From: "Perry E. Metzger" <pmetzger@lehman.com>
Date: Wed, 13 Oct 93 07:36:40 PDT
To: cypherpunks@toad.com
Subject: Re: Breaking DES
In-Reply-To: <9310130416.AA25367@netcom5.netcom.com>
Message-ID: <9310131433.AA06289@snark.lehman.com>
MIME-Version: 1.0
Content-Type: text/plain



Doug Merritt says:
> pmetzger@lehman.com said:
> >Each DES block is eight bytes. You can't use hashing -- the idea is
> >nonsense in context. Did you read the original post?
> 
> Yes, I did. If hashing doesn't work, you'll have to say why not.

> It's a technique that works in most other situations.

You don't know anything about hashing, then.

When I use a hash table, it is never a substitute for storing the
actual value of the thing I'm hashing. Its always just a way of
rapidly FINDING the underlying object. I have to store the underlying
object in order to compare to it. As an example, in a hashed symbol
table, I store the actual symbols.

If you tried to work out your proposed cracking algorithm instead of
requesting that other people do all your thinking for you, you'd see
what was wrong with it. 

> >Second of all, the method is still impractical. I was merely
> >giving the easiest and most obvious attack on it.
> 
> Impractical? Your response to Karl implied that it was *impossible*.

The two are very similar in our field. Cracking RSA with a 2000 bit
key is merely impractical, not impossible, where "impractical" is
defined as completely beyond human ability.

> Clearly you are preparing to drop the argument because you sense that
> your tactic of flaming didn't work.

You can lead a horse to water, but you can't make him think.

Perry