From: Bill Stewart <stewarts@ix.netcom.com>
Date: Wed, 14 May 1997 16:21:02 +0800
To: cypherpunks@toad.com
Subject: Proxy Cryptography draft available
Message-ID: <3.0.1.32.19970514002854.0067f568@popd.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain


Matt Blaze posted the following to cryptography/coderpunks.
Looks like potentially cool stuff. I had to use 
ftp://research.att.com/dist/mab/proxy.ps
as a URL, but that may just have been Netcom DNS weirdnesses.

>Subject: Proxy Cryptography draft available
>Date: Tue, 13 May 1997 18:37:10 -0400
>From: Matt Blaze <mab@research.att.com>
>Sender: owner-cryptography@c2.net
>
>I've put a draft of a new paper in my ftp directory.  Comments and
>discussion welcome.  In particular, I'm curious if anyone can find
>any real practical application for symmetric proxy functions.
>
>ftp://ftp.research.att.com/dist/mab/proxy.ps
>
>Proxy Cryptography
>
>Matt Blaze
>Martin Strauss
>
>AT&T Labs -- Research
>{mab,mstrauss}@research.att.com
>
>Abstract:
>
>This paper introduces {\em proxy cryptography,} in which a {\em
>proxy function,} in conjunction with a public {\em proxy key,}
>converts ciphertext (messages in a public key encryption scheme or
>signatures in a digital signature scheme) for one key ($k_1$) into
>ciphertext for another ($k_2$).  Proxy keys, once generated, may
>be made public and proxy functions applied in untrusted environments.
>Various kinds of proxy functions might exist; {\em symmetric} proxy
>functions assume that the holder of $k_2$ unconditionally trusts
>the holder of $k_1$, while {\em asymmetric} proxy functions do not.
>It is not clear whether proxy functions exist for any previous
>public-key cryptosystems.  Several new public-key cryptosystems
>with symmetric proxy functions are described: an encryption scheme,
>which is at least as secure as Diffie-Hellman, an identification
>scheme, which is at least as secure as the discrete log, and a
>signature scheme derived from the identification scheme via a hash
>function.
>
>

#			Thanks;  Bill
# Bill Stewart, +1-415-442-2215 stewarts@ix.netcom.com
# You can get PGP outside the US at ftp.ox.ac.uk/pub/crypto/pgp
#     (If this is a mailing list, please Cc: me on replies.  Thanks.)