[14759] in cryptography@c2.net mail archive
Re: A-B-a-b encryption
daemon@ATHENA.MIT.EDU (David Ross)
Sun Nov 16 18:27:19 2003
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Sun, 16 Nov 2003 18:43:11 +0000
From: David Ross <David.Ross@uq.net.au>
Reply-To: David.Ross@member.sage-au.org.au
To: martin f krafft <madduck@madduck.net>
Cc: crypto list <cryptography@metzdowd.com>
In-Reply-To: <20031114081925.GA11764@piper.madduck.net>
martin f krafft wrote:
> it came up lately in a discussion, and I couldn't put a name to it:
> a means to use symmetric crypto without exchanging keys:
>
> - Alice encrypts M with key A and sends it to Bob
> - Bob encrypts A(M) with key B and sends it to Alice
> - Alice decrypts B(A(M)) with key A, leaving B(M), sends it to Bob
"Decrypting" B(A(M)) with key A will typically result in another
encryption: a(B(A(M))), not B(M). The operations are not associative,
commutative or distributive, so this will not work.
> - Bob decrypts B(M) with key B leaving him with M.
Rgds,
- Dave.
---------------------------------------------------------------------
The Cryptography Mailing List
Unsubscribe by sending "unsubscribe cryptography" to majordomo@metzdowd.com
