It isn't certain that you'd be able to tell WHICH input that the attacker used, at least not with my scheme where you hide who's using what input. Revealing who's using what input might not be optimal if a user want to use inputs already tied to himself AND some inputs that aren't already, and doesn't want the unlinked ones to become linked to him.
Send all inputs to one key first.
I don't see how that solves anything. You just openly linked your own inputs together yourself, then.
Someone previously proposed using Secure Multiparty Computing before to implement CJ, but one must realise that SMC is only a set of tools. E.Z.Yang proposed one specific implementation using sorting, which is a cool idea, but according to Yang himself is currently not feasible in practice. In his own words, "The big obstacle is that secure multiparty sorting is somewhat difficult to implement with large keys (since integer comparison operations tend to only handle a few bits at a time)." The hunt is still on to find an efficient way to use SMC to solve the problem.
I am quite excited that people are working on making this work and will be trying the programs proposed here when I can.
I am quite excited that people are working on making this work and will be trying the programs proposed here when I can.
General SMC/MPC (myself I usually abbreviate it as SMPC) does exist. But it seems to be less efficient than specific ones like for sorting. I am eagerly waiting for efficient general SMPC to become usable for average joes.
