[600] in cryptography@c2.net mail archive
Re: The unmentionable algorithm
daemon@ATHENA.MIT.EDU (jamesd@echeque.com)
Mon Apr 21 13:27:28 1997
From: jamesd@echeque.com
Date: Sun, 20 Apr 1997 08:12:19 +0800
To: Steven Bellovin <smb@research.att.com>, Adam Back <aba@dcs.ex.ac.uk>,
coderpunks@toad.com, cryptography@c2.net
At 09:40 PM 4/20/97 -0400, Steven Bellovin wrote:
> DES really is easy to describe. The implementation problems arise
> because we generally use languages that are too low-level. This is
> it:
>
> for i = 1 to 16
> l[i] = r[i-1]
> r[i] = l[i-1] XOR f(R[i-1], K[i])
Except of course that f is not at all easy to describe,
and you have not defined R, and you have left out some other
stuff.
> What have I left out? Nothing complex.
If your claim was true, you would not have left it out.
If I am allowed to use "high level functions" I can define any
algorithm in one line.
You can define RC4 in ordinary arithmetic operations in a few
lines.
If you try to define DES in terms of those ordinary arithmetic
operations, you will run on for about ten times as long.
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