Neo: Limit attacks by malicious nodes

[Tommo-L]

Summary or problem description

If we are under attack, a large number of transactions are sent from a certain node. Parallel verification of transactions in Blockchain will result in fewer opportunities for other normal user transactions to be verified. https://github.com/neo-project/neo/pull/1298#issuecomment-559341882

Do you have any solution you want to propose?

Need more discussion, one simple solution is to add message frequency limitation.

Neo Version

• Neo 2
• Neo 3

Where in the software does this update applies to?

• P2P (TCP)

[lock9]

I think we need to implement weighted distribution to process messages per peer, in different queues. We could have priority nodes too, making them have a greater weight in message distribution.

[shargon]

Also, verify signatures could be expensive, we should disconnect nodes if the fail the verify of the message that he relay.

[ShawnYun]

If we use index to synchronize the blocks, we also need to consider the attack with invalid blocks.

[vncoelho]

@Tommo-L, perhaps we should focus on NEO3 only.

@shargon, agreed with that, surely we should disconnect from nodes that sent invalid signatures, I do not see a normal case that this may happen.

@ShawnYun, do you think that the metrics we mentioned on #1397 should be discussed here as well?
Agree with you as well about the index of invalid blocks.