Army signals security & "Clansmen" series radios

[Dave Howe]

> You surely could but PK is not an essential to such ad hoc 'you and you
but
> not you' encryption. an
No, but it makes life a lot easier. Possible scenarios are that you need to
distribute a single message to 'n' recipients, some of which won't have a
common key, and the list of which you won't know in advance. you may also
need a mechanism to allow keys to be changed (from either end) without
needing a separate secure channel in case of possible compromise, or an
emergency mechanism to allow point-to-point secure comms in case the link
back to base is broken.

> But traffic analysis should not help. It should detect the broadcast but
> cannot tell how many recipients there were and even less who those
recipents
> were. If you assume that the recipients must in turn transmit
> acknowledgement and that these will be detected:
An assumption here is that the Public key could have and therefore probably
has fallen into unfriendly hands; assuming they now have a mapping of Public
Key to identifiable designation, they can pull the PK outer wrapper and
identify the recipients, even if not the message content.

> Would one expect that traffic analysis is likely to help identify the
> strength, composition and location of a nuclear strike force from a
homeland
> broadcast half a world away?
Nope, that should not happen. I won't say it can't (if they are downlinked
from a satelite, unless ALL messages are automaticallly sent via all
satellites, you can assume that a recipient is somewhere inside the
footprint; ideally, that footprint should be worse than useless for
location, but sillier things than precisely-targetted transmissions have and
will happen)