From: Hugh Sasse Staff Elec Eng <hgs@...>
Date: 2003-08-07T18:49:32+09:00
Subject: Re: More on DRB & OpenSSL

On Thu, 7 Aug 2003, Nathaniel Talbott wrote:

> Hugh Sasse Staff Elec Eng [mailto:hgs@dmu.ac.uk] wrote:
>
> > I scratched together some notes at:
> >
> > http://www.eng.cse.dmu.ac.uk/~hgs/ruby/dRuby/
>
> I know, and I've been referring to it heavily. Thanks!

Thanks, nice to know it is of some use.
>
> BTW, is the RDoc on that page really for 1.3.8? Think you could update it? I
> suppose I could RDoc it myself, but I'd rather be lazy ;-)

Yes, it is for dRuby-1.3.8 [not Ruby-1.3.8! I joined the ruby
community circa 1.4.3 :-)]  Thanks for the reminder, I'll update
that.
>
>
> > I've not got into SSL with this yet, I'm using SHA1's of
> > (nonce + passwd)s to authenticate messages at the moment.
>
> Really? Can you tell me a bit more about that? Perhaps I can avoid SSL
> altogether.

It doesn't encrypt the message, but does a checksum with data that
is never transmitted.  Thus you can only forge the checksum if you
have that data, so you can trust it.  From the comments I wrote:

# A nonce is a word that is used only once (according to concise
# Oxford Dictionary.)  The purpose is that it is generated, and a
# password is added to it, and the hash of the whole string is
# generated.  Thus a hash is passed across the network so that the
# password can be checked against this hash without having to send
# the password across the network.  This is used in CRAM-MD5, see
# RFC2195 and RFC2104.  CRAM == Challenge Response Authentication
# Mechanism, MD5 is the message digest format. An Alternative to MD5
# is SHA1.

I'd rather not post my code, because of exposing weaknesses in it.
These will exist because I find cryptographic systems full of
subtleties, one of the reasons I have not got to grips with writing
SSH code.  This is slightly better, I suppose, than thinking I can
write such things and have them secure!

>
>
> Nathaniel
>
> <:((><
>
        Hugh