[Br0x] Non-Custodial Bridgeless Swaps: Cardano ↔ EVM

[Proposal setup] Proposal title

Please provide your proposal title

[Br0x] Non-Custodial Bridgeless Swaps: Cardano ↔ EVM

[Proposal Summary] Budget Information

Enter the amount of funding you are requesting in ADA

93400

[Proposal Summary] Time

Please specify how many months you expect your project to last

8

[Proposal Summary] Translation Information

Please indicate if your proposal has been auto-translated

No

Original Language

en

[Proposal Summary] Problem Statement

What is the problem you want to solve?

Cross-chain swaps today mostly rely on bridges or centralized relayers → high fees, custody risk, fragmented liquidity, and complex UX.

[Proposal Summary] Supporting Documentation

Supporting links

• https://br0x.vercel.app/
,
• https://sang-4.gitbook.io/br0x/about-br0x-swap/intros
,
• https://github.com/MinhSang1508/BR0x

[Proposal Summary] Project Dependencies

Does your project have any dependencies on other organizations, technical or otherwise?

No

Describe any dependencies or write 'No dependencies'

No dependencies

[Proposal Summary] Project Open Source

Will your project's outputs be fully open source?

Yes

Please provide details on the intellectual property (IP) status of your project outputs, including whether they will be released as open source or retained under another licence.

Apache 2.0 license

[Theme Selection] Theme

Please choose the most relevant theme and tag related to the outcomes of your proposal

DeFi

[Campaign Category] Category Questions

Describe what makes your idea innovative compared to what has been previously launched in the market (whether by you or others).

Our solution enables bridgeless, non-custodial swaps between Cardano (eUTxO) and EVM chains, removing wrapped tokens, centralized relayers, and custody risks. Unlike past funded projects relying on bridges, we use native lock scripts, EVM lock contracts, and Wanchain’s XFlows PoC for secure, direct swaps with simple UX, scalable backend, and multi-chain liquidity integration.

Describe what your prototype or MVP will demonstrate, and where it can be accessed.

The MVP will show a working swap interface on testnet where users connect Cardano & EVM wallets, choose assets, execute swaps, and view history in real time. It will demonstrate core bridging logic, lock/unlock flows, and liquidity routing. Accessible via a public testnet link with onboarding docs for community testing before mainnet launch.

Describe realistic measures of success, ideally with on-chain metrics.

Success Criteria (Testnet POC)

• 90% of retail users complete swap without dev help.
• Refund works in timeout cases.
• Micro-swap fee ≤ 2% (via Hydra batch).
• UI shows full trace (source tx, proof, dest tx).
• Verified end-to-end Cardano → EVM swap.

[Your Project and Solution] Solution

Please describe your proposed solution and how it addresses the problem

Current state:

• Today, most cross-chain swaps rely on bridges or centralized relayers. These methods expose users to high fees, custody risks, and repeated security incidents such as bridge hacks.
• They also fragment liquidity and create a complex, unreliable user experience.

Goal:

• This project aims to enable direct, non-custodial swaps between Cardano’s eUTxO model and EVM chains — without bridges, wrapped tokens, or intermediaries.
• The design ensures atomic execution (swap or refund), while keeping the process simple, transparent, and secure for end users.

The primary objective is to deliver an interactive prototype of the bridgeless swap app that includes all screens, user flows, transaction states, and deposit address verification.

Alongside the prototype, a minimal smart contract integration with Wanchain’s testnet will be implemented to demonstrate an end-to-end Cardano ↔ EVM swap.

Figure 1: Br0x homepage

App Interface Scope

1. Main User Flows

• Landing / Token Pair Selection – choose swap pair, enter amount, view price quote.
• Deposit Address Screen – display address and QR code with backend-signed proof, chain/token warnings.
• Progress Tracking – visual timeline: Deposit detected → Confirmations → Proof relay → Swap execution → Complete.
• Refund Request Screen – refund button available after timeout with clear instructions.
• Settings & Info – display estimated fees, allow path selection (Hydra or Wanchain).

Figure 2: Br0x navigation flow

Figure 3: Swap Configuration

Figure 4: Direct swap

2. UX Features

• Signed Deposit Quote Display – show hash and backend signature so users can verify authenticity.
• Step-by-step Warnings – preflight checks before copying deposit address.
• Live Explorer Links – clickable links to view transactions on-chain.
• Adaptive Path Recommendation – suggest Hydra for small trades, Wanchain for larger trades.

3. Prototype Tools

• Figma or Framer for wireframes and interactive mockups.
• React (Next.js) for the interactive prototype running on testnet.
• TailwindCSS + shadcn/ui for consistent UI components.

Minimal Smart Contract Scope

Cardano side

• Hold funds at a script address with datum containing token, amount, destination chain, and timeout.
• Allow refunds after timeout.
• Accept settlement trigger from proof relay (mocked or real from Wanchain testnet).

EVM side (Solidity)

• Receive proof (mocked or real) from Wanchain.
• Perform a simple swap on a test DEX (mock router).
• Send resulting tokens to the recipient.

Cross-chain messaging

• Use Wanchain testnet for the message layer (TSS proof).
• Payload format: CBOR + BLAKE2b hash, consistent across both chains.

Technical Challenges

• Interoperability: eUTxO ↔ account-based, payload mapping.
• Finality & Proof: Verification of TSS proofs.
• Atomicity: Ensure both sides succeed or refund.
• Liquidity Routing: Integrate multiple DEXes/aggregators.
• Plutus Complexity: Datum/redeemer encoding, refund logic, external triggers.

UX Challenges

• Wallet-less Flow: Direct deposits with phishing protection.
• Error Prevention: Preflight checks for wrong chain/token.
• Status Tracking: Clear timeline + explorer links.
• Refund Clarity: Visible conditions and timing.
• Cost Visibility: Show fees and best routes.

Risks

• Relayer/validator compromise.
• User errors → fund loss.
• MEV/slippage on destination chain.
• Privacy leaks from deposit addresses.
• Legal/AML compliance risks for partners.

Development Focus

The project will focus on delivering a complete user interface covering all interaction flows, designed in Figma as an interactive and responsive web prototype. This will be followed by the development of an interactive web application on testnet, powered by a state machine, mock API, and integrated live explorer links for on-chain transparency.

On the smart contract side, we will implement a minimal integration of Plutus (Cardano) and Solidity (EVM) along with a relay mechanism. The final stage will showcase an end-to-end swap demo on testnet, serving as a proof of concept with Wanchain relay to validate the feasibility of the solution.

[Your Project and Solution] Impact

Please define the positive impact your project will have on the wider Cardano community

Phase 1 is more than just planning — it is the strategic ignition point for positioning Cardano at the center of a new wave of decentralized cross-chain interoperability. This stage delivers the groundwork for a seamless, secure, and user-friendly asset bridge that allows Cardano to connect effortlessly with EVM-based blockchains and beyond.

By focusing on deep market research, architectural design, and an intuitive user flow, Phase 1 ensures that the final solution not only leverages Cardano’s technical strengths — low transaction costs, high throughput, and sustainable consensus — but also presents them in a way that any user, regardless of their blockchain experience, can interact with confidently.

This early stage sets the tone for the entire project’s success by:

• Expanding Cardano’s liquidity horizons — enabling users and liquidity providers from other chains to interact with the Cardano ecosystem without friction.
• Boosting network activity and adoption — the improved user experience will lower onboarding barriers, increasing daily active users and transaction volume.
• Strengthening Cardano’s position in DeFi innovation — showing that Cardano is not just a settlement layer but an active player in secure, decentralized, and privacy-conscious financial infrastructure.
• Creating a foundation for long-term scalability — designing a system that can adapt to future protocol upgrades and market needs without breaking interoperability.

In short, Phase 1 isn’t just preparation — it’s a deliberate move to make Cardano more connected, more relevant, and more competitive in the global blockchain landscape. The outcomes of this phase will guide the technical execution in later stages, ensuring that every line of code, every integration, and every design choice amplifies Cardano’s value proposition to the wider crypto community.

[Your Project and Solution] Capabilities & Feasibility

What is your capability to deliver your project with high levels of trust and accountability? How do you intend to validate if your approach is feasible?

Capability & Accountability

• We have already developed a prototype, which can be experienced at https://br0x.vercel.app/
• The team has experience implementing Plutus (Cardano) and Solidity (EVM), and has successfully executed cross-chain projects. Progress will be managed through clear milestones, with code and testnet results made publicly available on GitHub. All smart contracts will undergo thorough logic and security checks before release.
• We manage the largest Cardano ADA Vietnam group on Facebook, fostering strong community engagement.
• Our team has successfully completed six funded proposals in Funds 7, 8, and 9 under the Vcoincheck project. Source: Lidonation

Feasibility Validation

A prototype (Figma + interactive web) will be built to test UX flows, followed by an end-to-end demo on testnet with Wanchain. Data will be verified using CBOR + BLAKE2b across both chains, and feedback will be collected from a test community.

Success Indicators

• UI/UX
• Users can complete the swap flow (mocked) without assistance.
• Timeline and explorer links always reflect the correct transaction state.
• Deposit verification appears instantly after quote request.
• Smart contract
• At least one successful Cardano → EVM and reverse swap on testnet.
• Refund executes successfully when timeout occurs.

[Milestones] Project Milestones

Milestone Title

Research & UI/UX Design (Month 1)

Milestone Outputs

• Comprehensive research document covering market needs, competitor analysis, and blockchain integration feasibility.
• Wireframes and interactive UI mockups for all major screens (swap flow, wallet connect, history, settings) in light/dark mode.
• User flow diagrams for key interactions (connect wallet, initiate swap, track swap status).
• Preliminary frontend architecture and API interaction plan.

Acceptance Criteria

• All primary workflows are visually mapped in Figma wireframes.
• Minimum of two design review cycles with stakeholder feedback implemented.
• Frontend architecture plan approved by technical lead.
• Documentation includes component list, state management strategy, and API data flow.

Evidence of Completion

• Figma prototype with clickable navigation across all planned screens.
• PDF export of UI/UX package including style guide and color themes.
• Research & architecture document stored in shared repository.
• Signed stakeholder approval in project log.

Delivery Month

1

Cost

15500

Progress

20 %

Milestone Title

Interactive Prototype Development (Months 2–3)

Milestone Outputs

• Clickable, interactive prototype with responsive layout and all UI components functional with mock data.
• Frontend framework set up (e.g., React + Tailwind) with routing, state management, and placeholder API hooks.
• Integrated wallet connection (testnet mode).
• Sample swap simulation with static data.

Acceptance Criteria

• All screens from Milestone 1 implemented in responsive, interactive format.
• Wallet connect and disconnect flows work in testnet.
• Component library implemented per style guide.
• Prototype passes internal QA checklist for usability and navigation.

Evidence of Completion

• Deployed prototype to staging server (Netlify/Vercel) with public link.
• Source code pushed to Git repository with documentation on setup.
• QA report signed off by product manager.
• Demo session recording stored in documentation folder.

Delivery Month

2

Cost

20000

Progress

40 %

Milestone Title

Core Swap Logic & Testnet Integration (Month 4)

Milestone Outputs

• Implementation of blockchain interaction layer with swap smart contract integration.
• Real testnet swap execution between two supported chains.
• Transaction history retrieval from blockchain explorer API.
• Error handling, swap status updates, and retry mechanisms.

Acceptance Criteria

• Swaps can be initiated and confirmed on testnet from connected wallet.
• Transaction details match blockchain explorer records.
• Swap status (pending, completed, failed) updates in real time.
• System passes functional QA on at least 20 simulated swaps.

Evidence of Completion

• Testnet deployment URL demonstrating live swaps.
• GitHub repo with code changes and commit history.
• QA log of test cases with pass/fail results.
• Recorded testnet swap session stored in documentation folder.

Delivery Month

1

Cost

20200

Progress

60 %

Milestone Title

Cross-Chain Bridge & Liquidity Routing (Months 5–6)

Milestone Outputs

• Cross-chain bridge integration for target EVM and Cardano-compatible networks.
• Liquidity routing module to find optimal path for swaps.
• Integration with proof relay system (e.g., Wanchain XFlows) for transaction verification.
• Admin tools for managing supported tokens and liquidity sources.

Acceptance Criteria

• Successful cross-chain swaps executed between at least two networks in testnet.
• Routing engine selects best liquidity path in under 3 seconds.
• Proof relay verification passes for all test transactions.
• Admin panel updates reflect instantly in swap UI.

Evidence of Completion

• Public testnet demo of cross-chain swap with routing visualisation.
• Bridge and routing code reviewed and merged into main branch.
• Verification logs from proof relay stored in repository.
• Admin tool walkthrough video recorded.

Delivery Month

2

Cost

20500

Progress

80 %

Milestone Title

Final Release & Documentation (Month 7–8)

Milestone Outputs

• Final UI polish, accessibility improvements, and bug fixes.
• Complete user onboarding flow with guide/tooltips.
• Public documentation site with API references and user manual.
• Release build deployed to production environment.

Acceptance Criteria

• All known high/medium priority bugs closed.
• User onboarding tested with at least 5 non-technical testers.
• Documentation site passes content review for completeness and clarity.
• Production deployment verified and operational.

Evidence of Completion

• Production URL with full functionality live.
• GitHub release tag & changelog for v1.0.
• PDF export of full documentation.
• Final project sign-off form signed by stakeholders.

Delivery Month

2

Cost

7200

Progress

100 %

[Final Pitch] Budget & Costs

Please provide a cost breakdown of the proposed work and resources

M1 – Research & UI/UX Design

1. Scope Summary: Finalize requirements, system architecture, UI concept, technical stack, and development plan. Deep dive into Cardano lock script, EVM lock contract, Wanchain XFlows PoC, backend architecture design.
2. Estimated Hours: ~220 hrs
3. Roles & Cost:

• PM: 2,500 ADA
• Solution Architect: 3,500 ADA
• UI/UX Designer: 3,000 ADA
• Blockchain Dev (PoC): 6,500 ADA

Total ADA: 15,500 ADA

M2 – Interactive Prototype Development

1. Scope Summary: Build interactive front-end prototype with sample data, navigation flows, swap UI mockups.
2. Estimated Hours: ~320 hrs
3. Roles & Cost:

• Frontend Dev: 12,000 ADA
• UI/UX Designer: 3,500 ADA
• QA Tester: 1,500 ADA
• PM: 2,000 ADA
• Tooling & Hosting: 1,000 ADA

Total ADA: 20,000 ADA

M3 – Core Swap Logic & Testnet Integration

1. Scope Summary: Implement functional interface components, wallet connect, swap form, history view, testnet mock API integration.
2. Estimated Hours: ~350 hrs
3. Roles & Cost:

• Frontend Dev: 12,000 ADA
• Backend/Integration Dev: 3,000 ADA
• UI/UX Support: 1,200 ADA
• QA: 2,000 ADA
• PM: 2,000 ADA

Total ADA: 20,200 ADA

M4 – Cross-Chain Bridge & Liquidity Routing

1. Scope Summary: Integrate swap smart contract on testnet, connect to lock scripts, handle tx signing, and run functional testing.
2. Estimated Hours: ~360 hrs
3. Roles & Cost:

• Blockchain Dev: 9,000 ADA
• Frontend Dev: 5,000 ADA
• Backend Support: 2,500 ADA
• QA: 2,000 ADA
• PM: 2,000 ADA

Total ADA: 20,500 ADA

M5 – Final Release & Documentation

1. Scope Summary: UI refinements, bug fixes, deployment pipeline, technical documentation, onboarding guide.
2. Estimated Hours: ~200 hrs
3. Roles & Cost:

• Frontend Dev: 3,500 ADA
• UI/UX: 1,200 ADA
• Content Writer: 1,500 ADA
• QA: 1,000 ADA
• PM: 1,500 ADA

Total ADA: 7,200 ADA

[Final Pitch] Value for Money

How does the cost of the project represent value for the Cardano ecosystem?

This proposal represents an exceptional return on investment for the Cardano ecosystem. By strategically structuring the work, we have eliminated unnecessary expenses while maintaining the highest level of technical and design quality. The team composition is intentionally compact — experienced professionals who can deliver at speed without bloated management layers. Leveraging remote collaboration, open-source tooling, and reusable design frameworks, we achieve a cost efficiency rarely seen in blockchain development.

Every ADA invested here builds lasting value: modular UI/UX assets that other projects can adopt, technical integrations that strengthen Cardano’s presence in cross-chain environments, and architectural designs that can be adapted for future governance or business applications. This means the outputs extend far beyond the life of the project, creating a multiplier effect in the ecosystem.

Economically, this proposal plants seeds for long-term growth. By lowering the barrier for businesses and developers to build on Cardano, it stimulates new dApp launches, transaction volume, and demand for ADA. The combination of lean execution, high reusability, and ecosystem-wide benefits ensures that every ADA spent works harder — generating both immediate deliverables and sustained economic impact for Cardano in the years ahead.

[Self-Assessment] Self-Assessment Checklist

I confirm that evidence of prior research, whitepaper, design, or proof-of-concept is provided.

Yes

I confirm that the proposal includes ecosystem research and uses the findings to either (a) justify its uniqueness over existing solutions or (b) demonstrate the value of its novel approach.

Yes

I confirm that the proposal demonstrates technical capability via verifiable in-house talent or a confirmed development partner (GitHub, LinkedIn, portfolio, etc.)

Yes

I confirm that the proposer and all team members are in good standing with prior Catalyst projects.

Yes

I confirm that the proposal clearly defines the problem and the value of the on-chain utility.

Yes

I confirm that the primary goal of the proposal is a working prototype deployed on at least a Cardano testnet.

Yes

I confirm that the proposal outlines a credible and clear technical plan and architecture.

Yes

I confirm that the budget and timeline (≤ 12 months) are realistic for the proposed work.

Yes

I confirm that the proposal includes a community engagement and feedback plan to amplify prototype adoption with the Cardano ecosystem.

Yes

I confirm that the budget is for future development only; excludes retroactive funding, incentives, giveaways, re-granting, or sub-treasuries.

Yes

[Required Acknowledgements] Consent & Confirmation

I Agree

Yes