Fingerprints and irises provide a unique reference point to verify a person's
identity in biometric security and access control applications. Greg Blackman
looks at the uses of biometric measurements
The debate still rages in the UK over the effectiveness and necessity of the
Home Office’s plans to issue ID cards as part of the national identity scheme.
The scheme was set up to provide a secure system of personal identification to
UK citizens, and as of 24 November 2008, foreign nationals living in the UK can
apply for ID cards at enrolment centres around the country.
Along with standard information, such as name, gender and date of birth, the
ID cards will contain biometric data that will be stored on a National Identity
Register (NIR). Fingerprints and a face image will both be stored on the NIR
and on the chip of the card. Leaving aside the ethical arguments surrounding
this topic, the advantage of using biometric data in addition to the standard
information is that it confirms not just that you have a valid identity card,
but that the card belongs to you.
Essentially, biometrics is the measurement of physiological or behavioural characteristics
used to verify a person’s identity. These can include face, fingerprint, and
iris recognition, as well as DNA fingerprinting and voice and signature recognition.
Automated biometric recognition techniques use complex algorithms to identify
unique patterns within images of the distinguishing trait and match them to an
individual’s file stored on a database. In this way a person’s eye or finger
can act as an ID card, providing them with access to buildings or secure areas.
Fingerprint recognition
Arches, loops and whorls make up the basic pattern of a fingerprint, and their
use as a method of identification is well established. Taking an ink imprint
of a criminal’s finger is a common procedure for most police departments. ‘Fingerprints
were arguably the second major step forward for biometrics, the first being the
signature,’ comments Paul Easton, communications director at UKB International,
a company providing access security products and services.
UKB International provides fingerprint scanners with multispectral sub-dermal
technology. ‘A multispectral imager collects information from below the surface
of the skin by reading the sub-dermal collagen ridges that form the fingerprint,
in addition to scanning the print itself,’ says Easton.
Easton explains that one of the problems with first generation scanners is that
they are dependent on contact of the fingerprint ridges with the sensor. Therefore,
anything that interfered with this resulted in an inadequate image. ‘If fingertips
were worn, dirty or wet, or the subject did not place their print exactly on
the centre of the scanner, the scanner would reject the match. Basically, the
door or switch would not work,’ he says.
Human Recognition Systems’ iris recognition equipment has been used in a project
to implement biometric methadone dispensers in prisons across England.
Multispectral sub-dermal scanners verify identity even if the fingerprint is
abraded, dirty, wet, or covered by a latex work glove. The systems are also much
harder to fool. Latex moulds of a valid fingerprint will not activate the switching
mechanism. Easton views the technique as highly robust. ‘Although both iris and
facial recognition systems are currently commercially deployed, neither is as
robust as multispectral fingerprint recognition.’
UKB International supplied its fingerprint scanners to provide gate access at
a major US theme park. A temporary fingerprint database was set up whereby visitors’ fingerprints
were held on file for the duration of their ticket, and scanners at turnstiles
provided them with easy access to rides. Easton notes that it was relatively
easy to set up a multi-tiered biometric security system, where customers were given basic
park access, whereas maintenance personnel were provided with ‘all area’ access.
The scanners provide access to millions of people and are still in operation.
Easton states: ‘Tickets, swipe cards or fobs can all be lost, stolen or “buddied”,
that is to say, passed to unauthorised persons. In addition, there is a cost
element to providing these tokens.’ Biometrics, however, can provide greater
assurance that the individual at the gate is the person who has paid.
Most commercially available fingerprint scanners involve contact of the finger
with the scanner plate. The University of Kentucky is currently developing a
fingerprint scanning technique using structured light to generate a 3D image
of the finger. A bar pattern of light is projected onto the surface of the finger
and from the distortion in the pattern, as seen by a camera placed in close proximity
to the projector, software is able to generate a 3D image.
Dr Daniel Lau, associate professor in the Department of Electrical and Computer
Engineering at the University of Kentucky, explains that contactbased fingerprint
scanners present a problem for image analysis software as the finger’s skin undergoes
a tremendous amount of distortion from pressing against the scanner. This is
especially problematic when rolling the finger across a scanner plate and leads
to a drop in recognition performance. The work being carried out at the University
of Kentucky uses a noncontact scanner to generate a 3D image of the fingerprint,
which can be virtually flattened and analysed and which minimises the problem
of image distortion associated with contact scanners.
Providing effective biometric solutions for a specific building or business is
relatively easy to achieve, as there are a limited number of employees and the
images produced by the scanners will be compatible with those on the database.
However, providing the latest fingerprint scanner, such as the one being developed
at the University of Kentucky, to national law enforcement bodies like the FBI
and expecting it to make matches from an existing fingerprint archive generated
from ink imprints is more difficult.
‘One of the great challenges for this kind of technology is making the images
compatible with fingerprint data already collected by the various law enforcement
agencies,’ says Lau. ‘The problem with using fingerprint scanners is that the
image algorithms have to filter the scanned image in such as way as to mimic
the ink records.’
Currently, the 3D scanning technology being developed at the University of Kentucky
gives a very high recognition rate between scans from the same device, but the
percentage drops significantly when it comes to comparing images from a 3D scan
with those from a 2D scan. Improving the compatibility with existing fingerprint
records is one area on which Lau’s research focuses.
Lau’s team is also using structured light to generate 3D images of the face for
facial recognition. ‘An advantage with fingerprint recognition is that it’s a
cooperative technique,’ says Lau. ‘The individual places their finger in the
scanner to give a reading. In many instances, face recognition is carried out
in an uncooperative environment, where changes in lighting and head orientation
add to the problems of obtaining a positive match.
‘Three-dimensional techniques overcome many of these issues by being able to
subtract out the shadows caused by different lighting conditions and rotate the
image to view the head at the correct angle. However, at present, the vast majority
of photo ID is two-dimensional and the challenge lies in being able to match
3D images with the 2D records.’
Multispectral sub-dermal scanners verify identity even if the fingerprint is
covered by a latex work glove. Image courtesy of UKB International. Iris recognition
Iris recognition systems utilise the unique patterning on the iris to identify
individuals, which is formed from the first year of life and remains stable from
then on. Simon Appleton, project manager at the Liverpool company Human Recognition
Systems (HRS) in the UK, views iris recognition as being one of the most accurate
of all biometric tests. ‘Statistically, it is more accurate than DNA fingerprinting.
It’s also non-contact, as the individual simply presents their eye to the device,
which avoids problems with hygiene,’ he says.
HRS supplies systems that recognise people and their behaviours, and has been
working with the UK Department of Health to implement biometric methadone dispensers
in prisons across England. The project aims to ensure inmates receive the prescribed
dose of methadone, a drug used to treat recovering heroin addicts.
According to recent figures from the National Offender Management Service (NOMS)
responsible for the administration of correctional services in England and Wales,
approximately 83,000 offenders are housed in prisons across England and Wales
and more than half of these have some form of drug dependency problem.
Methadone is still a dangerous drug and overdoses can damage health and potentially
prove fatal. Appleton comments: ‘Manually dispensing the drug is subject to human
error and staff can also be fooled by prisoners claiming to be someone else in
order to take their prescription.’ The system supplied by HRS uses iris or fingerprint
recognition to identify the prisoner and dispense the correct dose according
to patient files stored on computer.
Work on iris recognition algorithms was pioneered by John Daugman of the University
of Cambridge Computer Laboratory, and many of today’s commercially-available
iris recognition equipment are based on this in some form.
‘The prevalence of biometrics will only accelerate as more work is carried out
and as the technology matures,’ states Lau of the University of Kentucky. ‘Iris
recognition, in particular, is greatly improving. The image quality of high-resolution
cameras is increasing to the point where, soon, cameras will be able to capture
images of people walking down the street and zoom in on the eye with sufficient
image quality as to make an accurate identification.’
HRS is currently developing iris recognition technology to do just that. ‘Current
technology is limited to the individual presenting their eyes to the device at
a distance of approximately 30cm,’ says Appleton. ‘The product under development
is still at the R&D stage, but aims to be able to make a positive identification
without the person having to stop moving.’
The use of biometrics as a method of identification is increasing and many companies
and organisations are becoming aware of the advantages of the technology. Easton
of UKB International comments: ‘Biometric technology has an application anywhere
a lock or switch needs to be operated by someone or a group – and not by others.
Basic security technology has not changed in centuries. With locks, a bolt is
either in or out. A switch is on or off. Biometrics provides a new key, unique
to the individual. A key that can never be lost, stolen, buddied, copied or hacked.’
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