Eryx - zkCredentials: Unlocking Privacy-First Applications

[Proposal setup] Proposal title

Please provide your proposal title

Eryx - zkCredentials: Unlocking Privacy-First Applications

[Proposal Summary] Budget Information

Enter the amount of funding you are requesting in ADA

164900

[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?

Cardano lacks practical on-chain identity solutions that offer easy-to-adopt selective disclosure, and a clear path to private verification. This makes many applications unappealing on-chain.

[Proposal Summary] Supporting Documentation

Supporting links

• https://crypto.eryx.co/

[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.

The implementation will be open source and available on GitHub under the Apache 2.0 license.

[Theme Selection] Theme

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

Identity & Verification

[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).

Cardano's current digital identity is binary: either you share everything (name, ID, birthdate, address) or nothing at all. We’re bringing selective disclosure to Cardano. You prove only what’s needed, keep the rest private.

We will use the power of zero-knowledge proofs to address this limitation. Our system allows users to prove facts like "age over 18" or "citizenship in approved list" without exposing the underlying data (birthdate, passport number, etc.). This attribute-level privacy can be achieved using cryptographic primitives such as Merkle trees and ZK proofs.

Furthermore, in the model we propose, a credential issuer publishes their signatures on Cardano and then anyone can verify credentials independently. There is no need to check back with the issuer. This enables permissionless innovation since developers can build verification into their dApps.

Potential usecases include:

• Nationality-based promotions (like Devconnect 2025 did with Argentine citizens using QuarkID)
• Employee benefits (prove employment without revealing salary or personal details)
• Reusable KYC credentials across DeFi protocols
• Government services (prove citizenship/residency)
• NFT credentials for degrees or event tickets

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

The prototype will demonstrate a complete zero-knowledge credential lifecycle on Cardano testnet. Deliverables include the full architecture of the solution, the contract for the credential issuer, the functional ZK circuits so that the user can build proofs on their credentials, and the verifier contract that can be run on-chain. A reference application will show the complete user journey: receiving a credential from an issuer, generating a zero-knowledge proof about credential properties (without revealing the underlying attributes), and having that proof verified both on-chain or off-chain via signature validation. The codebase will be available on GitHub under open-source licensing and will be accompanied by comprehensive documentation, code examples, and integration guides enabling other Cardano projects to incorporate privacy-preserving credentials.

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

If successful, we envision:

• A complete example that tests the whole framework deployed on testnet, as described above.
• Codebase publicly available in Github with an open source license.
• Documentation and tutorials publicly available.

[Your Project and Solution] Solution

Please describe your proposed solution and how it addresses the problem

We propose building a zero-knowledge credential system on Cardano that enables selective disclosure of identity attributes. The system allows credential issuers, such as universities, employers, KYC providers, government agencies, to create digital credentials containing user attributes (age, citizenship, employment status, educational qualifications) organized in a Merkle tree (or similar) structure.

Issuers make a transaction describing a specific credential that they will emit. This transaction describes the attributes it will have (For instance a government ID would have attributes such as name, date of birth, place of birth, etc) along with the public keys they will use to sign the credentials.

When a user wants to get a credential, they validate their identity with the issuer and get a signed commitment to those attributes. Users receive their complete credentials off-chain and can generate zero-knowledge proofs demonstrating specific properties about their attributes without revealing the underlying data.

zkCredentials Proposed Flow: https://i.ibb.co/Y4bGGJr1/zk-Credential-Flow.jpg

The system addresses Cardano's current identity limitation by adding a capability that, to our current knowledge, doesn't exist in production today.

Our solution leverages cryptographic proofs that are mathematically sound (users cannot forge claims about credentials they don't possess) while revealing only the minimum necessary information. Verifiers can check these proofs either on-chain through smart contracts or off-chain using the issuer's published public keys, enabling both high-security applications (DeFi KYC, legal credentials) and high-frequency use cases (login authentication, routine eligibility checks).

The system is designed as open infrastructure: all code is open-source, and will enable any Cardano developer to integrate privacy-preserving verification without cryptographic expertise.

[Your Project and Solution] Impact

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

Privacy is now a trending topic in the whole Web3 ecosystem. Working on this project, among others, tackles Cardano's current lack of privacy-preserving real-world applications. Adopting these technologies may attract the big community of privacy-first users from Cardano and other blockchains.

This project enables several high-value use cases, each generating sustained transaction volume and attracting new user segments.

• Corporate employee credential systems allow companies to issue verifiable employment credentials that employees can use to access discounts and benefits across multiple vendors without revealing salary information, department details, or other sensitive employment data. Vendors simply verify "this person is employed by Company X" on-chain.
• KYC credential providers can issue compliance credentials that users could present to any DeFi protocol or regulated service in the Cardano ecosystem, eliminating redundant identity verification across platforms while maintaining privacy; users prove "I completed KYC with an approved provider" and "I am not from a restricted jurisdiction" without doxxing their identity.
• Government agencies can issue citizenship or residency credentials enabling citizens to access public services, vote in governance systems, or prove eligibility for benefits while minimizing personal data collection by individual departments.
• Education institutions could issue diploma NFTs linked to credentials.
• Event organizers would be able to issue ticket NFTs where holders prove legitimate purchase without exposing transaction history or personal information.
• DAOs can verify voter eligibility based on token holdings or reputation without correlating votes to identities
• Marketplaces can implement age restrictions.

Each credential issuance, proof generation, and verification creates on-chain transactions, translating to measurable, utility-driven activity beyond speculative trading. Also, by providing open-source infrastructure, we lower the barrier for any project to add privacy features. This positions Cardano competitively against ecosystems that already offer zero-knowledge credentials, attracts privacy-conscious developers and institutions whose current Cardano's identity solutions don't exactly meet their needs.

[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?

Eryx is a worker-owned labor cooperative with almost 15 years of experience solving complex problems involving mathematics and software. We are a group of nerdy PhDs with a solid background in math and computer science. Our team has extensive experience in blockchain development, cryptography, and privacy-focused protocols, which gives us the expertise required to successfully deliver the project.

We have already implemented proving systems and other ZK protocols. We’ve been core contributors to the Lambdaworks library, which implements several proving systems, including PLONK. We also implemented the CircleSTARKS protocol in GPU alongside with Nethermind. Both these projects involved implementing several ZK cryptographic primitives such as field operations, elliptic curve operations, Merkle trees, polynomial commitment schemes, FRI protocols, FFTs among others, in different platforms and languages. We also wrote a simple interface to design circuits. It included basic operations and conditionals that made the building blocks for more complex cryptographic primitives.

There is no doubt that the team is capable of completing this proposal.

Feasibility comes from the fact that the project uses cryptographic primitives that are already working in Cardano such as digital signatures, Merkle trees, and ZK proofs.

[Milestones] Project Milestones

Milestone Title

Protocol architecture and documentation

Milestone Outputs

• Technical review of the research done:
  • Design and architecture of the solution.
  • Contract design for credential issuing and verification.
  • Circuit design for selective disclosure.
  • Merkle tree or similar hash based credential structure documentation.

Acceptance Criteria

The documentation covers the full protocol, this will include:

• Initial setup where an entity will publish a set of public keys that will be used to generate credentials and the credential data scheme
• Credentials issuing. The documentation will also cover the implementation of the credentials.
• Proof generation of credentials data.
• Verification of the generated proofs. We will explore on-chain and off-chain alternatives.

Evidence of Completion

A public Github repository with the all documentation and research, under the appropriate open source license.

Delivery Month

1

Cost

57715

Progress

30 %

Milestone Title

Initial setup and credential generation

Milestone Outputs

• Write Aiken code that validates the transaction needed for an entity initial setup. This transaction must have:
  • The credentials scheme
  • A set of public keys used to sign credentials
• Write JS code that receives user information as input and generates a signed credential for this data. The information used to build the credential will be defined in milestone 1. This code will be meant to run in a frontend application.

Acceptance Criteria

An entity is able to:

• use this code to publish the credentials scheme and the public keys that will be used to sign the credentials.
• generate a signed credential with users information when requested.

Evidence of Completion

The Github repository will contain this code and usage documentation will be provided, under the appropriate open source license.

Delivery Month

2

Cost

57715

Progress

70 %

Milestone Title

Generate and verify a proof of some data from a credential

Milestone Outputs

• Code that generates a proof of some property of the data used to issue the credential (e.g., a user is over 18). This code must keep all credential information private except for the property being proven. We could generate the proofs using Circom, but we may switch if, during our research, we find another language more suitable for using this tool on Cardano.
• Aiken code to verify the generated proof on-chain.

Acceptance Criteria

• A user can demonstrate that their credential satisfies a certain attribute without revealing any additional information.
• A third party can verify that the proof is valid based on the credential and the public key that was used to sign that credential.

Evidence of Completion

The Github repository will contain this code and usage documentation will be provided, under the appropriate open source license.

Delivery Month

3

Cost

32980

Progress

90 %

Milestone Title

Close-out report

Milestone Outputs

• A final report describing the project process and outcome.
• A video showcasing the tool and its features.
• Full documentation for developers, including setup, usage, and contribution guidelines.
• User-friendly setup and usage tutorials.

Acceptance Criteria

• The tool meets all functional expectations. Documentation and tutorials are complete and clear.
• The final video complies with Catalyst requirements
• The final report complies with Catalyst requirements

Evidence of Completion

• Source-code available in the GitHub repository
• Documentation publicly available
• Final video uploaded to Google drive or similar platform
• Final report uploaded to Google drive or similar platform

Delivery Month

3

Cost

16490

Progress

100 %

[Final Pitch] Budget & Costs

Please provide a cost breakdown of the proposed work and resources

Total: ₳164,900

FTE = Full-time equivalent

• Development: ₳150,000 total.
  • The activities of this item will be: Smart Contract Development; Implementation of math primitives and cryptographic protocols, writing technical documentation.
    • Cardano developer: FTE x 3 months = ₳50,000
    • Cardano developer: FTE x 3 months = ₳50,000
    • Zero-Knowledge Cryptographer: FTE x 3 months = ₳50,000
• Project management: ₳14,900
  • The activities of this item will be: Organize the project execution, create reports and write the documentation, and maintain communication with the community and reviewers.
    • Project Management: ½ FTE x 3 months = ₳14,900

[Final Pitch] Value for Money

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

We decided to focus on spending the expenses of the project in the development hours. In that regard, it is important to note the following.

The team consists of three developers who will work full-time on the project for three months. The projected annual salary is within the typical salary range for developers, which varies from $78,000 to $262,000, with an average of $150,000 for a Web3 developer. Our cost is on the lower end of this range.

[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