[2818] in WWW Security List Archive
Re: SSL and certificates
daemon@ATHENA.MIT.EDU (Marc Branchaud)
Tue Aug 27 12:03:09 1996
Date: Tue, 27 Aug 1996 10:09:25 -0400 (EDT)
From: Marc Branchaud <marcnarc@zoo.net>
To: trevor_sterritt@mail.amsinc.com
cc: www-security@ns2.rutgers.edu
In-Reply-To: <9607268411.AA841103340@mail.amsinc.com>
Errors-To: owner-www-security@ns2.rutgers.edu
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On Mon, 26 Aug 1996 trevor_sterritt@mail.amsinc.com wrote:
>
[ ... ]
>
> 1. The session key is not transferred securely when one party does not
> have a digital certificate. A bad guy could swipe the session key and
> "decrypt" data being transferred between the legitimate parties.
>
Actually, the DES key is transferred securely in that no third party is
able to read it. The problem is that the party without a certificate has
no guarantee about who she's talking to. That is to say, the party _with_
the certificate can be the bad guy.
The basic function of a certificate is to let you know who you're talking
to. These days, people's browsers typically store certificates, while
servers don't. So if you have a particular server's certificate in your
browser, you can be sure that you're dealing with that server (and not
some spoofer), so you can place those credit-card orders with confidence.
However, it's unlikely that the server has a certificate for you. So the
server really has no idea who it's talking to. For retail sales, this
isn't really a problem since most stores don't care who they sell to. But
when you get into intranet-type stuff, where, say, you want to securely
serve sensitive data to your employees in the field, then it matters. The
employees want to be sure that they connect with your server and your
server wants to be sure that it's only talking to your employees.
This is where a public key infrastructure (PKI) comes in. A PKI provides
a means of distributing certificates so that both parties in a
communication know who they're talking to. There are a couple of IETF PKI
initiatives. The furthest along is PKIX, based on the X.509 standard. A
newer one is SPKI, which is endeavoring to start from scratch.
Marc
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