Re: making public keys public

["L. McCarthy" <lmccarth@ducie.cs.umass.edu>]

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Eric Hughes writes:
> >  If you're not going to make the public key public, why use public key
> >  cryptography at all ?  Save time and effort and use a symmetric cipher.
> 
> You can't do authentication with a shared secret key, because there's
> nothing to differentiate the two sides of the link.

Is it really important to distinguish the two sides ?  The additional threat
is that an attacker could spoof my correspondent to me, once she's grabbed my
secret key. But a) I thought we were assuming that other people being spoofed
is _their_ problem, not ours, and b) if she's nabbed my key, odds are she's
hacked my account anyway, leaving me with much larger problems.

> In addition, a closely held public key might be held by 10 people;

Hmm, `closely-held' suggests that the `public' key is being passed around
as a secret over some channels, in which case it might as well be
a secret key being passed around over those channels to the 10 people.

> with secret keys there are 90 different private keys instances to
> manage.

Wouldn't there only be 45 ?  I agree that this is quite a few, but it's a
reasonable tradeoff between disk space and processing speed unless you're
communicating with a large number of people.

- - -L. Futplex McCarthy; PGP key by finger or server  "We've got computers, 
we're tapping phone lines; I know that that ain't allowed" --Talking Heads

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