Decrease block time threshold

[shargon]

Summary
Currently the threshold for PrepareRequest is 10 minutes, if a malicious CN propuse a block that come from the near future (10 minutes more), it will be accepted. Next blocks will be proposed by the others trusted CN from the future too

neo/neo/Consensus/ConsensusContext.cs

Line 286 in f1d6434

Block.Timestamp = Math.Max(TimeProvider.Current.UtcNow.ToTimestampMS(), PrevHeader.Timestamp + 1);

So next round, this malicious CN could propose another block, and step by step move the chain to the future

For 7 CN this should be the scenario (CN1 malicious one):

First round:

• CN-1 (Real Time 00:00:00 , BlockTime 00:10:00)
• CN-2 (Real Time 00:00:15 , BlockTime 00:10:01)
• CN-3 (Real Time 00:00:30 , BlockTime 00:10:02)
• CN-4 (Real Time 00:00:45 , BlockTime 00:10:03)
• CN-5 (Real Time 00:01:00 , BlockTime 00:10:04)
• CN-6 (Real Time 00:01:15 , BlockTime 00:10:05)
• CN-7 (Real Time 00:01:30 , BlockTime 00:10:06)

Second round

• CN-1 (Real Time 00:01:45 , BlockTime 00:20:06)

Do you have any solution you want to propose?
Reduce the threshold to 1 or 2 minutes.

Where in the software does this update applies to?

• Consensus

[shargon]

Maybe the formula should be related to the number of verificators and the time per block, what do you think? @neo-project/core @neo-project/ngd-shanghai @erikzhang

[vncoelho]

@shargon, for me this is expected. Not a bug.

If this happens, NEO holders should vote against.

[shargon]

A malicious CN can send the chain to 2020 in 2019, this is not expected.

If this happens, NEO holders should vote against.

Vote is not a solution, the protocol must protect the network if is possible.

[lock9]

Isn't this one kind of metric that we can use to judge node health?
This can be one metric, and time that he was the speaker and did not submit a block on time can also be a metric. What do you guys think?

I agree that we should not let nodes create blocks too much in the future.

[shargon]

But what do you propose, watch and monitoring the CN in order to force a vote if this happens?