> Maybe you have some formal algorithm for social discovery that you haven't presented here, but without that, it's quite difficult to speculate how it would play out.

However, this process is already important when choosing software in the first place, or when updating software. Even when using PoW, every new entrant to the network needs to do some kind of social discovery to figure out which software to download in the first place. And even with PoS, people that have been regularly connected to the network do not need any social discovery. With PoS, there is an additional kind of user that an attacker can force to need to do social discovery: users who were at one point part of the network but have been offline for a long period of time. My conjecture is that this set of users is quite small in comparison to either the set of new entrants or the set of nodes who have been online frequently enough to not need any social discovery.

Would you agree that if that set of users is small enough, the difference might be insignificant? Eg would increasing the number of users that have to do some kind of social discovery by 1% be acceptable?

> My gut feel is that no, it's not sufficiently decentralized

I would tend to agree that the process of finding the right sofware is generally not decentralized enough - too easy for people to find bad software or virus ridden downloads. The only thing that saves us is that the vast majority of humanity isn't malicious.

> something like a PGP web of trust[1] could make this more reliable

I think there are a lot of things we could do like that. We have a long way to go towards actually making good computer security accessible to a significant fraction of people. First step is operating systems - or maybe even hardware.

> you're not proposing an automated way to bootstrap trust OR consensus here

Correct. What I'm proposing is a way to verify with confidence if the data (checkpoint) you received is very likely valid in cases where you're not being attacked, and a way to alert the user when an attack might be happening. The trust / social discovery part of things is basically out of scope - but already exists in its own haphazard individualized way.

> You did claim earlier that all PoS implementations have elapsed time between blocks, and I'm still mystified as to how you're claiming this is enforced.

Well I meant that the timestamps that blocks have are enforced. The actual time they're created can't be enforced. But to elaborate, in VPoS, every UTXO gets one chance per second to mint a block. Nodes will know well in advance whether or not they can mint a block or not (although other nodes can't know which peers will get that chance until that peer actually broadcasts a block). However, a node will reject blocks with a timestamp greater than its clock. Furthermore, a "difficulty" adjustment happens similar to bitcoin. X blocks per minute are targetted on average, and if 2X blocks/minute are minted in a given time range, the "difficulty" will increase until only X blocks/minute are minted. Basically, if a number C of coins has 2 chances in 10,000 of minting a block, if the difficulty doubles, that number of coins then has 1 chance in 10,000. This is how its ensured that blocks are, on average, minted some target time apart.

With a quorum based system like Casper, each quorum is allowed to mint a particular number of blocks, probably with timestamp constraints as well. And the quorums themselves must change after a specific number of blocks. I assume some similar difficulty-like adjustment is done to keep these timed properly, so that both quorums and blocks are maintained at a cadence.

Is this what you mean, or are you talking about something else?