eth-lightclient-rs

A crate for working with Ethereum beacon chain light client protocol messages. no_std friendly!

!! For hacking and experimentation only. This is NOT production ready code !!

This can be used to deserialize and inspect SSZ encoded SyncCommitteePeriodUpdate messages that are retrieved from a full node RPC. It can also be used to verify a transition between two adjacent sync period updates is valid using check_sync_committee_period_update.

Usage

SSZ encoded SyncCommitteePeriodUpdates can be deserialized using the try_from with a byte slice.

use eth_lightclient::SyncCommitteePeriodUpdate;

const BYTES: &[u8] = include_bytes!(
    "../tests/sync-updates/0xe4c2cee3a9455c2b7c0449152a8c7e1a7b811353e4ea2c1dbe1cbe0c790b45f7"
);

let update = SyncCommitteePeriodUpdate::try_from(BYTES);

Adjacent period updates can be verified given a chain validators root. This checks that:

• The second update has enough signatures
• The signatures are from the committee defined in the prior update
• The next sync committee proof is valid with respect to the finalized block root
• .. some other stuff

From a trusted finalized block root and committee in one sync period this allows proving that a new committee and finalized block root in the next sync period can also be trusted. This allows a light client to jump to a new trusted block root every sync period.

use eth_lightclient::{
    SyncCommitteePeriodUpdate, H256,
    check_sync_committee_period_update,
    constants::mainnet::VALIDATORS_ROOT,
};

const A: &[u8] = include_bytes!(
    "../tests/sync-updates/0xe4c2cee3a9455c2b7c0449152a8c7e1a7b811353e4ea2c1dbe1cbe0c790b45f7"
);
const B: &[u8] = include_bytes!(
    "../tests/sync-updates/0x78ae69239826edd5ac0abfe3a69e916e7479ad44e834e35a08e4df7601732a85"
);

check_sync_committee_period_update(
    SyncCommitteePeriodUpdate::try_from(A).unwrap(),
    SyncCommitteePeriodUpdate::try_from(B).unwrap(),
    H256(VALIDATORS_ROOT),
) // returns Ok(())

Authors

• Willem Olding (ChainSafe Systems)
• Eric Tu (ChainSafe Systems)
• Cayman Nava (ChainSafe Systems)

Acknowledgements

This crate was developed as part of the EthBogota hackathon for the project Zipline. Zipline is a trustless Eth beacon chain to EVM bridge that uses the beacon chain protocol.

Credit to the original authors of the sync period verification - Snowfork. Their original implementation was tightly coupled to the Substrate ecosystem and not useable outside of that context hence the refactor.