Jacek Sieka 6b60a774e0
Lazy aggregated batch verification (#3212)
A novel optimisation for attestation and sync committee message
validation: when batching, we look for signatures of the same message
and aggregate these before batch-validating: this results in up to 60%
fewer signature verifications on a busy server, leading to a significant
reduction in CPU usage.

* increase batch size slightly which helps finding more aggregates
* add metrics for batch verification efficiency
* use simple `blsVerify` when there is only one signature to verify in
the batch, avoiding the RNG
2021-12-29 15:28:40 +01:00
..

Gossip Processing

This folder holds a collection of modules to:

  • validate raw gossip data before
    • rebroadcasting it (potentially aggregated)
    • sending it to one of the consensus object pools

Validation

Gossip validation is different from consensus verification in particular for blocks.

There are multiple consumers of validated consensus objects:

  • a ValidationResult.Accept output triggers rebroadcasting in libp2p
    • We jump into method validate(PubSub, Message) in libp2p/protocols/pubsub/pubsub.nim
    • which was called by rpcHandler(GossipSub, PubSubPeer, RPCMsg)
  • a blockValidator message enqueues the validated object to the processing queue in block_processor
    • blockQueue: AsyncQueue[BlockEntry] (shared with request_manager and sync_manager)
    • This queue is then regularly processed to be made available to the consensus object pools.
  • a xyzValidator message adds the validated object to a pool in eth2_processor
    • Attestations (unaggregated and aggregated) get collected into batches.
    • Once a threshold is exceeded or after a timeout, they get validated together using BatchCrypto.

Security concerns

As the first line of defense in Nimbus, modules must be able to handle bursts of data that may come:

  • from malicious nodes trying to DOS us
  • from long periods of non-finality, creating lots of forks, attestations