[12567] in cryptography@c2.net mail archive
Re: AES-128 keys unique for fixed plaintext/ciphertext pair?
daemon@ATHENA.MIT.EDU (Dave Howe)
Mon Feb 24 12:18:53 2003
X-Original-To: cryptography@wasabisystems.com
X-Original-To: cryptography@wasabisystems.com
From: "Dave Howe" <DaveHowe@gmx.co.uk>
To: <cryptography@wasabisystems.com>
Date: Sat, 22 Feb 2003 00:25:09 -0000
Hmm. another simpler theory to remove Shannon from the discussion.
assume that the original assertion is correct - that for each plaintext p
and each cyphertext c there exists only one key k that is valid to map
encrypt(p,k)=c. In this case, for each possible cyphertext c, *every*
possible plaintext p is a valid translation given a unique key k. for that
reason, the uniary distance for encrypt() must be larger than one block - as
it is self evidently not possible to map *any* c to a unique p without
knowledge of the key.
For that reason, Shannon cannot be applied to a single block of encrypt(),
and can be safely ignored :)
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