For a fleeting moment, Mohamed Atta appeared on an airport security camera minutes before he boarded one of the planes which crashed into the World Trade Center on Sept. 11, 2001.
Was there any way the camera or its operator would have been able to identify Atta as a suspect before he hijacked and flew the first of two planes into the twin towers?
Israelis Michael and Alex Bronstein think they have the answer.
The computer whiz-kids -- 22-year-old identical twins almost impossible to tell apart -- have applied a new technology to recognizing faces in a way that may yet revolutionize international security.
"I said it to them as a joke: If you succeed in building a system that can distinguish between the two of you, you'll get (a grade of) 100," the twins' professor, Ron Kimmel of the Technion Institute in Haifa, told Reuters.
"They succeeded and got 100. They are brilliant."
The technology scans and maps the human face as a three-dimensional surface, providing a far more accurate reference for identifying a person than current systems, most of which rely on two-dimensional images, Kimmel said.
The product can potentially meet a wide range of security needs in a world shaken by the Sept. 11 attacks and a series of bombings blamed on Osama bin Laden (news - web sites)'s al Qaeda network, of which Atta was a suspected member.
Kimmel and one of his former pupils, Assi Elad, had already developed the algorithms used as building-blocks for the face-recognition system. The Bronstein twins constructed a 3-D scanner, together with engineer Eyal Gordon, and applied the ideas to face recognition.
The twins and Kimmel say they want to turn the technology -- registered for a patent in the United States -- into a commercial product, with applications ranging from airports and border crossings to security zones and teller machines.
"We have a prototype and we saw the idea works," Michael Bronstein said. "There is a hope that this will become a commercial product and allow all of us to feel more secure."
UNIQUE FACIAL SIGNATURE
The technology records the surface of a person's face by scanning it with a series of light patterns and stores the data as a three-dimensional image in a computer.
Employing mathematical algorithms similar to those used in Internet searches, the computer measures the distances between a number of sample points on the facial surface.
The distances are then reconfigured as straight lines in a three-dimensional space, creating a new and abstracted image, or signature, of a human face built on precise mathematical calculations.
Kimmel and the Bronsteins say that this signature is more or less unique to a particular person.
The advantage of the system is its ability to compare facial structures as they appear in different poses or light conditions, variables which could distort a face seen as a two-dimensional image.
"One of my students calls it sculpting in numbers," said Kimmel. "This kind of mapping makes it all invariant, or it is not influenced by our expressions. If we smile a little bit or we change our face a little, it will still be mapped into the same signature, the same kind of surface."
The system could be employed at airports or border crossings where a 3-D security camera could scan passengers' faces and compare them with a database of three-dimensional pictures of suspected criminals or terrorists, the twins said.
The technology would not work with existing two-dimensional images of suspects.
Facial signatures could also be embedded in credit cards or entry permits. People withdrawing money from an automated teller machine or seeking access to a secure compound could have their identity verified by an on-site camera.
A facial signature would be effective as a means of identification for about the same number of years as a passport photograph.
Aging, cosmetic surgery, significant changes to facial surfaces such as growing or removing a beard could disrupt the matching process.
The Bronstein twins know first hand the importance of face recognition. During the interview with Reuters, even Kimmel confused the young men, who share the same lanky build, wispy brown hair and steel-rimmed glasses.
The twins immigrated to Israel from Russia in 1991 and say they have always shared the same interests. As adults, Alex and Michael frequently complete each other's sentences and begin statements with "we" even when speaking on their own.
"We always studied the same things and it was always connected to science, if sometimes indirectly," said Alex.
Michael added: "We started working on explosives at a very young age, when we were about 8 years old, and it lasted until we were about 13 when we built a bomb that was so powerful, we were scared of it ourselves.
"So we swore that we would stop that and as a reward, Mom and Dad bought us an aquarium with fish."
The face-recognition project was assigned in a computer science course the twins took with Kimmel at the Technion, where they are studying for a masters' degree in electrical engineering.
Asked if there was any way to distinguish between them, except for Michael's shorter haircut, Alex said: "I must say that I've got a girlfriend." Michael chimed in: "We don't share those."