activation: bind post data to genesis id

[dshulyak]

part of: spacemeshos/pm#135
depends on: #3505

this can be implemented independently from spacemeshos/pm#168

• initialize PostSetupManager with genesis id. when imgr.id is passed to Initiliazer and Prover prefix it with genesis id
• initialize Validator with genesis id. prefix miner id with genesis id when ValidatePost is called

@moshababo could you please review this task?

[moshababo]

Currently, gpu-post doesn't support id size other than 32 bytes. So we need to change that, or let id be the hash of genesis ID and miner ID.

Besides that, LGTM.

[lrettig]

My understanding was that POPS-VRF (spacemeshos/pm#168) would achieve this. @dshulyak is the idea here that this is a stopgap until that is done? Or do you think we need both for some reason?

[dshulyak]

the way pops-vrf described in spacemeshos/pm#168 allows to generate post data in advance. i don't recall the motivation, but i asked on the last call if we can reuse post data between networks and the answer was no.

[moshababo]

Closing in favor of spacemeshos/pm#172.