go-waku-light

Note: This uses a temporal go-waku branch

This repo contains a proof of concept for a waku light client, integrating RLNv2 + onchain trees. It allows to create RLN zk-proofs without having to synchronize the membership Merkle tree. It achieves so by getting the Merkle proof required to generate the zk RLN proof directly from the smart contract, included upstream here.

And end to end integration can be done by creating a new network using this modified contract deployed in the Polygon zkEVM. We create two nodes.

node1

docker run -p 60000:60000 quay.io/wakuorg/nwaku-pr:2770-rln-v2 --pubsub-topic=/waku/2/rs/100/0 --relay=true --lightpush=true --cluster-id=100 --rln-relay-dynamic=true --rln-relay=true --rln-relay-eth-client-address=https://rpc.cardona.zkevm-rpc.com --rln-relay-eth-contract-address=0x1ae47AAb605E3639cA88ce8F6183C3035Eb60c62 --nodekey=fa900509b7da6211dc91715260dba7431457d51cc1bb0732a58eb84ec812de99 --log-level=TRACE

And node2. Note that we use TRACE to verify that the message arrived correctly.

docker run -p 60001:60001 --network host quay.io/wakuorg/nwaku-pr:2770-rln-v2 --pubsub-topic=/waku/2/rs/100/0 --relay=true --lightpush=true --cluster-id=100 --rln-relay-dynamic=true --rln-relay=true --rln-relay-eth-client-address=https://rpc.cardona.zkevm-rpc.com --rln-relay-eth-contract-address=0x1ae47AAb605E3639cA88ce8F6183C3035Eb60c62 --log-level=TRACE --staticnode=/ip4/127.0.0.1/tcp/60000/p2p/16Uiu2HAkxTGJRgkCxgMDH4A4QBvw3q462BRkVJaPF5KQWkc1t4cp --ports-shift=1

A go-waku-light can run as follows. It publishes a message every message-every-secs being stateless, generating RLN proofs using the Merkle Proofs provided by the contract. The membership is automatically registered at startup, providing a valid priv-key.

./go-waku-light send-messages-loop \
--priv-key=SOME_PRIV_KEY \
--user-message-limit=5 \
--message="light client sending a rln message" \
--content-topic=/basic2/1/test/proto \
--pubsub-topic=/waku/2/rs/100/0 \
--cluster-id=100 \
--lightpush-peer=/ip4/127.0.0.1/tcp/60000/p2p/16Uiu2HAkxTGJRgkCxgMDH4A4QBvw3q462BRkVJaPF5KQWkc1t4cp \
--message-every-secs=5

See docs for other commands, useful for debugging.

Explanation

• Faster sync time. Uses GetCommitments instead of fetching events.
• Getting the Merkle root directly from the contract. No need to sync the whole tree.
• Getting the Merkle proof for any leaf directly from the contract. No need to sync the whole tree.

For context, RLN is a decentralized rate-limiting protocol, that allows setting a limit on the number of messages sent by each entity, using zero-knowledge proofs. Said proofs prove that i) the member is whitelisted, without revealing its index, and ii) no more than 1 message is sent every epoch, which prevents double signaling.

The main motivation is to showcase how this modification can help light clients become lighter. It makes proof generation and verification easier:

• Proof verification: Only requires the Merkle root, which is now available on-chain and can be fetched with a simple call. Before, one had to sync the whole Merkle tree with emitted events, and keep a local copy of it.
• Proof generation: Generating an RLN proof requires the Merkle proof of the leaf generating it. With this modification, said Merkle proof can be obtained directly from the contract.

Usage

Build:

go build

Listen for new memberships and Merkle root changes. You can leave this running in another terminal.

./main listen

Register a new membership. You must provide a valid Polygon zkEVM account, see faucet. Your membership information will be stored in a .json file.

./main register --priv-key=REPLACE_YOUR_PRIV_KEY

Fetches and logs the latest Merkle root and Merkle proof of the tree, using the contract as a source. Set leaf-index to your leaf index.

./main onchain-root
./main onchain-merkle-proof --leaf-index=1

Syncs the Merkle tree from the contract creating a local tree. The chunk-size indicates how many memberships are fetched at once. If too big, the RPC provider may error. Merkle proof can be locally computed, provide your leaf-index. Both onchain and local results should match.

./main local-root --chunk-size=500
./main local-merkle-proof --chunk-size=500 --leaf-index=1

Generates the RLN proof using a given membership, see the previous step. The proof is stored in a .json file. Message and epoch are hardcoded for simplicity. Note that the RLN can be generated onchain (which doesn't require to locally sync the tree since it uses the contract) and local (which syncs the tree locally).

./main onchain-generate-rln-proof --membership-file=membership_xxx.json
./main local-generate-rln-proof --membership-file=membership_xxx.json --chunk-size=500

Any RLN proof can be verified against the smart contract Merkle root.

./main verify-rln-proof --proof-file=proof_xxx.json

Advanced

The contract/contract.go can be updated if the abi is changed as follows:

git clone https://github.com/ethereum/go-ethereum.git
cd go-ethereum
go build ./cmd/abigen
./abigen --abi=../go-waku-light/contract/abi.abi --pkg=contract --out=../go-waku-light/contract/contract.go