Q&A On Face-Recognition
September 2, 2003
Q&A On Face-Recognition
What is facial recognition technology?
Facial recognition systems are built on computer programs that analyze
images of human faces for the purpose of identifying them. The
programs take a facial image, measure characteristics such as the
distance between the eyes, the length of the nose, and the angle of
the jaw, and create a unique file called a "template." Using
templates, the software then compares that image with another image
and produces a score that measures how similar the images are to each
other. Typical sources of images for use in facial recognition include
video camera signals and pre-existing photos such as those in driver's
license databases.
How is facial recognition technology currently being used?
Unlike other biometric systems, facial recognition can be used for
general surveillance, usually in combination with public video
cameras. There have been three such uses of face-recognition in the
U.S. so far. The first is in airports, where they have been proposed -
and in a few cases adopted - in the wake of the terrorist attacks of
September 11. Airports that have announced adoption of the technology
include Logan Airport in Boston, T.F. Green Airport in Providence,
R.I., and San Francisco International Airport and the Fresno Airport
in California.
A second use of the technology was at the 2001 Super Bowl in Tampa,
where pictures were taken of every attendee as they entered the
stadium through the turnstiles and compared against a database of some
undisclosed kind. The authorities would not say who was in that
database, but the software did flag 19 individuals. The police
indicated that some of those were false alarms, and no one flagged by
the system was anything more than a petty criminal such as a ticket
scalper. Press reports indicate that New Orleans authorities are
considering using it again at the 2002 Super Bowl.
The technology has also been deployed by a part of Tampa, Ybor City,
which has trained cameras on busy public sidewalks in the hopes of
spotting criminals. As with the Super Bowl, it is unclear what
criteria were used for including photos in the database. The operators
have not yet caught any criminals. In addition, in England, where
public, police-operated video cameras are widespread, the town of
Newham has also experimented with the technology.
How well does facial recognition work?
Computers can do increasingly amazing things, but they are not magic.
If human beings often can't identify the subject of a photograph, why
should computers be able to do it any more reliably? The human brain
is highly adapted for recognizing faces - infants, for example,
remember faces better than other patterns, and prefer to look at them
over other patterns. The human brain is also far better than computers
at compensating for changes in lighting and angle. The fact is that
faces are highly complex patterns that often differ in only subtle
ways, and that it can be impossible for man or machine to match images
when there are differences in lighting, camera, or camera angle, let
alone changes in the appearance of the face itself.
Not surprisingly, government studies of face-recognition software have
found high rates of both "false positives" (wrongly matching innocent
people with photos in the database) and "false negatives" (not
catching people even when their photo is in the database). One problem
is that unlike our fingerprints or irises, our faces do not stay the
same over time. These systems are easily tripped up by changes in
hairstyle, facial hair, or body weight, by simple disguises, and by
the effects of aging.
A study by the government's National Institute of Standards and
Technology (NIST), for example, found false-negative rates for
face-recognition verification of 43 percent using photos of subjects
taken just 18 months earlier, for example. And those photos were taken
in perfect conditions, significant because facial recognition software
is terrible at handling changes in lighting or camera angle or images
with busy backgrounds. The NIST study also found that a change of 45
degrees in the camera angle rendered the software useless. The
technology works best under tightly controlled conditions, when the
subject is starting directly into the camera under bright lights -
although another study by the Department of Defense found high error
rates even in those ideal conditions. Grainy, dated video
surveillance photographs of the type likely to be on file for
suspected terrorists would be of very little use.
Simlilar results have been found with real-world face-recognition
trials. A study based on police documents obtained by the ACLU (PDF)
shows that a face-recognition system deployed on the streets of Tampa,
Florida failed to identify a single suspect from the database, and had
many false alarms.
In addition, questions have been raised about how well the software
works on dark-skinned people, whose features may not appear clearly on
lenses optimized for light-skinned people.
Samir Nanavati of the International Biometric Group, a consulting
firm, sums it up: "You could expect a surveillance system using
biometrics to capture a very, very small percentage of known criminals
in a given database."(See article)
What is the government's previous experience with facial recognition?
Several government agencies have abandoned facial-recognition systems
after finding they did not work as advertised, including the
Immigration and Naturalization Service, which experimented with using
the technology to identify people in cars at the Mexico-U.S. border.
However, the government also has possession of a huge, ready-made
facial image database - driver's license photos - and is looking into
how they can be used. By law, the government can't sell those photos
to private companies, but there are no prohibitions on their use for
surveillance purposes by the government itself. The Federal government
has begun to fund pilot projects on expanding the use of driver's
license photos to facial recognition databases.
Should we deploy face-recognition in airports to prevent terrorism?
It makes no sense to use face-recognition in airports. To begin with,
there is no photo database of terrorists. Only two of the 19 hijackers
on September 11 were known to the CIA and FBI - and surviving
terrorists aren't exactly lining up to have their photo taken by the
U.S. government. In addition, the technology simply isn't reliable
enough for such an important security application. It would work
especially poorly in the frenetic environment of an airport, where
fast-moving crowds and busy background images would further reduce its
already limited effectiveness. The evidence suggests that these
systems would miss a high proportion of suspects included in the photo
database, and flag huge numbers of innocent people - lessening
vigilance, wasting precious manpower resources, and creating a false
sense of security.
Should we use the technology in other public places?
If facial recognition is unjustified in airports and at public events
such as the Super Bowl, its use for general surveillance is even more
inappropriate. The security threat on a public street is far lower
than in airports, and sociological studies of closed-circuit
television monitoring of public places in Britain have shown that it
has not reduced crime. The balance between the risks and benefits of
facial recognition is even more unfavorable in such locations than in
airports.
How does facial recognition technology threaten privacy?
One threat is the fact that facial recognition, in combination with
wider use of video surveillance, would be likely to grow increasingly
invasive over time. Once installed, this kind of a surveillance system
rarely remains confined to its original purpose. New ways of using it
suggest themselves, the authorities or operators find them to be an
irresistible expansion of their power, and citizens' privacy suffers
another blow. Ultimately, the threat is that widespread surveillance
will change the character, feel, and quality of American life.
Another problem is the threat of abuse. The use of facial recognition
in public places like airports depends on widespread video monitoring,
an intrusive form of surveillance that can record in graphic detail
personal and private behavior. And experience tells us that video
monitoring will be misused. Video camera systems are operated by
humans, after all, who bring to the job all their existing prejudices
and biases. In Great Britain, for example, which has experimented with
the widespread installation of closed circuit video cameras in public
places, camera operators have been found to focus disproportionately
on people of color, and the mostly male operators frequently focus
voyeuristically on women.
While video surveillance by the police isn't as widespread in the
U.S., an investigation by the Detroit Free Press (and followup) shows
the kind of abuses that can happen. Looking at how a database
available to Michigan law enforcement was used, the newspaper found
that officers had used it to help their friends or themselves stalk
women, threaten motorists, track estranged spouses - even to
intimidate political opponents. The unavoidable truth is that the
more people who have access to a database, the more likely that there
will be abuse.
Facial recognition is especially subject to abuse because it can be
used in a passive way that doesn't require the knowledge, consent, or
participation of the subject. It's possible to put a camera up
anywhere and train it on people; modern cameras can easily view faces
from over 100 yards away. People act differently when they are being
watched, and have the right to know if their movements and identities
are being captured.
The bottom line: how do we decide whether to install facial recognition systems?
Facial recognition - or any security technology - should not be
deployed until two questions are answered. First, is the technology
effective? Does it significantly increase our safety and security? If
the answer is no, then further discussion is beside the point. If the
answer is yes, then it must be asked whether the technology violates
the appropriate balance between security and liberty. In fact, facial
recognition fails on both counts: because it doesn't work reliably, it
won't significantly protect our security - but it would pose a
significant threat to our privacy.
YOU CAN FIND MORE ON:
http://news.com.com/2100-1023-275313.html?legacy=cnet
http://www.vnunet.com/vnunet/news/2144460/face-recognition-mobiles
http://www.epic.org/privacy/facerecognition/ |
