Slashdot Mirror
Biometric Face Recognition Exploit
clscott writes "A researcher
at the U. of Ottawa has developed an exploit to which most
biometric systems are probably vulnerable.
He developed an algorithm which allows a fairly high
quality image of a person to be regenerated from a
face recognition template. Three commercial face rec.
algorithms were tested and in all cases the image could
masquerade to the algorithm as the target person.
Here are links to a
talk
and a
paper.
Unfortunately, biometric templates are currently considered
to be non-identifiable, much like a password hash.
This means that
legislation gets passed to require
hundreds of millions of people to have their biometrics
encoded onto their passports. This kind of vulnerability
could mean that anyone who reads these documents has access
to the holders fingerprint, iris images, etc."
the point that EVERYbody is missing is that biometric authentication is inherently flawed - it's like a password that cannot be changed. Obviously there are innumerable flaws. How is this news?
Anyone who has done work on computer vision would have guessed this to be so. What would interest me is in how it would be possible to exploit the algorithms, i.e., how bad of a picture can you get away with? Certain images that might not look anything like a face to you or me will quite possibly be able to fool the system.
The passport angle is probably a red herring though. The unreliability of photo identification is already known. Identity theft is simple and easy. Hell, here in New Mexico, we've already been the first state to accept 'Matricula Consular' cards as valid ID for driver's licenses. Matricula Consular cards, of course, are given out by Mexican embassies to undocumented Mexicans living in the US. By 'undocumented,' I mean illegal, of course. Check out the immigration reform site www.vdare.com for some more information on the subject.
You don't understand what the article is talking about. When you enroll in a biometric system, the system itself -doesn't- match based on your picture, but on a 'template' which is created by taking your standard data and performing certain destructive operations to arrive to a much smaller 'template' which can still be used to identify you.
This is very similar to the one-way hashing that happens with unix passwords, only that in this case the hashing is 'lossier' so you have 'confidence scores' instead of a black/white answer.
The article shows that given this 'hashed' value you can recreate an image that has a good chance of not only being authenticated by the same system/algorithm (which already should be very hard, given the one-way nature of the templatization) =BUT= also by different systems!
It also is really interesting how if you have access to the 'confidence score' outputted by the recognizer, you can take arbitrary images and blending/averaging them again come up with an image that works.
This is definitely not useless news and will have quite some implications.
-- the cake is a lie
This isn't such a big deal for face recognition systems, because face recognition systems suck at identifying people anyway. Why? First a little tereminology:
With any biometric matcher you have to define a match "tolerance", which defines how close a pair of templates (usually one from a database and one from a livescan) have to be before they're considered to be a match. Set this tolerance too "loose" and you get lots of false positives (matches that shouldn't match), set it too "tight" and you get the opposite, false negatives. The tolerance setting where you get roughly the same number of errors each way is called the equal error point, and the error rate is called the equal error rate (abbreviated ERR for some unfathomable reason).
Well, all current face recognition systems have an ERR that is too high to be useful in nearly any situation, even when used for identity verification, as opposed to the much-harder problem of identification (verification: I say I'm Bill Gates, and the system agrees; identification: The system says I'm Bill Gates, not RMS or anyone else). It's possible that in the future this will change, of course.
However, this doesn't really matter because we already have ready access to an excellent and very widely available face recognition system: the Mark I eyeball. Millions of years of evolution have made people extremely good at identifying and matching human faces. What people aren't so good at (with notable exceptions) is matching a face against a database of thousands of faces they've seen only once, and *that* is something that face recognition systems can do extremely well. They may not be able to decide which faces are a "match", but they can do an excellent job of finding the *closest* faces, which can then be reviewed by the super-duper face-matching algorithm contained in the average person's head.
When automated face recognition is used in that sort of context, spoofs like this one are unlikely to be very useful; if you want to impersonate someone you'd better get a face that's good enough to fool another human. It's doable, certainly, but much harder. And holding a laptop screen in front of your face is likely to raise some suspicions.
Note to ACs: I usually delete AC replies without reading them. If you want to talk to me, log in.
The algorithm they used is simple. They use the face recognition
system as "oracle" and present different images until the match
is achieved. The different images are not chosen at random, but
rather evolutionary. That is, a selection of images is presented,
and the best (highest score) is chosen. Recursively, new selections
are derived from the best image, and again presented to the oracle.
According to the article 24,000 images are necessary to achieve
convergence, when the initial images were specifically chosen to
NOT be visually similar to the "target" image.
Some oracles can't be questionned 24,000 times - eg at an airport
or an ATM machine. You might become arrested long before finished.
However, often press releases indicate which company designed the
software for a particular implentation of face recognition. You
can easily purchase other software of the same company (or find
an OEM product) and thus have the same (or very similar) oracle
on your desk at home. There you can do the 24,000 iterations to
get ahold of the "good" image and then proceed to remodel your
face or whatever way you intend to "present" the image to the
real face recognition system.
In my opinion, biometrics just doesn't work for security. Because
everyone is open to see the datasets.
Just look at those stupid press releases of Siemens/Infineon, who
make high-payed security engineers invent ATM cards with finger
print sensors. Owners finger print => money from ATM. Where does
owner leave his finger print, when handling the card? Couldn't be
on the very ATM card, possibly?
Acceptable security requires
a) something you have, and
b) something you know.
When the item you have is stolen, the thief lacks the information
you know. And vice-versa, when the secret is learned (eg shoulder
surfing at ATM), the item you have still misses to complete the
electronic robbery.
Biometrics is something you have, not something you know. That is
the key thing to learn here!
It can be copied, without your noticing, but that doesn't make it
category b). It still is something you have, because everybody has
access to it when he's physically near to you. You can't just shut
up to make it stay secret.
Therefore, biometrics won't (ever) work as long as it's coupled with
other category a) stuff. A biometric dataset can possibly replace a
physical token, but it can NOT replace a PIN code.
I'm happy that this is once again demonstrated, with press coverage.
Marc
This is even easier to compromise than having a keycard or something, as the individual could at least hide it somewhere. They CAN'T hide their face without