MidnightZK Off-Ramp SDK: ADA↔Web2 Payments (Cash App, Wise)

[Proposal setup] Proposal title

Please provide your proposal title

MidnightZK Off-Ramp SDK: ADA↔Web2 Payments (Cash App, Wise)

[Proposal Summary] Budget Information

Enter the amount of funding you are requesting in ADA

80000

[Proposal Summary] Time

Please specify how many months you expect your project to last

4

[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?

ADA & CNT holders lack an open-source, non-custodial solution to privately off-ramp to make real-world payments via Cash App, Wise, or Revolut, forcing reliance on costly, custodial services.

[Proposal Summary] Supporting Documentation

Supporting links

• https://app.nucast.io/
,
• https://www.nucastlabs.xyz/
,
• https://x.com/NucastIO

[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

License and Additional Information

MIT License

[Theme Selection] Theme

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

Developer Tools

[Campaign Category] Category Questions

Mention your open source license and describe your open source license rationale.

We will release the project under the MIT License, a widely adopted, permissive open-source license.

Rationale:

Encourages broad adoption and integration across Web3 and Web2 ecosystems without restrictive terms.

Allows both individuals and enterprises to modify, distribute, and use the code in proprietary or open-source projects.

Maximises developer contributions by removing licensing barriers, ensuring faster iteration and innovation.

Compatible with Cardano ecosystem principles of openness, transparency, and interoperability.

How do you make sure your source code is accessible to the public from project start, and people are informed?

Repository will be public from project start on GitHub, with clear README and contribution guidelines.

All development tracked via version control with meaningful commit messages and tagged releases.

Regular progress updates shared through GitHub issues, pull requests, and Cardano community channels.

Key milestones, releases, and feature additions will be publicly announced on X/Twitter to ensure transparency.

How will you provide high quality documentation?

Comprehensive README, setup guides, and API documentation for both end-users and developers.

Clear structure with examples, code snippets, and visuals for ease of integration.

Documentation hosted using Gitbook for API references.

Step-by-step guides for installing, configuring, and extending the toolkit.

[Your Project and Solution] Solution

Please describe your proposed solution and how it addresses the problem

We propose developing an open-source, Midnight zero-knowledge-powered (ZK) non-custodial ADA off-ramp SDK that enables seamless, private, and low-cost transfers from ADA to fiat via Cash App, Wise, and Revolut without relying on centralized exchanges or custodial intermediaries.

The solution will be a developer-friendly SDK + API layer that dApps, wallets, and merchants can integrate directly into their platforms, providing end users with the ability to:

• Off-ramp ADA securely and privately into supported Web2 payment platforms.
• Preserve privacy using Midnight zero-knowledge proofs, ensuring only essential payment verification data is shared without revealing personal transaction history.
• Avoid KYC where legally possible, by leveraging peer-to-peer payment rails and hashed identifiers stored on-chain.
• Retain full control of funds, as all transactions are initiated from the user’s own wallet, never held in custody by the service.

Core Features:

MidnightZK-Powered Privacy Layer

• Uses MidnightZK proofs to validate transaction intent and payment details without exposing raw data.
• Off-chain storage of sensitive account details, with hashed on-chain references for transparency.

Multi-Platform Support

• Direct integration for Cash App, Wise, and Revolut payouts.
• Ability for developers to easily extend support for additional payment processors in the future like Venmo.

Non-Custodial Escrow & Settlement

• Smart contracts on Cardano handle temporary escrow for conversion before releasing fiat via integrated payment rails.
• No third-party holds user funds, escrow is fully automated and trustless.

Open-Source SDK

• Fully documented library for integration into dApps, wallets, merchant PoS systems, and remittance services.
• Code released under the MIT License, ensuring anyone can audit, fork, or improve the toolkit.

Developer & User Experience

• Redirect-based flow for simple integration with existing platforms.
• Option for embedded flows for advanced implementers, minimizing user friction.

How it addresses the problem:

This SDK removes the barriers of cost, complexity, and trust currently limiting ADA off-ramping to Web2 payment platforms. Instead of depending on centralized exchanges with long withdrawal delays, high fees, and invasive KYC, ADA users can send value directly to widely used fintech apps (Cash App, Wise, Revolut) in minutes securely and with their privacy preserved.

By making this open-source, the project ensures that the Cardano ecosystem benefits from a shared, verifiable, and extensible payment bridge that can be adopted globally, accelerating real-world ADA usage.

With 100M+ combined active users across Cash App (57M), Wise (16M), and Revolut (~40M), processing hundreds of billions in annual transaction volume, this solution unlocks ADA’s direct path into some of the most widely used fintech rails in the world. By enabling instant, private, and non-custodial off-ramps into these everyday payment platforms, we are turning ADA into spendable money anywhere, from buying coffee to paying rent, without the friction, fees, and gatekeeping of centralized exchanges. This is not just off-ramping, it is real-world ADA adoption at scale.

[Your Project and Solution] Impact

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

This project will deliver a transformative boost to ADA’s real-world utility by enabling open-source, non-custodial, privacy-preserving off-ramps to widely used Web2 payment platforms Cash App, Wise, and Revolut directly from the Cardano blockchain.

1. Expanding Real-World ADA Utility

Currently, off-ramping ADA into fiat via common fintech platforms requires centralized exchanges, KYC-heavy processes, and high fees, barriers that discourage everyday use. By providing a decentralized, developer-friendly toolkit, we empower wallets & dApps to integrate ADA-to-fiat payouts instantly, boosting Cardano’s presence in day-to-day financial activity.

2. Strengthening Cardano’s Position in the Global Payments Market

Cash App, Wise, and Revolut have a combined user base of over 150 million people worldwide. Direct integration with these platforms dramatically increases ADA’s accessibility, helping Cardano compete as a global payments infrastructure alongside traditional fintech and banking solutions.

3. Driving Open-Source Innovation

By releasing the SDK and smart contracts under the MIT License, we create a foundation for other developers to build upon whether for remittances, DeFi payouts, or gaming rewards.

4. Preserving Privacy While Maintaining Trust

Our use of zero-knowledge proofs (ZKPs) ensures that users can off-ramp funds without exposing personal financial histories, while still providing verifiable transaction proof to payment processors. This aligns with Cardano’s vision of privacy-enhanced, decentralized finance that operates within compliance boundaries.

5. Lowering Costs and Increasing Adoption in Underserved Markets

Many developing regions rely on fintech platforms like Wise for affordable cross-border payments. By reducing fees, removing centralized intermediaries, and enabling instant settlement, this project supports financial inclusion—empowering unbanked and underbanked communities to transact globally using ADA.

Key Measurable Impacts:

Trnsaction Volume: ADA-to-fiat transactions executed via the toolkit.

Cost Savings: Reduction in average off-ramp fees compared to centralized exchanges.

By bridging ADA with everyday financial platforms in a decentralized, private, and accessible way, this project strengthens Cardano’s role as a truly global, real-world financial network driving adoption far beyond the blockchain-native 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?

Our development team is highly skilled, with extensive experience in blockchain development, specifically on the Cardano platform. We have successfully contributed to several Cardano-based projects and are proficient in Cardano dApp development

Zero-Knowledge Proof Expertise: Our team includes Midnight ZK Pioneers with deep expertise in implementing Zero-Knowledge Proof (ZKP) techniques, which are essential to ensuring privacy and data protection within NuAuth.

We also won first prize at the Midnight Hackathon at Rare Evo -

https://x.com/nucastio/status/1824983712913633446?s=46&t=ViPsv-qfsWrzHwVx49F2tQ

Proven Track Record: Our team has a history of delivering complex blockchain solutions that are recognized for their innovation and impact. We have successfully deployed blockchain-based projects that required meticulous planning and robust technical execution. For more details on our previous work https://www.nucastlabs.xyz/

To ensure trust and accountability, we operate with open-source transparency. All code, smart contracts, and documentation will be released under the MIT License and made publicly available for community review. Development progress will be shared via GitHub, with detailed milestones and deliverables tracked in real time.

Feasibility will be validated through integration testing with selected wallet and partners to confirm reliability, security, and user experience.

Our deep involvement in the Cardano community through regular technical contributions, educational content, and ecosystem support demonstrates our commitment to delivering with integrity and to the highest standards of trust.

Budgeting and Financial Reporting: We will maintain a transparent budget and provide for the community according to the Catalyst guidelines. Regular updates on our progress, challenges, and milestones will be shared with the Cardano community via forums and social media. We will actively seek and incorporate community feedback.

[Milestones] Project Milestones

Milestone Title

Project Initiation & SRS (Software Requirements Specification)

Milestone Outputs

Detailed SRS document outlining functional and non-functional requirements.

Defined integration scope for Cash App, Wise, and Revolut off-ramps.

Identification of compliance considerations and ZKP privacy parameters.

Acceptance Criteria

Software Requirements Specification(SRS) document prepared by project leads.

Functional scope validated against user stories.

Risk assessment and mitigation strategies documented in the SRS document.

Evidence of Completion

Published SRS in the project's public GitHub repository in PDF format.

Project initiation document submitted.

Delivery Month

1

Cost

25000

Progress

20 %

Milestone Title

Technical Architecture Design

Milestone Outputs

High-level architecture diagram covering on-chain and off-chain components.

Data flow diagrams for ADA → USD conversion and ZK-verified off-ramp.

API integration design for Cash App, Wise, and Revolut.

Smart contract interaction models for escrow and ZKP payee verification.

Acceptance Criteria

Technical architecture document prepared by the development team.

Scalability, privacy and security considerations documented in the architecture.

Alignment with open-source standards and MIT licensing.

Evidence of Completion

Technical architecture document in GitHub repository.

Documented API specs and integration points.

Delivery Month

2

Cost

25000

Progress

40 %

Milestone Title

Development & Internal Testing

Milestone Outputs

Development of SDK and integration scripts for wallet/off-ramp apps.

Implementation of ZKP-based payee privacy mechanism.

Smart contract deployment to Cardano testnet for escrow logic.

Sandbox integration with Cash App, Wise, and Revolut test environments.

Acceptance Criteria

ZKP-based payee privacy mechanism correctly generates, verifies, and validates proofs without exposing sensitive data.

Smart contracts deploy successfully to the Cardano testnet and perform escrow logic as designed.

Sandbox integrations with Cash App, Wise, and Revolut APIs complete without errors, enabling simulated ADA-to-fiat transactions.

Evidence of Completion

Public testnet demo link.

GitHub code commits showing working SDK & contracts.

Internal testing report with transaction success rates and performance metrics.

Delivery Month

3

Cost

20000

Progress

90 %

Milestone Title

Final Testing, Documentation & Project Closure

Milestone Outputs

Comprehensive developer documentation for integration provided in gitbook.

Final project report summarizing achievements, lessons learned, and next steps.

SDK launch and marketing on social media - (twitter/x)

Acceptance Criteria

Comprehensive developer documentation published in GitBook, covering integration steps, API references, and example implementations.

Final project report completed, detailing achievements, challenges, lessons learned, and recommended next steps for ecosystem adoption.

Evidence of Completion

Public GitHub repository with final SDK & docs.

Final project closure report shared with Catalyst.

Recorded demo walkthrough video.

Delivery Month

4

Cost

10000

Progress

100 %

[Final Pitch] Budget & Costs

Please provide a cost breakdown of the proposed work and resources

Milestone 1 – Project Initiation & SRS – 25,000 ADA

Project Manager: 8,000 ADA

Senior Cardano Developer: 10,000 ADA

Operations & Research: 7,000 ADA

Milestone 2 – Technical Architecture Design – 25,000 ADA

Project Manager: 6,000 ADA

Senior Cardano Developer: 12,000 ADA

Junior Cardano Developer: 7,000 ADA

Milestone 3 – Development & Internal Testing – 20,000 ADA

Project Manager: 5,000 ADA

Senior Cardano Developer: 10,000 ADA

Junior Cardano Developer: 5,000 ADA

Milestone 4 – Final Testing, Documentation & Project Closure – 10,000 ADA

Project Manager: 5,000 ADA

Senior Cardano Developer: 5,000 ADA

Total Budget: 80,000 ADA

[Final Pitch] Value for Money

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

This project delivers a critical open-source ZK-powered, non-custodial ADA-to-Web2 payments integration for Cash App, Wise, and Revolut. By enabling direct, private, and trustless off-ramping without centralized custody, it removes one of the biggest barriers to real-world ADA adoption.

The budget is tightly aligned with essential development milestones, covering only core personnel and operational costs required for delivery.

The output will be fully open-source, allowing any Cardano project to integrate this payment capability without building it from scratch. This reduces duplication of effort across the ecosystem, accelerates adoption, and ensures long-term utility at no recurring cost to the community.

We follow a lean development approach, where we prioritize features and improvements based on real-time feedback from our partners, users, and the broader Cardano community. This method ensures that our resources are directed toward the most impactful areas, improving both development speed and cost-effectiveness.

Every ADA invested will result in a high-impact, reusable tool that empowers developers and users to transact seamlessly between Cardano and widely used Web2 payment platforms unlocking new economic activity and expanding Cardano’s global footprint.

[Required Acknowledgements] Consent & Confirmation

Terms and Conditions:

Yes