From: Andrew.Spring@ping.be (Andrew Spring)
Date: Tue, 25 Jul 95 09:59:21 PDT
To: cypherpunks@toad.com
Subject: Re: big word listing
Message-ID: <v01510103ac39a90b698b@[193.74.217.8]>
MIME-Version: 1.0
Content-Type: text/plain


>
>Instead of that, send H(pid,clock,hostname,H(password)) to the server, for
>some hash function H().  Then the server only needs to keep H(password)
>around, rather than the plain password.  This is similar to current
>systems, except the plain password isn't sent across the network.
>
>H() can be whatever you fancy; 25 crypts, MD5, SHA-1, etc.  Of course,
>I'm sure this is far from being a new idea...

Keeping H(password) on the server and logging in with H(blob,H(password)) is
no different than keeping the password on the server and logging in with
H(blob,password).  Anyone who can read the password file on the server can
authenticate himself.

To protect against packet sniffers monitoring your login stream _and_
system crackers looking at the password file, you need some form of PKC.

Free-after-1997 example:
        g is a generator of a prime p.

        password is X (0<X<p);

        password file has g^X mod p.

        login server generates Y, issues challenge g^Y.
        expected response is g^XY mod p

        login client has X, generates (g^Y)^X = g^XY mod p.

        J. Random SuperHacker can get g^X, and g^Y, but not g^XY.

Free-after-2000 example.
        Server Has RSA Public Key
        Client has Private Key.

        Server generates challenge.

        Client signs [Hash of] challenge.



--
Thank you VERY much!  You'll be getting a Handsome Simulfax Copy of your
OWN words in the mail soon (and My Reply).
<Andrew.Spring@ping.be> PGP Print: 0529 C9AF 613E 9E49  378E 54CD E232 DF96
   Thank you for question, exit left to Funway.