Cryptography

Yael Tauman Kalai’s breakthroughs secure the digital world, from cloud computing to our quantum future.

My master’s thesis was titled “How to Leak a Secret.” Here’s the problem: We know how to digitally sign — to say, “This is me that wrote this message.” But say I want to sign something as an MIT professor, but I don’t want people to know it’s me? That way the secret does hold some water because you know an MIT professor signed it, but you don’t know who.

We solved this with something we called ring signatures, which were inspired by a notion in computer science called witness-indistinguishable proofs. Let’s say there’s a statement and two different ways to prove it. We say there’s two “witnesses” to the statement being correct — each of the proofs. A witness-indistinguishable proof looks the same no matter which you use: It hides which witness you started with.