A Lay Explanation of the MIT Research Paper "Carnival Booth: An Algorithm for Defeating the Computer-Assisted Passenger Screening System"

By Russell L. Brand.

Imagine a world where you knew who all the terrorists were in advance.  It is a much simpler world than the one we have.  There would be no waiting in airport security lines.

While we don't have that, some people think we are in a world where we know who the terrorists ARE NOT.  And in that world, we can avoid searching the people we know are safe and devote all (or most of) our effort just to the people we aren't sure of.  It sounds good.  Some of us avoid being hassled and the system moves faster for everyone.

BUT...

What if we are occasionally wrong?  Just a few of these SEEMINGLY SAFE people are really terrorists.  They'd slip by with us good upstanding citizens.

And what if the terrorist organizations sent all their folks on a few test trips?  After a few trips, they would know which ones got searched each time and which ones never got searched.  Then they would use the ones that had never gotten searched on their mission, knowing that these SEEMINGLY SAFE people (who were really terrorists) could more easily get onto the planes.

Unfortunately, the efforts to target our searching attention, rather than better protecting us and more efficiently using our resources, instead telegraphs what we know and allows the bad guys to have a better chance of outmaneuvering us.

While the intuition of this is easy to understand, it took a team of leading mathematicians at MIT to prove that it is true and to show that there are no simple fixes to the targeted approach.  And the implications of their findings cannot be ignored.

It is critically important to not let a terrorist know whether or not he is a suspect until the moment we capture him.  And unfortunately, that means long lines for us all.