A privacy-aware three-party escrow dApp with shielded tokens

[Proposal setup] Proposal title

Please provide your proposal title

A privacy-aware three-party escrow dApp with shielded tokens

[Proposal Summary] Time

Please specify how many months you expect your project to last

3

[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?

It can be difficult for new devs to understand how to properly mint and transfer shielded tokens to/from contracts, as well as how to make good use of the witnesses and private state.

[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 here more information on the open source status of your project outputs

MIT License

[Theme Selection] Theme

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

Education

[Campaign Category] Category Questions

What is useful about your DApp within one of the specified industry or enterprise verticals?

Developers which are new to Midnight will find it hard to understand how to use all the concepts this application demonstrate by putting them all together in a single real world use case.

It will help developers to learn how to seamlessly integrates these advanced cryptographic techniques to address real-world challenges, providing a robust framework for privacy-centered solutions in various sectors, such as finance, identity verification, and secure communications.

What exactly will you build? List the Compact contract(s) and key functions/proofs, the demo UI flow, Lace (Midnight) wallet integration, and your basic test plan.

The following flow is the main use case this dApp will be showcasing:

1. Seller publishes an offer to the marketplace.
2. Carriers place bids on the offer.
3. Buyer purchases the item and selects a carrier from the bidder list (delivery fee of each bidder is shown), and enters the delivery address which is encrypted to the selected carrier's Public key (asymmetric encryption used here).
4. Selected Carrier accepts the job and stakes a security deposit (equal to the deposit made by the buyer).
5. Carrier arrives to deliver, and marks the order as delivered onchain.
6. The buyer confirms it received the item: funds are released to seller and carrier.

In addition to that flow, users can mint shielded tokens which are neeed for the application.

How will other developers learn from and reuse your repo? Describe repo structure, README contents, docs/tutorials, test instructions, and extension points. Which developer personas benefit, and how will you gauge impact (forks, stars, issues, remixes)?

Developers will be able to clone or cherry-pick the codebase from the different components to be delivered by this app:

• A web UI written in React + TypeScript, demo-ready front-end (components, modals, and the main app).
• Contract source code
• Contract automated tests
• ZK witnesses code implementation and example private state implementation to manage asymmetric encryption in smart contracts.
• Backend integration with the contract, APIs and utility wrappers for calling contracts and proof-server endpoints.
• Easy to use web-based UI to excercise and demonstrate the features exposed by the smart contract and witnesses.

[Your Project and Solution] Solution

Please describe your proposed solution and how it addresses the problem

A reference dApp and a set of Compact circuits which showcases:

• The use of witnesses and private state, for safeguarding users data with asymmetric encryption and shielded identities.
• How shielded tokens can be minted by a contract, and transferred to users.
• How a real world marketplace could be decentralised by the implementation of a 3-party escrow system using a Compact smart contract.
• A simple web UI which interacts with the contract and integrates with Lace wallet.
• A comprehensive set of tests to verify the contract's circuits mutate the ledger state as expected.

[Your Project and Solution] Impact

Please define the positive impact your project will have on Midnight ecosystem

Reduce the amount of time developers, specially those who are new to the Midnight technology and development stack, or smart contract development, need to invest in order to understand, implement and deploy a dApp on Midnight for a real world use case, removing the expected and usual frustrations this implies for them at the very begining.

Being able to see how all these features are put together to create a real world application, such as a 3-party escrow decentralised marketplace with shielded tokens, should help developers to onboard onto Midnight development.

[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?

I have been a Software Engineer for 20+ years working on different technologies and programming languages (you can check my linkedin profile). A few months ago I started with smart contract development, I've been participating in a couple of hackathons delivering a couple of fully functional dApps which led me to understand the concepts and implementation details for the reference application I'm proposing to create:

• https://github.com/bochaco/dmarket
• https://github.com/bochaco/ataulfo

[Final Pitch] Budget & Costs

Please provide a cost breakdown of the proposed work and resources

Contract Source Code

Description: Smart contract code that will form the core logic of the application.

Estimated Cost: $USDM 2000

Functionality: Implementing all features described, i.e. shielded tokens minting, 3-party escrow system, marketplace functionality, shielded identities, asymmetric encryption through witnesses.

Contract Automated Tests

Description: Automated testing scripts for the smart contract to ensure functionality and reliability.

Estimated Cost: $USDM 1500

Test Coverage: Writing comprehensive tests for all contract circuits.

Continuous Integration Setup: Setting up CI/CD pipelines for automated testing.

ZK Witnesses Code Implementation

Description: Implementation of ZK witnesses and example private state management to facilitate asymmetric encryption.

Estimated Cost: $USDM 1300

Witnesses Logic: Development of the witnesses logic for zk-proofs.

Backend Integration and CLI

Description: Integration of the backend with the contract, including APIs and utility wrappers for calling contracts and proof-server endpoints.

Estimated Cost: $USDM 1500

API Development: Building APIs for frontend interaction.

Utility Wrappers: Simplifying contract calls for easier usage.

CLI: basic CLI to showcase the main use cases.

Web-Based UI for Feature Demonstration

Description: A user-friendly web interface to demonstrate the features exposed by the smart contract and witnesses, built using React and TypeScript, including components, modals, and the main app.

Estimated Cost: $USDM 2000

Components: Development of reusable UI components.

Usability Design: Ensuring the UI is intuitive and easy to navigate.

Integration & Responsiveness: Ensuring the UI is responsive and integrates well with backend services.

[Final Pitch] Value for Money

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

By significantly reducing the time developers need to comprehend, implement, and deploy a dApp with the showcased features, we will encourage sustained investment in the Midnight platform. This streamlined approach not only enhances individual engagement but also empowers developers to invite colleagues, coworkers, and friends to explore Midnight. Consequently, this collaborative effort can ignite the development of next-generation applications on this innovative network, while also fostering community growth and involvement.

[Self-Assessment] Self-Assessment Checklist

I confirm that the proposal clearly provides a basic prototype reference application for one of the areas of interest.

Yes

I confirm that the proposal clearly defines which part of the developer journey it improves and how it makes building on Midnight easier and more productive.

Yes

I confirm that the proposal explicitly states the chosen permissive open-source license (e.g., MIT, Apache 2.0) and commits to a public code repository.

Yes

I confirm that the team provides evidence of their technical ability and experience in creating developer tools or high-quality technical content (e.g., GitHub, portfolio).

Yes

I confirm that a plan for creating and maintaining clear, comprehensive documentation is a core part of the proposal's scope.

Yes

I confirm that the budget and timeline (3 months) are realistic for delivering the proposed tool or resource.

Yes

[Required Acknowledgements] Consent & Confirmation

I Agree

Yes