The 2012 Turing award goes to two cryptography pioneers Shafi Goldwasser and Silvio Micali. I don’t do much of cryptography (for that matter I never did anything serious on that front, besides doing some C programming to demonstrate RSA and later on some class project involving elliptic curve cryptography and mathematica programming at EPFL). But I always was fascinated by the topic of Cryptography, largely for the many interesting toy like, yet deeply thought provocative combinatorial as well as probabilistic problems it addressed. Several of these problems stay at the very intersection of CS theory and cryptography.
One such classical problem that we all learned in graduate classes is the zero knowledge proof. The idea is pretty cute. In the most simple scenario, this involve two parties Alice and Bob, who don’t trust each other, but one of them (say Alice) have to convince the other (bob) that she has knowledge (say a mathematical proof) of something without really revealing it. The fact that it is not revealed explains why it is zero knowledge (Bob in the end never get to know what Alice know, but just gets convinced that she knows!). So, it will work more like an interactive protocol wherein a lot of questions are being asked by Bob, chosen randomly, depending on prior answers from Alice. Doing this way for long, can Alice convince Bob, with an overwhelmingly high probability, that she knows what was claimed? Such an interactive protocol constitute what is coined as a zero knowledge proof. An example would be a novel ATM machine where, you don’t have to enter the PIN (unlike the ones that we have), but you can still convince the machine that you know your correct PIN. Sound cool and yet thought provoking, right? Well, that is why I said it is cute and interesting. This zero knowledge interactive proof idea was first conceived by the new Turning award winners. The names didn’t strike me initially with the Turning award news, but after reading the details, it occurred to me that, I had read their classic paper , as part of my coursework at EPFL.
A bit more formally stated, the two entities are namely a Prover and a Verifier. In the ATM example, the ATM machine is a verifier and you the user is a Prover. Prover knows the proof of a mathematical statement and verifier tries to verify whether the claim is indeed correct with high probability. The machinery of zero knowledge proof is that, if the prover is trying to trick, the verifier will be able to find that out as well, with high probability. There are many examples illustrating this beautiful idea. A classic example is the problem of helping a blind man in identifying whether two otherwise identical balls are of different colors? Can you convince him, without really telling which is which? Now there are variants of their original idea and myriads of practical significance have emerged or are still emerging.
The ACM award page has pretty enthralling account of these two pioneers (Shafi and Micali). Now, here is an interesting family trivia. Shafi Goldwasser and her husband Nir Shavit together now keeps three Gödel Prize in their shelves, besides adding the Turing award aroma, now to their household!