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add section on digital signatures

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William Banfield
2021-09-14 09:53:59 -04:00
parent 7ae27cb856
commit 660b6833e9
1 changed files with 24 additions and 1 deletions
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docs/rfc/rfc-003-performance-questions.md
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@@ -209,7 +209,28 @@ valuable and impactful.
### Digital Signatures
// TODO: (@wbanfield)
#### Verification
Working with cryptographic signatures can be computationally expensive. The cosmos
hub uses [ed25519 signatures][hub-signature]. The library performing signature
verification in Tendermint on votes is [benchmarked][ed25519-bench] to be able to perform an `ed25519`
signature in 75μs on a decently fast CPU. A validator in the Cosmos Hub performs
3 sets of verifications on the signatures of the other 139 validators in the Hub
in a consensus round, during block verification, when verifying the prevotes, and
when verifying the precommits. With no batching, this would be roughly `3ms` per
round. It is quite unlikely, therefore, that this accounts for any serious amount
of the ~7 seconds of block time per height in the Hub.
#### Use in gossip protocol
Currently, Tendermint's digital signature verification requires that all validators
receive all vote messages. Each validator must receive the complete digital signature
along with the vote message that it corresponds to. This means that all N validators
must receive messages from at least 2/3 of the other N-1 validators in each consensus
round. Given the potential for oddly shaped network topologies and the expected
variable network roundtrip times of a few hundred milliseconds in a blockchain,
it is highly likely that this amount of gossiping is leading to a significant amount
of the slowdown in the Cosmos Hub and in Tendermint consensus.
### Tendermint Event System
@@ -224,3 +245,5 @@ valuable and impactful.
[issue-1319]: https://github.com/tendermint/tendermint/issues/1319
[abci-commit-description]: https://github.com/tendermint/spec/blob/master/spec/abci/apps.md#commit
[abci-local-client-code]: https://github.com/tendermint/tendermint/blob/511bd3eb7f037855a793a27ff4c53c12f085b570/abci/client/local_client.go#L84
[hub-signature]: https://github.com/cosmos/gaia/blob/0ecb6ed8a244d835807f1ced49217d54a9ca2070/docs/resources/genesis.md#consensus-parameters
[ed25519-bench]: https://github.com/oasisprotocol/curve25519-voi/blob/d2e7fc59fe38c18ca990c84c4186cba2cc45b1f9/PERFORMANCE.md