[Cryptography] List of Proven Secure Ciphers / Hashes

R. Hirschfeld ray at unipay.nl
Sun Sep 7 08:09:26 EDT 2014


> From: Jerry Leichter <leichter at lrw.com>
> Date: Fri, 5 Sep 2014 13:52:13 -0400
> 
> 
> On Sep 4, 2014, at 9:23 PM, Jonathan Katz <jkatz at cs.umd.edu> wrote:
> > Once you allow known-plaintext attacks, symmetric-key crypto is also in NP.
> This is a meaningless statement.  NP has an exact, technical definition.  There's nothing to "allow" or "disallow".

Although the OP was perhaps not very precise, I think something along
the lines of the following is meant: if S is a (polynomial-time)
symmetric encryption function, then {<x,y> | exists k: S(x,k) = y} is
in NP (just nondeterministically guess the key k and verify that the
plaintext x yields the ciphertext y).

Ray


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