Army signals security & "Clansmen" series radios

[David Howe]

> I think the reason may be that public key systems are good for
> one-to-one and one-to-few communications (and I would be surprised
> if the military did not use them for that). But they are not a good
> solution to communications that have to be broadcast to many recipients
> (to all Her Majesty's ships, for example).
That preassumes one key==one recipient. there is no real reason you can't
have a hierarchy of keys - one per ship, one per flotilla, one per taskforce
transmitted using the more granular keys when the taskforce is set up. You
can then factor in your groupings by using the largest possible key that
doesn't contain a non-recipient (so, you could send to two flotillas, and to
three ships that aren't in a flotilla that is effected but should know
anyhow)
The downside is traffic analysis - if you suddenly notice three ships and
two flotillas getting shared encypted traffic, you might start looking for
connections. however, if you lose the key material on a given ship, you
compromise (at worst) the groupings that ship is a member of, not the navy
as a whole.