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Re: one possible motivation for X.509

At 12:35 PM 7/19/96 -0500, Rik Drummond wrote:
>>I have to get that mapping over a secure channel.  If I have to go to that
>>trouble, then I can get the public key hash rather than the DN over that
>>channel and I won't have needed the DN.
>Nice discussion....Why do I need to "get the that mapping over a secure
>channel"? The point is not clear to me.....later...Rik

Thanks for the question, Rik -- nice practice for next week's talk :)

The premise we guard against with identity certificates is the one of a man
in the middle who controls *all* channels between me and my other person and
is able to impersonate that other person at will and in real time.  If you
violate those assumptions, then you've allowed a way for us to exchange
public keys.

If you keep to those assumptions, then Mallet (in the middle between Alice
and Bob) can direct Alice to the wrong DN -- one Mallet created to
impersonate Bob or one belonging to some other Bob whom Mallet paid off.

I agree that this kind of attack assumes Mallet has a huge amount of power
-- but that's the assumption under which certificates are needed in the
first place.

 - Carl

|Carl M. Ellison          cme@cybercash.com   http://www.clark.net/pub/cme |
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