ZK Credential

This is my submission for ZK Hack Istanbul hackathon. The project is a proof of concept.

ZK Credential is a project that explores the use of Verifiable Credentials in maintaining privacy leveraging Zero-Knowledge Proofs (ZKP) in real-world scenarios.

Quick Start

The host program reads mock data from data.json file and passes the data to the guests.

1. First, make sure rustup is installed. The [rust-toolchain.toml][rust-toolchain] file will be used by cargo to automatically install the correct version.

2. Install Risc Zero Toolchain

To build all methods and execute the method within the zkVM, run the following command:

To run in development mode, run the following command:

RISC0_DEV_MODE=true cargo run

Caution - When running in DEV mode, the receipt is fake!

To run for production, and get a real receipt, run the following command:

cargo run

Overview

ZK Credential explores the utilization of Verifiable Credentials from eIDAS 2.0 for EU citizens, showcasing how these credentials can be used to hide sensitive information like maximum bid amounts in real estate bidding and social security numbers in other use cases.

Implementation

I have created two programs(guests):

1. Make a bid to a broker. Check if the bid is less than the maximum amount allowed by the bank.
2. Generalize the program to accept any Verifiable Credential - This is a proof of concept to show how the program can be generalized to accept any Verifiable Credential and validate against a given Predicate:
   • GT - Greater than
   • LT - Less than
   • EQ - Equal to
   • More to come...

1. Make a bid to a broker

The application employs two key Verifiable Credentials:

1. PersonCredential: A credential verified by a trusted electronic ID (eID) provider, affirming the identity of the individual.
2. HouseLoanCredential: A credential from a bank, detailing the maximum bid amount and the expiration date for the granted privilege. These credentials are signed by respective issuers and authenticated by the user.

Core Process:

1. Credential Submission: Bid size, PersonCredential and HouseLoanCredential.
2. The RISC Zero zkVM runs the guest code, which performs the following checks:
   • Validation of JWT signatures and data.
   • Comparison of the bid size with the loan amount. If the bid exceeds the loan amount, the process fails.
3. Output Generation: Upon successful validation, the system generates:
   • A Receipt with a cryptographic seal.
   • A Journal containing the public output, accessible via receipt.journal.

2. Generalize the program to accept any Verifiable Credential

Core Process:

1. Use of any Verifiable Credential: E.g. PersonCredential and a Predicate like GT, LT, EQ. and the name of the field to compare.

   let predicate = Predicate{
        field: String::from_str("date_of_birth").unwrap(),
        condition: GT,
        value: 19791001
    };

Technology Stack

RISC Zero zkVM Verifiable Credentials

Running proofs remotely on Bonsai

Note: The Bonsai proving service is still in early Alpha; an API key is required for access. [Click here to request access][bonsai access].

If you have access to the URL and API key to Bonsai you can run your proofs remotely. To prove in Bonsai mode, invoke cargo run with two additional environment variables:

BONSAI_API_KEY="YOUR_API_KEY" BONSAI_API_URL="BONSAI_URL" cargo run

Directory Structure

It is possible to organize the files for these components in various ways. However, in this starter template we use a standard directory structure for zkVM applications, which we think is a good starting point for your applications.

zkc
├── data.json                             <-- [Mock data - Verfiable Credentials, public keys, etc.]
├── Cargo.toml
├── host
│   ├── Cargo.toml
│   └── src
│       └── main.rs                        <-- [Host code for running the zkVM]
└── methods
    ├── Cargo.toml
    ├── build.rs
    ├── guests
    │   ├── bid_verifier
    │       ├── Cargo.toml
    │       └── src
    │           └── main.rs                   <-- [Guest code for house bid, jwt validation, etc.]
    │   └── predicate_verifier
    │       ├── Cargo.toml
    │       └── src
    │           └── main.rs                   <-- [Guest code for predicate validation, jwt validation, etc.]
    └── src
        └── lib.rs