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1inch Fusion+
About
HTLC-like cross-chain intent protocol built by 1inch.
About
HTLC-like cross-chain intent protocol built by 1inch.
HTLC-like cross-chain intent protocol built by 1inch.
Architecture
Fusion+ is an intent-based atomic swap protocol. A user signs an order for tokens on the source chain. A resolver fills it through the 1inch Limit Order Protocol, moving the user’s tokens into a deterministic source-chain escrow and supplying a safety deposit. The resolver then supplies the requested tokens and another safety deposit to a matching destination-chain escrow.
The escrows do not communicate across chains. They are linked by matching swap parameters and the hash of a secret held by the user. If the source order is never filled, no escrow is created and the user’s tokens remain in their wallet.
Settlement
After verifying the destination-chain deposit, the user reveals the secret. It releases the destination-chain tokens to the user and the source-chain tokens to the resolver. The caller of each withdrawal receives that escrow’s safety deposit. During later public periods, a Resolver Access Token (RES) holder can execute withdrawals, but cannot change their fixed token recipients.
Recovery
A standard HTLC lets each depositor reclaim their own funds after a timeout. Fusion+ does not give this right to the user who supplied the source-chain deposit. The filling resolver must cancel the source escrow to return the tokens to the user, or a RES holder can do so after a later timeout. The safety deposit rewards the caller for executing this recovery on the user’s behalf.
If neither acts, the user’s deposit can remain frozen. In the discovered Ethereum deployment, after eight days the filling resolver can rescue any remaining source-chain tokens to itself. On the destination chain, the resolver is the depositor and can cancel to recover its own tokens after the destination timeout.
Resolver access and control
Each order contains a timed resolver whitelist. A listed resolver can fill without a RES NFT once its assigned time begins. After the order’s general access time, a non-listed resolver needs an owner-issued RES NFT. The NFT also gates public withdrawals and source-chain cancellation.
The Fusion+ factory and escrow implementations are immutable. The RES NFT owner controls NFT-based resolver access and the public recovery paths, while the owner of the shared Limit Order Protocol can pause new source-chain fills.
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Ethereum
Actors:
A Multisig with 3/5 threshold.
- Can interact with FeeBank
- collect fee-token credit consumed from resolver accounts, rescue arbitrary ERC20 or native-token balances (including funds backing unused resolver credit), and transfer ownership
- Can interact with ResolverAccessToken
- choose the authorized resolver set by minting, burning or force-transferring RES tokens, authorize token mints or transfers by signature, and transfer ownership
Ethereum
Custody contract for resolver fee-token deposits. Depositing increases the resolver’s credit in the associated charger contract, while withdrawing reduces credit and returns only the still-available amount. The owner can collect credit already consumed as protocol fees and can rescue arbitrary assets held by the contract.
- Roles:
- owner: GnosisSafe
Implementation for deterministic destination-chain escrow clones. Each clone holds the taker’s destination token amount plus a native-token safety deposit. During the private withdrawal window only the taker can reveal the secret and release the tokens to the maker; during the public window an access-token holder can perform the same action. After cancellation starts, only the taker can recover the destination tokens. The caller executing a withdrawal or cancellation receives the safety deposit. After 8d, the taker can rescue any remaining token or native balance from the clone.
Fusion+ factory and 1inch Limit Order Protocol extension. A source-chain order fill calls this contract through the configured Limit Order Protocol, validates the resolver against the order’s time-dependent whitelist or access token, optionally charges the resolver fee, and deploys a deterministic EscrowSrc clone holding the maker’s tokens. On the destination chain, anyone can fund and create the matching EscrowDst clone. Partial fills use Merkle proofs so each cumulative fill is bound to a different secret hash.
Resolver Access Token (RES) used by this Fusion+ deployment. A balance of one marks an address as an authorized resolver: after an order’s configured allowed time the holder can fill it outside its time-dependent whitelist (paying a fee when enabled), and after the relevant escrow timelocks the holder can execute public withdrawals or source-chain cancellations to the predetermined recipient in exchange for the safety deposit.
- Roles:
- owner: EOA 1
Implementation for deterministic source-chain escrow clones. Each clone holds the maker’s source token amount plus a resolver-funded native-token safety deposit. During the private withdrawal window only the swap’s taker can reveal the secret and withdraw the tokens (optionally to another address); during the public window an access-token holder can do so only to the taker. After cancellation starts, the taker—or later an access-token holder—can return the tokens to the maker. The caller executing a withdrawal or cancellation receives the safety deposit. After 8d, the taker can rescue any remaining token or native balance from the clone.