[ticker-dev] ticker-3.0 spec - Replace on Message ID

[David Arnold]

-->"Ian" == Ian Lister <ilister at dstc.edu.au> writes:

  >> using keys could ensure that the replacement message was
  >> authentic, but this is separate from the replacement mechanism
  >> itself, i think?

  Ian> I don't think the key model is suitable for doing this. (Read:
  Ian> I can't think how you'd do this without some very bad tradeoff,
  Ian> and even then only really by putting stuff in the notification
  Ian> too).

what i meant, and i'm not sure from you mail whether you disagree,
was:

a) replacement and use of keys is orthogonal.

b) if you choose to use keys, you can be as confident of the
   authenticity of a replacement message as you can of the
   authenticity of the original message.

i was not proposing any new keying mechanism.

  Ian> The problem is that you need to verify that the sender of the
  Ian> two messages has the same identity

i don't believe that's necessarily true.  

you *might* care about the sender's identity, but i think having the
same level of confidence in the authenicity of the messages
(regardless of the sender's identity or senders' identities) would
normally be sufficient.


  Ian> sending a public key as part of the first message and a
  Ian> signature with the same key as part of the second message. I
  Ian> can't see people implementing this any time soon :-)

me either.  i can't see most people caring enough.





d