Modern cryptography is about so much more than encryption; as follows of this blog will know. Last month I discussed how the technique of secure multi-party computation (MPC) can be used to provide defence mitigation techniques for servers. By splitting up a secret held on one server into two secrets held on two servers one can mitigate against a single server being compromised by an attacker. The functionality provided by the secret is then still accessed, but via a secure multi-party computation protocol. What is surprising is that such a protocol is now really practical; whereas a few years ago it would have been inconceivable to think about implementing it.
But there are all sorts of other cool things one can do with MPC. A recent video by our Estonian friends on YouTube shows an application of MPC to the world of space. The problem statement is quite simple; there are so many man made satellites orbiting the earth that it is likely that two will collide. Given how expensive this is, in terms of replacing the satellite, people want to avoid this. However, the location of each satellite can be a closely gaurded secret; it can even be a national secret. So what we want is a way for two parties to compute whether two satellites are about to hit each other, without either party learning the location of the other satellite in the case where they are not about to hit each other (if they are going to hit each other then the location of the collision is in some sense going to leak by definition). As expected this is another practical, real world application, for multi-party computation.
So with MPC being used to stop satellites hitting each other cryptographers really are becoming rocket scientists.