Re-chained PoSt (Latency model) (better name?)

Assume the Latency model, WinningPoSt-like setting.

Assuming HDD access latency of $\tau = 17 [\textrm{ms}]$

Targeting a percentage $\alpha$ of the block time, perform $N$ iterations of the following routine:

Initial Input: interactive randomness

1. Based on randomness generate $M$ (sector, position) tuples which are challenged (assume that we have mechanism not to challenge the same drive in one iteration).
2. Fold responses to these challenges into the randomness and repeat.

We can perform $N = \frac{\alpha\cdot\textrm{block time}}{\tau}$ of such iterations while the adversary has $\textrm{block time}$ duration to regenerate $N$ iterations in sequential manner.

We use $M$ challenges in each iteration, to decrease the efficiency of the adversary storing some percentage of replicas.

Given that the adversary has $\textrm{block time}$ to regenerate $N$ sequentially, this gives that we need to ensure that the adversary cannot regenerate faster than:

If sealing takes time $t_H$ and regeneration takes time $t_A$ then the $C_L = \frac{t_H}{t_A}$

Value of $C_L$ in current PoRep is ~240 (120min to seal, 32s to regenerate).

From this we get that:

Adversary can delete $\beta$ percentage of storage (space gap) while caching $1-\beta$ of it on fast device for which we assume access latency of zero.

This result in the adversary having the chance of $1-(1-\beta)^M$of during the iteration incurring latency penalty of $t$ due to being forced to regenerate. $M$ in the range of 20-40 results in very high probabilities of forced regeneration for $\beta$ in range of 0.1-0.2.

Similar to: Untitled

Current numbers:

52k challenges, 20ms time to regenerate, M=30,

Instead of using execution extension, we use a natural delay of regeneration.

“it's fine if an adversary can regenerate a single challenge”

2018 conversation: if you are in latency model, you must assume that PoRep is free, so I regenerate all my sectors when I’m challenged.

Way to get around it: High minimum miner size, cost model element