---
eip: 7752
title: H3-Indexed Cross-Chain Bridge Intent
description: An interface for intent-based cross-chain asset and data bridging with H3 geospatial routing, a 1% protocol fee, and TTL-bounded intents.
author: Opacus Protocol (@bl10buer)
discussions-to: https://ethereum-magicians.org/t/erc-7752-h3-indexed-cross-chain-bridge-intent/23531
status: Draft
type: Standards Track
category: ERC
created: 2026-03-28
requires: 165
---

## Abstract

[ERC-7752](./eip-7752.md) defines an intent-based bridging protocol optimised for 0G network data availability proofs. A submitter locks a gross payment on the source chain; **1 % is immediately collected as a protocol fee**; the remaining 99 % is escrowed until a permissioned fulfiller submits a cross-chain proof. If the intent expires or is cancelled, the net amount is refunded.

## Motivation

Cross-chain bridging is plagued by fragmented interfaces, inconsistent fee models, and lack of TTL semantics. ERC-7752 proposes a minimal, composable standard that:

* **Unifies intent expression** – a single `submitIntent` covers token transfers, data payloads, and NFT bridges.
* **Integrates with 0G DA** – the `proofHash` field anchors the 0G data-availability proof receipt on-chain.
* **Enforces fee uniformity** – a hardcoded 1 % fee removes negotiation overhead and front-running surface.

## Specification

### Constants

| Name | Value | Description |
|---|---|---|
| `BRIDGE_FEE_BPS` | `100` | Protocol fee in basis points (1 %) |

> **Note:** The address that receives the protocol fee (`feeRecipient`) is implementation-defined. Implementations MUST make `feeRecipient` configurable and MUST NOT hardcode a chain-specific address.

### Enums

```solidity
enum IntentStatus { Pending, Fulfilled, Cancelled, Failed, Expired }
enum IntentType   { TokenTransfer, DataPayload, NFTBridge }
```

### Structs

```solidity
struct BridgeIntent {
    address     submitter;
    IntentType  intentType;
    bytes       payload;
    uint64      sourceChainId;
    uint64      destChainId;
    address     token;
    uint256     grossAmount;
    uint256     feeAmount;
    uint256     netAmount;
    bytes32     proofHash;
    IntentStatus status;
    uint64      createdAt;
    uint64      fulfilledAt;
    uint64      expiresAt;
}
```

### Methods

#### `submitIntent`

```solidity
function submitIntent(
    IntentType intentType,
    bytes calldata payload,
    uint64 destChainId,
    uint64 ttlSeconds,
    address token,
    uint256 gross
) external payable returns (bytes32 intentId);
```

MUST compute `feeAmount = (gross * BRIDGE_FEE_BPS) / 10_000` and forward to the implementation-defined fee recipient atomically.  
MUST set `expiresAt = block.timestamp + ttlSeconds`.  
MUST emit `IntentSubmitted(intentId, submitter, destChainId, feeAmount)`.

#### `fulfillIntent`

```solidity
function fulfillIntent(bytes32 intentId, bytes32 proofHash) external;
```

MUST only be callable by a registered fulfiller.  
MUST revert if `block.timestamp > intent.expiresAt`.  
MUST release `netAmount` to fulfiller.  
MUST emit `IntentFulfilled(intentId, fulfiller, proofHash)`.

#### `cancelIntent`

```solidity
function cancelIntent(bytes32 intentId) external;
```

MUST only be callable by `intent.submitter`.  
MUST refund `netAmount` to submitter (fee is non-refundable).  
MUST emit `IntentCancelled(intentId, submitter)`.

#### `setFulfiller`

```solidity
function setFulfiller(address fulfiller, bool allowed) external;
```

MUST only be callable by contract owner. Manages trusted fulfiller set.

### Events

```solidity
event IntentSubmitted(bytes32 indexed intentId, address indexed submitter, uint64 destChainId, uint256 feeAmount);
event IntentFulfilled(bytes32 indexed intentId, address indexed fulfiller, bytes32 proofHash);
event IntentCancelled(bytes32 indexed intentId, address indexed submitter);
event IntentFailed   (bytes32 indexed intentId, bytes reason);
```

### [ERC-165](./eip-165.md)

Compliant contracts MUST implement `IERC7752` and MUST return `true` from `supportsInterface` for `type(IERC7752).interfaceId`.

## Rationale

* **TTL-bounded intents** – prevents capital lock indefinitely; enables solver competition.
* **Permissioned fulfillers** – a whitelist prevents griefing while the permissionless fulfiller model matures.
* **0G DA anchoring** – `proofHash` stores the DA proof CID, enabling on-chain verification of data availability.

## Backwards Compatibility

No existing bridge standard (LayerZero, Hyperlane, Axelar) is modified. ERC-7752 is composable as a transport layer above existing messaging protocols.

## Reference Implementation

See `contracts/ERC7752ZeroGBridge.sol` in the Opacus-Standart repository.

## Security Considerations

* **Fulfiller trust** – The whitelist is a centralisation risk; future versions should integrate decentralised solver auctions.
* **Reorg safety** – Fulfillers MUST wait for sufficient source-chain confirmations before calling `fulfillIntent`.
* **Fee finality** – Fees are forwarded immediately; a fee-on-settlement model should be considered for high-value transfers.

## Copyright

Copyright and related rights waived via [CC0](../LICENSE.md).