Secure Computation

Suppose your university department is about to make a job offer, and a friend tells you that their department is also about to make an offer. Are you entering into a bidding war, or are the two departments interested in different people? You open your mouth to ask, “Are you making an offer to X?” then shut it, imagining an answer of, “Actually, we were interested in someone else, but now that you’ve told me that X is available...” Your friend is similarly closed-mouthed. You are at an impasse. You both want to find out if you are interested in the same person, but you don’t want to reveal anything beyond this one bit of information. What can you do? This problem, and many others like it, makes simultaneous demands on the privacy and usability of sensitive data that go beyond the capabilities of conventional cryptography. Encrypting sensitive data is analogous to placing jewels in a safe. While in the safe, the jewels are protected from theft, but you can’t wear them to the ball. Conventionally encrypted data may be safe from prying eyes, but until it is decrypted it can’t be used, even by legitimate parties for agreed upon purposes.