Comment Re:Public-Key vs. Secret-Key Crypto and P?=NP (Score 1) 165
Pick any cryptosystem (symmetric or asymmetric, except one-time pad of course). If you have a key, is it "easy" (=possible within polynomial time) to check if the key will decrypt a cipher text? Well, almost certainly, otherwise it would be a pretty impractical cryptosystem.
Disagree. It is possible to construct a CryptoFunction C(t, k) such that exists k_0 != k where D(t, k_0) = t_0 != t, with t_0 "plaintext" that appears correct but is, in fact, wrong, by inserting specifically tailored "trash" data.