[Cryptography] Update on the Mesh, cute threshold scheme.

[Jonathan Thornburg]

On Tue, Sep 21, 2021 at 12:37:38PM -0400, Phillip Hallam-Baker wrote:
> The expiry agent publishes a series of public keys that expire daily,
> weekly, monthly, yearly etc. Daily keys for the next three years, weekly
> for the next ten, after that monthly, and so on. Maybe 10,000 in all.
> 
> Forget the internal mechanism for a moment, assume its threshold with
> Shamir/Lagrange stuff goin' on. Point is that the service will perform a
> key exchange up to the predetermined expiry date/time. At some point after
> the expiry date/time it will physically erase the keying material
> completely.

But what do you do about the NSA having acquired a copy of the expiry
agent's private keys via a secret-to-everyone-except-one-expiry-agent-VP
"national security letter"?  It seems to me that as soon as any 3rd party
(e.g., the expiry agent) has information -- *particularly* high-value
keying material -- you have to assume that $GOVERNMENT can get a copy.