Retrieval limits in the Symmetric PoRep model

Creator

Nicola

Created

Oct 26, 2023 12:31 AM

There are limits to the speed or cost of retrieval in the symmetric PoRep.

Limits in the cost model

• A realistic cost ratio (Amax) between the honest setup and the attacker setup is ~10x.
• A realistic time of a challenge window is ~6hrs (recall that the cost model requires challenging every sector)
• Assuming that sealing is as efficient as a regeneration attack

→ Theoretical minimum: The cost of unsealing must be AT LEAST the cost of 60hrs (2 days and a half) worth of storage costs, at today’s storage costs it is $0.06 to retrieve 1 TiB (at 0.025 TiB/day)

→ Current costs For context, SDR cost per GB is (0.04 per sector / 32) is $0.00125, which would account for 10% of the S3 cost.

For comparison

• S3 Archival expidite access costs ~$0.01/GB, so in this setting, the unsealing cost of $0.00006/GB will not have a major impact on costs.
• From DigitalOcean current costs are at $0.0003/GiB

Request:

Limits in the time model

• A realistic latency ratio (Amax) between the honest setup and the attacker setup is ~5x.
• A realistic time for replying to a challenge to a reliable, secure and distributed protocol (e.g. a timestamp service) is ~200ms
• Assuming that sealing is as efficient as a regeneration attack

→ The time to unseal must be AT LEAST 1s (5x200ms)

Due to inefficiencies between sealing and regeneration attacks (today they are in the order of 20-50x!), we must multiply those numbers by another factor - optimistically another 5-10x.