiveness of using biometric methods to combat identity fraud and global terrorism surround the practicalities and applications of the technology.
"The technologies like iris scanning are accurate enough for the ID cards application but only providing they are implemented properly and one has appropriate fall-back processes to deal with exceptional cases," Dr Tony Mansfield, chief research scientist and biometrics expert at the National Physical Laboratory, told BBC News Online.
Such "exceptional cases" could be someone who simply has very long eyelashes, or it could be something more serious like a disability that affects the collection of biometric data.
An important part of the national trials, involving 10,000 people, will be to scrutinise the processes put in place to cope with these cases, rather than purely the technology itself.
The key to biometrics is the amount of randomness and complexity that they contain, say experts in the field.
Eyes have it
Irises are a more accurate way of verifying identity, according to Professor John Daugman, the Cambridge professor who developed international algorithm standards for iris recognition.
In simple terms, explains Dr Mansfield, this means that one iris is more accurate than one finger in discriminating who is who.
The added strength of iris recognition is that it never makes "false matches", say experts.
There has never been a documented case of an iris comparison mistaking one person for another.
But the potential weakness of iris recognition is that it can fail to make a match at all.
This can happen if less than half of an iris is visible between the eyelids, or the eye is out of focus, or too distant, according to Professor Daugman.
The two-stage trials will mean volunteers will report to centres across the country to sit in front of a purpose-built booth.
The booth is equipped to record images of the face, iris and fingertips - biometric data which are unique physiological characteristics. This will be the "enrolment stage".
The second stage, a few minutes later, will involve a verification process, where a participant's biometric is compared to what has been collected.
The plan is to eventually embed a microchip containing this information into an identification document.
Fingerprints will be scanned electronically, with no ink used
The chip will be mandatory in passports renewed from 2007/8.
From mid-2005, the data will be in the form of a digitised photograph which will be matched with the identification document's chip.
Both the photo and the chip will have the digital signature of the UK Passport Service (UKPS).
Iris scanning is already being used at Schiphol Airport in Amsterdam, Toronto, Vancouver and six other Canadian airports.
By next summer, 10 UK airports will be using iris scanning technology, with a planned roll-out awaiting budget approval for all 141 UK ports.
There is no doubt the trials are a huge undertaking and the biometric ID scheme is an ambitious project.
There are still many uncertainties about the effectiveness and practicalities of such a massive scheme, including acceptable margins of error and the overall costs.
These will be clearer after the UKPS trial, according to the Home Office.
David Blunkett has admitted the scheme is not going to directly stop the possibility of terror strikes in the UK.
But, he said, it would make a big difference to the work of counter-terrorism and security services when it comes to verifying if people are who they say they are.
"The biometric technology, if implemented properly, has the capability of delivering what is required," agrees Dr Mansfield.
Using biometric identifiers as proof of identity will, says Dr Mansfield, help in the fight against terrorism - but only indirectly.
Biometrics are there as a helpful tool, but the fact remains that only a minority of terror suspects use false identification anyway.
The technology has not really been tried in a similar application on such a large scale before. Although fingerprinting has been used on systems as large as this in the UK, it has not been used for "civilian applications".
But at least there is one certainty. As the scheme is rolled out and deployed, the technology will improve, says Dr Mansfield.
Facial scanning: A camera with appropriate software records face contours and converts them into code. A computer processes the data and checks against stored record.
Iris imaging: Software scans a digital image of the iris to compare its unique pattern with all those stored.
Fingerprinting: A scanner reads the ridge patterns and compares the converted code with those on a database.