Karl Denninger <[EMAIL PROTECTED]> writes:
> On Tue, Mar 07, 2000 at 12:23:33AM +0100, Jan Meijer wrote:
> > Hi Karl,
> >
> > Whilst taking the risk to look like someone from Microshot, Netscape or the
> > others some comment on your pleads for clarity.
> >
> > > There are to separate things that secure web servers do.
> > >
> > > 1. Authenticate who you're talking to, so that when you engage in
> > > commerce you have some indication that the merchant you think you're
> > > dealing with is really who you're dealing with.
> > >
> > > 2. Encrypt the data so that it cannot be intercepted between the
> > > sending and receiving machines.
> >
> > True. Crypto allows for two other quite basic functions: non-repudiation
> > and integrity. You only mentioned authenticity and confendiatlity.
>
> Well, confidentiality implies integrity, in that a tampered data stream
> won't decode. Public key crypto with a known certification on the public
> key provides non-repudiation (assuming the private key has not been
> compromised)
This is absolutely not true.
Consider a data stream enciphered with RC4. It's perfectly
easy to undetectably flip any plaintext bit by
flipping the corresponding ciphertext bit. If you know the
plaintext, you can modify it predictably.
> The "man in the middle" risk is a red herring. As long as the CA vouches
> for the key exchange its "cool", and you'd only detect the man in the middle
> attack if you actually LOOKED at each certificate for each page served.
>
> How many people click on the padlock and LOOK at each page's certificate?
> Without a warning nobody checks - and as such the risk is still there.
This is incorrect. The browser has automatic checks that
the certificate matches the server's domain name. These
checks aren't perfect, but they're not useless either.
If these checks didn't exist then it would be necessary to check
every certificate manually. That would be bad.
-Ekr
--
[Eric Rescorla [EMAIL PROTECTED]]
PureTLS - free SSLv3/TLS software for Java
http://www.rtfm.com/puretls/
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