Phys.Org: Cryptography without using secret keys

[coderman]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Thursday, October 17, 2019 8:00 PM, Peter Fairbrother <peter at tsto.co.uk> wrote:
> ...
> Reminds me of one of the solutions to Reagan's "Trust, but Verify"
> policy: (supposedly-) unclonable speckle patterns were painted on ICBMs
> etc, and when they wanted to make sure the ICBMs were where they were
> supposed to be the inspectors shone light on them and inspected the
> return patterns.
>
> Except the return patterns were secret - the incoming light was secretly
> chosen by the verifying party, so making forging much harder - a forger
> would either have to know the incoming light pattern and forge returns
> from those direction - perhaps possible - or have to forge a token such
> that it matched to paint from every direction, thought to be impossible.


this reminds me of another physical system:

implosion nukes (modern nukes) all use varying lengths of wire to igniters in the shaped charges surrounding the pit.

the result is that you must vary the ignition signal to each charge according to the secret lengths, otherwise you cannot achieve symmetrical implosion.

not a complete deterrent to unauthorized detonation, but certainly makes it much more difficult.


best regards,