[DIS] fiber-payjoin-kit: Collaborative Privacy for the Nervos Fiber Network
Executive Summary
As the Nervos ecosystem rolls out the Fiber Network (CKB’s native Lightning Network equivalent), establishing robust privacy and payment primitives early is critical. While Fiber enables high-throughput, low-cost off-chain payments, standard payment channels suffer from blockchain surveillance heuristics (input/output mapping).
fiber-payjoin-kit is an open-source, asynchronous Rust library that brings collaborative Payjoin privacy natively to the Nervos Fiber Network. By allowing the receiver to contribute inputs to the funding transaction of a state channel, it completely breaks the common-input ownership heuristic, ensuring off-chain CKB payments remain entirely private.
This proposal seeks a $25,000 Development Grant
Funding Request
| Component | Amount | Purpose |
|---|---|---|
| Development Grant (Phase 1) | $25,000 | Core Rust library, Fiber Network integration, CLI, and Documentation |
1. The Problem: Off-Chain Privacy Leaks
The Fiber Network is designed to scale CKB transactions. However, when users open payment channels on UTXO-based chains, blockchain analytics firms use the “common-input heuristic” to assume that all inputs in the funding transaction belong to the channel initiator. This permanently links the identities of the sender and receiver before the off-chain payment even begins.
Without protocol-level privacy primitives built into the Fiber Network SDKs early on, institutional capital and privacy-conscious users will hesitate to route significant volume through the network.
2. The Solution: Collaborative Funding (Payjoin)
fiber-payjoin-kit solves this by introducing collaborative transaction building.
Instead of the sender funding the entire Fiber channel opening themselves, the receiver also contributes input Cells to the transaction. To an outside observer on the CKB L1, the funding transaction looks like a standard multi-party coinjoin or an unrelated script execution. It becomes mathematically impossible to determine who funded the channel, who is the sender, and who is the receiver.
Key Features:
- Asynchronous Rust API: Designed to drop cleanly into existing Fiber node implementations and wallets.
- Non-Interactive Fallbacks: Seamlessly falls back to standard channel openings if the receiver’s node goes offline.
- Cell-Model Native: Optimized specifically for CKB’s UTXO and Cell-Deps architecture, avoiding the heavy computational overhead of EVM-based mixers.
3. Why Now? (The Timing)
The Nervos ecosystem is actively rolling out the Fiber Network. If robust privacy primitives are not established before significant liquidity migrates to these off-chain channels, user privacy will be permanently compromised by early blockchain surveillance indexing. Building this now ensures privacy is a native, default option from day one of the Fiber Network’s lifecycle, rather than an afterthought patched in later.
4. Why Us? (Direct Prior Work)
We are not building this from scratch. We are porting an architecture we have already successfully built.
Our team (ILE Labs) maintains the lightning-payjoin-kit—an open-source Rust library that performs this exact collaborative privacy function for the Bitcoin Lightning Network. We intimately understand the complex state-machine logic required to coordinate asynchronous, multi-party channel funding.
Furthermore, because CKB’s Cell Model is a generalized extension of Bitcoin’s UTXO model, the cryptographic and structural assumptions we solved for Bitcoin map perfectly to CKB.
5. Development Roadmap & Milestones
Note: In compliance with the CKB Community Fund DAO Rules for budgets exceeding $10,000, the initial down payment is set to 20%.
Total Budget: $25,000 USD (payable in CKB)
Initial Down Payment (20%) — $5,000
- Project kickoff, repository setup, and initial architecture mapping of the PSBT-equivalent for CKB Cells.
Milestone 1 — The Core Rust Primitive (Weeks 1-4) — $8,000
- Port the core Payjoin state-machine logic from
lightning-payjoin-kitto support CKB Cell structures. - Implement the secure passing of unsigned Cell payloads between sender and receiver.
Milestone 2 — Fiber Network Integration (Weeks 5-8) — $8,000
- Build the integration layer connecting the Payjoin library directly to the Nervos Fiber Network SDK.
- Develop the asynchronous communication protocol over the Fiber P2P layer to coordinate the collaborative funding.
Milestone 3 — CLI, Examples, and Audit (Weeks 9-10) — $4,000
- Deliver a developer CLI (
fiber-payjoin-cli) to demonstrate local testing of collaborative channel openings. - Publish comprehensive documentation and integration examples for wallet developers.
5. About the Team (ILE Labs)
We are a veteran Web3 infrastructure and Rust development team specializing in cryptography, payment primitives, and low-level execution environments.
Core Team:
- Charles Emmanuel (Blockchain Developer): GitHub (@CodexEmmzy)
- M3G47R0N / Onyekachukwu Nweke (Blockchain Developer): GitHub (@Onyekachukwu-Nweke)
- Steven Hert (Blockchain Developer): GitHub (@steven3002)
- Ayomide Oladehinde (Cryptography Researcher): Portfolio
Proof of Work:
Our GitHub (ILE Labs) contains deep, production-ready infrastructure spanning multiple ecosystems:
lightning-payjoin-kit: The exact architectural predecessor to this proposal, built in Rust for the Lightning Network.foc-devkit&mx-tx-simulator: Complex local testing environments for Filecoin and MultiversX.
We look forward to feedback from the committee and members of the Nervos ecosystem.