zkbk

zkbk is a collection of zero-knowledge gadgets and verifiable credential primitives built on top of the arkworks ecosystem to facilitate first-person credentials.

The repository is structured as a Cargo workspace containing two main crates:

1. fp-snark: Packages reusable SNARK-friendly primitives—Merkle trees, vector commitments, polynomial utilities, pseudorandom functions, random oracles, and Schnorr signatures—together with circuit-friendly constraint gadgets and end-to-end Groth16 integration tests.
2. fp-blackbox: Implements black-box (pairing-based) cryptographic constructions. It currently includes:
   • gro15: Standard and Flipped Groth15 signatures.
   • gs08: Groth-Sahai proofs for pairing-based statements (e.g., SXDH commitment schemes, PPE proofs).
   • vouch: The Vouchable Credentials construction (issuance and vouching).

Getting Started

1. Install Rust (recommended via rustup) and ensure the stable toolchain is active.

2. Fetch dependencies and compile the workspace:

   cargo build

3. Generate docs if desired:

   cargo doc --open

Repository Layout

fp-snark

• fp-snark/src/lib.rs – Crate entry point.
• fp-snark/src/merkle_tree/ – Layered hash configuration trait, path verification, and fixed-height Merkle tree implementation.
• fp-snark/src/vector_commitment/bytes/ – Vector commitment interface for byte-array elements.
• fp-snark/src/record_commitment/ – Commitment schemes (Pedersen, KZG, SHA-256) with circuit gadgets for record construction.
• fp-snark/src/prf/ – JZ PRF abstraction backed by configurable CRHs plus constraint system gadgets.
• fp-snark/src/random_oracle/ – Random oracle trait and a Blake2s-backed implementation for both native and R1CS contexts.
• fp-snark/src/signature/ – Signature trait with a Schnorr implementation over JubJub.
• fp-snark/tests/ – Heavyweight integration tests that compose the primitives into Groth16 circuits (e.g., nullifier PRFs, Pedersen commitments, and membership checks). Design diagrams supporting several tests live under tests/designs/.

fp-blackbox

• fp-blackbox/src/lib.rs – Crate entry point.
• fp-blackbox/src/gro15/ – Implementation of standard and flipped Groth15 signatures.
• fp-blackbox/src/gs08/ – Implementation of Groth-Sahai proofs.
• fp-blackbox/src/vouch/ – Elements of the Vouchable Credentials construction.
• fp-blackbox/benches/ – Benchmarks for the fp-blackbox components.

Running Tests

The project includes both unit tests and integration tests. On most machines, you will want to enable optimizations:

cargo test --release

Contributing & License

Contributions are welcome; please open an issue or pull request with ideas or fixes. The project is licensed under the Apache License, Version 2.0. See LICENSE for details.