generic_mpc

Experimental Axum relay for a t-of-n MPC wallet lifecycle:

• wallet creation and authenticated participant requests;
• GOLDEN-style DKG over the bjj-bn254-bp suite;
• local participant share reconstruction;
• FROST-style threshold signing where devices keep DKG secret shares local and the relay combines only per-session signature shares.

This repository is a pre-production PoC for protocol review and conformance work. Do not use it for internet-facing or high-value wallets.

Current Shape

The relay stores the public DKG/signing transcript and enforces phase, deadline, authorization, canonical CBOR, and replay rules. Participant devices own their local DKG secret shares. During signing, each selected device posts Round 1 commitments, then a Round 2 signature share for one message. The relay combines those signature shares into a self-contained signature envelope.

The linked suite is bjj-bn254-bp: Baby Jubjub for identity/NIKE inputs and BN254 G1 for output/VSS/Bulletproof commitments.

Useful Commands

cargo fmt --check
cargo clippy --all-targets -- -D warnings
cargo test --all-targets
GENERIC_MPC_RELAY_PORT=3903 scripts/live-smoke-2of3.sh

Run the relay:

GENERIC_MPC_RELAY_ADDR=127.0.0.1:3903 cargo run --release --bin relay

Drive a local 2-of-3 DKG plus signing smoke:

GENERIC_MPC_RELAY_PORT=3903 \
GENERIC_MPC_THRESHOLD=2 \
GENERIC_MPC_TOTAL=3 \
GENERIC_MPC_READY_SNAPSHOT_OUT=target/tmp/ready-wallet.cbor \
cargo run --release --bin drive_wallet

Replay signing from participant-local READY snapshots:

GENERIC_MPC_READY_SNAPSHOT_IN=target/tmp/ready-wallet.node-1.cbor,target/tmp/ready-wallet.node-2.cbor \
cargo run --release --bin sign_ready_snapshot

Code Map

• src/api.rs: Axum routes, auth, lifecycle state, relay-side signing combiner.
• src/dkg.rs: DKG session state machine.
• src/golden.rs: suite-facing GOLDEN algebra/provider boundaries.
• src/api/suite_bjj_bn254_bp.rs: registered bjj-bn254-bp provider.
• src/bjj_bn254_bp.rs: Round0 construction and verification helpers.
• src/bn254_bp.rs: Bulletproof-style R1CS/eVRF proof substrate.
• src/frost_bn254.rs: minimal BN254 FROST-style signing implementation.
• src/ready_snapshot.rs: participant-local READY fixture format.
• tests/ready_snapshot_replay.rs: fixture-backed threshold signing replay.

Local Docs

• tests/fixtures/README.md: participant-local READY fixture details.

References

• GOLDEN DKG: Bünz, Choi, Komlo, IACR ePrint 2025/1924, https://eprint.iacr.org/2025/1924
• FROST: RFC 9591, https://datatracker.ietf.org/doc/html/rfc9591
• Bulletproofs: Bünz et al., IACR ePrint 2017/1066, https://eprint.iacr.org/2017/1066
• HTTP Message Signatures: RFC 9421, https://www.rfc-editor.org/rfc/rfc9421.html
• Deterministic CBOR: RFC 8949, https://www.rfc-editor.org/rfc/rfc8949.html
• Baby Jubjub notes: https://iden3-docs.readthedocs.io/en/latest/iden3_repos/research/publications/zkproof-standards-workshop-2/baby-jubjub/baby-jubjub.html