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YoumuChan | 1 year ago

We don't even know the complexity class of factorization or discrete log, yet we still use those problems in DH, RSA, ECDSA, ...

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eru|1 year ago

All of those problems are known to be in NP and co-NP. In that sense, we know some complexity classes they belong to.

However, we don't know if these bounds are tight, or whether they are eg in P, or something in between.

keepamovin|1 year ago

We don't know that factorization is NP-complete> Show me a reduction from SAT to factorization.

It's kind of trivial to say it's in NP because we can verify in P time, that's not a criticism of you just of the definition!!

I think a better definition of NP is "only nonpoly algos can exist, no P algos can exist". By that definition of NP, we don't even know that it's in NP strictly because there could exist P algorithms for solving it. It's more in 'unknown-NP' if that were a class! hahaha! :)

openasocket|1 year ago

I always found that part odd. I’d assume you would want the problem you build your crypto system built around to be NP-complete, since that would seem to put you on the firmest possible ground. And yet those are most likely not NP-complete, and I think the post-quantum systems proposed aren’t NP complete either.

Maybe being NP-complete isn’t as important as I realize? Or maybe there’s something about NP-complete problems that make them less amenable to be a valid crypto system?