plausibly deniable

[Robert J. Hansen]

On 7/25/10 10:10 PM, vedaal at nym.hush.com wrote:
> so, if you saw a signed message with this key, you would think it 
> would be signed by either Smith or Jones

This is not really plausible deniability.  "You say you didn't write it?
 Fine.  I guess we'll prosecute both you /and/ Jones, then!"

Let's say SmithJones at aol.com gets involved in something the authorities
don't like -- let's say narcotics trafficking.  What happens is Smith
and Jones *both* face charges of conspiracy to traffic, since the
collusion before to produce a shared keypair is prima facie evidence of
cooperation to hinder prosecution.

Is it rebuttable?  Sure.  Is it a nightmare for both of them?  Yes.
Does it make their communications plausibly deniable?  Not even close.