Cross-chain bridge audit
Bridges hold the largest balances and have lost the most money.
What it is
A bridge is two or more systems that must agree about events neither can observe directly. The contracts are the easy part. The security lives in how a message is proved, who is trusted to attest to it, and what happens when those parties disagree or go offline.
We review both ends and the trust model between them, because a bridge is only as sound as its weakest chain.
What we examine
- Message format and replay protection across every supported chain.
- Proof verification: light clients, merkle proofs, signature schemes, optimistic windows.
- Validator and relayer sets: thresholds, rotation, and the cost of colluding.
- Mint and burn accounting reconciled across chains, including on reorgs.
- Liveness failures: what happens when relayers stop or a chain halts.
- Fee and gas handling on the destination chain, a recurring source of stuck funds.
- Emergency powers: who can pause which side, and what that strands.
What you get
Findings across both sides plus the off-chain components between them.
A written trust model: exactly who must be honest for the bridge to hold.
Failure analysis for reorgs, halts and relayer outages.
A re-audit of your fixes, included.
How the engagement runs
- 01
Scope
Chains, message types, proof system and operator set. Fixed quote.
- 02
Model
The trust assumptions written down explicitly, which often surprises the team.
- 03
Review
Both sides, the relayers and the accounting, tested against reorgs and halts.
- 04
Report
Findings with proof of concept, then verification of your fixes.
What we cover
Languages
- Solidity
- Vyper
- Rust
- Move
- Cairo
- Go
- TypeScript
- Huff
- Yul
Chains
- Ethereum
- Solana
- BNB Chain
- Polygon
- Avalanche
- Arbitrum
- Base
- TRON
- Optimism
- Cardano
- Polkadot
- Cosmos
- NEAR
- Aptos
- Sui
- TON
- Hedera
- Algorand
- Stellar
- Starknet
- ZKsync Era
- Linea
- Sei
- Sonic
- Scroll
- Mantle
- Injective
- Cronos
- Celo
- Gnosis
- Fantom
- Kaia
- Ronin
- Immutable
- Blast
- Berachain
- Monad
- Hyperliquid EVM
- Stacks
- Rootstock
- Kava
- Osmosis
- MultiversX
- Conflux
- Telos
- Theta
- Chiliz
- XDC Network
- Filecoin FVM
- Ontology
- WEMIX
- Fuel
- Taiko
- Polygon zkEVM
- BOB
- Fraxtal
- Mode
- ZetaChain
- Metis
- Manta Pacific
- IOTA EVM
- Neo X
- Unichain
- World Chain
- Soneium
- Abstract
- Ink
- Movement
- Plume
- Etherlink
- EOS
- Flow
- Zilliqa
- Harmony
- Moonbeam
- Astar
- Aurora
Not listed? Ask. If it runs smart contracts, we almost certainly review it.
Questions we get asked
Do you audit the chains the bridge connects?
Not by default. We audit your bridge and state the assumptions it makes about each chain. Where an assumption is unsafe for a specific chain, that is a finding.
What about the off-chain relayers?
In scope, and usually where the interesting findings are. Contracts get reviewed; the relayer infrastructure often has not been.
Is a bridge audit more expensive than a protocol audit?
Usually, because there are at least two execution environments plus the infrastructure between them. The scoping call gives you the fixed number.
Often bought with
Web3 and protocol audit
Line-by-line review of contracts, chain layer and upgrade paths, with proof-of-concept for every finding.
L1 and L2 infrastructure audit
Consensus, client code, validator economics, sequencers and proof systems.
Monitoring and incident retainer
Continuous on-chain monitoring with automated response, and a team on call when something moves.
Tell us what you are building and when you launch. Fixed quote in 48 hours.
Get a fixed quote