Suzaku Relayer Network

The Suzaku Relayer Network (SuzakuRN) is a Suzaku Sovereign Network that supercharges the Avalanche Warp Messaging (opens in a new tab) protocol with critical properties: censorship resistance, liveness, and validity.

Avalanche Warp Messaging Primer

Protocol overview

Avalanche Warp Messaging (opens in a new tab) enables trustless cross-chain communications between Avalanche networks without relying on any trusted third party. AWM is an efficient protocol that verifies message integrity using cryptographic signatures from validators of the origin chain. While off-chain relayers are needed to transfer messages from the source chain to the destination chain, they cannot submit invalid messages (that the source chain did not sign).

AWM vs IBC

AWM and IBC (Inter-Blockchain Communication Protocol (opens in a new tab)) used in the Cosmos (opens in a new tab) ecosystem, are both trustless protocols relying on verifiable proofs without needing to trust the messages relayer.

AWM differs in architecture as it does not require light clients on both ends of the connection. Connecting Avalanche L1s is streamlined since AWM is integrated within Avalanche Network Clients (ANCs). This integration is facilitated because all Avalanche validator nodes utilize the P-Chain (opens in a new tab) as a registry for their public signing keys, enabling validators from any chain to verify signatures generated on other network chains.

AWM limitations

Subject to censorship: if 2 networks rely on a limited number of entities to relay messages between their chains, these entities could collude to censor messages (permanently or temporarily, e.g. to increase MEV profit) or be subject to outages, with the same outcome for users.
Subject to hacks: Warp messages rely on validator BLS keys for signing. If an attacker successfully compromises a sufficient number of keys from a small Avalanche source chain, they could forge cross-chain messages that do not correspond to genuine on-chain state transitions. Since the destination chain validates these messages solely based on the public BLS keys registered on the P-Chain, such fraudulent messages would be accepted, potentially leading to unintended actions (e.g. unlock bridged assets) and disruptions within the ecosystem.
Difficult to incentivize: AWM relayers pay gas fees on the destination chain to deliver messages. Therefore, they require an incentive to relay messages. Teleporter (opens in a new tab), the EVM-compatible overlay on top of AWM, allows to attach a bounty to each message, that the relayer can claim after successful message delivery. Yet, the gas fees to be paid on the destination chain often require another token than the relayer incentive. This implies that relayers have the burden of (i) constantly calculating if messages are worth relaying and (ii) constantly rebalancing gas tokens between chains.

SuzakuRN

To address these limitations, the Suzaku Relayer Network relies on a decentralized set of relayers to maximize liveness, eliminate censorship, simplify incentive schemes, and reduce the attack surface for messages from small networks.

Liveness and censorship-resistance

The primary goal of SuzakuRN is to enforce censorship resistance upon AWM relayers, by:

Ensuring liveness: we make sure that each route between two Avalanche chains has a sufficient number of allocated relayers operated by different entities.
Penalizing bad-behaving relayers: each relayer has to stake an amount of $SUZ to join SuzakuRN. Each message detected by the network is attributed to a group of relayers. If a relayer repeatedly fails to deliver messages in time, its stake will be slashed.

Notary service

To protect against hacks due to BLS key leakage (see above), Avalanche chains can opt-in to the Suzaku Notary service, where the Suzaku Relayer Network will act as a circuit breaker, only relaying messages that:

Result from valid state transitions on the source chain
Do not conflict with the previously relayed messages (in the case of double signing)

For more detailed information about the concept of notary, see this post (opens in a new tab) by Aaron Buchwald, Software engineer at Ava Labs.

Simplified incentive schemes

SuzakuRN allows Avalanche L1s to simplify the incentive schemes used to reward relayers:

The L1 team subsidizes the relaying gas fees on its chain, removing (i) the need for relayers to perform complex computations to make sure that relaying a message is worth it
The L1 team pays a fixed fee per message relayed to their chain. The fees can be paid in $SUZ,$ AVAX, or $USDC, and they are in any case converted to$ SUZ before being redistributed to relayers.
Relayers are rewarded in a single currency: $SUZ (the Suzaku token)

A nice side effect of this incentive scheme is that users will only pay gas on the source L1 upon bridging.