mpc/LLM.md

LLM.md - Hanzo MPC Signer Architecture & Development Guide

This document provides comprehensive guidance for AI assistants working with the Hanzo MPC (Multi-Party Computation) codebase.

📚 Overview

Hanzo MPC is a threshold signing service that provides:

• ECDSA (secp256k1) for Bitcoin/Ethereum/EVM chains
• EdDSA (Ed25519) for Solana/Polkadot/Sui
• Threshold signatures (t-of-n) with CGGMP21 protocol
• Key resharing for rotation without changing addresses

Architecture Position

Hanzo MPC is designed as a pluggable signer backend for Hanzo KMS:

┌─────────────────────────────────────────────────────────────────┐
│                      Hanzo KMS (Control Plane)                  │
│  ┌──────────┬─────────────┬──────────────┬─────────────────┐    │
│  │ Policy   │ Approvals   │  Audit Log   │  Key Registry   │    │
│  └────┬─────┴──────┬──────┴───────┬──────┴───────┬─────────┘    │
│       │            │              │              │              │
│  ┌────▼────────────▼──────────────▼──────────────▼─────────┐    │
│  │              Unified Signing API                         │    │
│  └────┬────────────┬──────────────┬──────────────┬─────────┘    │
│       │            │              │              │              │
│  ┌────▼────┐  ┌────▼────┐   ┌─────▼─────┐  ┌─────▼─────┐        │
│  │  HSM    │  │  MPC    │   │  Software │  │  Remote   │        │
│  │ Signer  │  │ Signer  │   │  Signer   │  │  Signer   │        │
│  └─────────┘  └─────────┘   └───────────┘  └───────────┘        │
└─────────────────────────────────────────────────────────────────┘

Product Architecture

1. Hanzo KMS Platform (Control Plane)

   • Key registry + metadata
   • Policy + workflow (quorum, time locks, spend limits, allowlists)
   • Audit log
   • Unified API
   • Secrets manager

2. Hanzo MPC Signer (This Project - Data Plane)

   • DKG / key share management
   • Threshold signing sessions
   • Reshare/rotate shares
   • Optional hardware-rooted modes

3. Hanzo HSM (Alternative Signer)

   • HSM-backed keys for classic KMS workloads
   • HSM-sealed share storage for MPC nodes

4. Hanzo Treasury (Optional UI)

   • Transaction building + chain adapters
   • Simulation / policy previews
   • Approvals UI (backed by KMS workflow engine)

🚀 Quick Start

Build and Install

# Build binaries
make build

# Or install directly
go install ./cmd/hanzo-mpc
go install ./cmd/hanzo-mpc-cli

Basic Usage

# Generate peers configuration
hanzo-mpc-cli generate-peers -n 3

# Register peers to Consul
hanzo-mpc-cli register-peers

# Generate event initiator
hanzo-mpc-cli generate-initiator

# Generate node identity
hanzo-mpc-cli generate-identity --node node0

# Start MPC node
hanzo-mpc start -n node0

📁 Project Structure

/Users/z/work/hanzo/mpc/
├── cmd/                    # Command-line applications
│   ├── hanzo-mpc/         # Main MPC node binary
│   └── hanzo-mpc-cli/     # CLI tools for configuration
├── pkg/                    # Core packages
│   ├── client/            # Go client library
│   ├── mpc/               # MPC implementation (TSS)
│   ├── kvstore/           # BadgerDB storage
│   ├── messaging/         # NATS messaging
│   ├── identity/          # Ed25519 identity management
│   └── eventconsumer/     # Event processing
├── e2e/                    # End-to-end tests
├── examples/               # Usage examples
└── scripts/                # Utility scripts

🏗️ Core Components

1. MPC Engine

Based on threshold cryptography:

• CGGMP21 protocol for ECDSA (secp256k1) - IMPLEMENTED & TESTED
• FROST protocol for EdDSA (Ed25519) - IMPLEMENTED & TESTED (keygen generates both ECDSA and EdDSA keys)
• Configurable threshold (t-of-n)
• Default: t = ⌊n/2⌋ + 1 (majority)

2. Storage Layer: BadgerDB

• AES-256 encrypted key shares
• Session data persistence
• Automatic backups

3. Messaging: NATS JetStream

• Pub/sub for broadcasts
• Direct messaging for P2P
• Message persistence

4. Service Discovery: Consul

• Node registration
• Health checking
• Configuration management

5. Identity: Ed25519 keypairs

• Node authentication
• Message signing/verification
• Encrypted with Age

🔧 Configuration

# config.yaml
environment: development
consul:
  address: localhost:8500
nats:
  url: nats://localhost:4222
badger_password: "secure-password"
event_initiator_pubkey: "hex-encoded-pubkey"

Environment Variables

• HANZO_MPC_CONFIG - Path to config.yaml
• HANZO_MPC_BACKUP - Backup file identifier

🔐 Security Model

• Threshold Security: No single node has the complete key
• Message Authentication: All messages signed with Ed25519
• Storage Encryption: BadgerDB encrypted with user password
• Network Security: TLS + mutual authentication
• Key Rotation: Supports resharing without changing addresses

📊 Performance

• Key Generation: ~30s for 3 nodes
• Signing: <1s for threshold signatures
• Storage: ~100MB per node (with backups)
• Network: Low bandwidth, resilient to failures

🔗 Integration with Hanzo Commerce

The MPC Signer integrates with Commerce for crypto payments:

// Commerce uses MPC via the processor interface
type MPCProcessor struct {
    kmsClient  *kms.Client   // Hanzo KMS for policy/approval
    mpcClient  *mpc.Client   // Hanzo MPC for signing
}

func (p *MPCProcessor) Charge(ctx context.Context, req PaymentRequest) (*PaymentResult, error) {
    // 1. KMS validates policy and approvals
    // 2. MPC signs the transaction
    // 3. Transaction broadcast to blockchain
}

🔧 Development Workflow

Testing

# Run unit tests
make test

# Run with coverage
make test-coverage

# Run E2E tests
make e2e-test

Common Tasks

1. Generate 3-node test cluster:

   ./setup_identities.sh
   

2. Recover from backup:

   hanzo-mpc-cli recover --backup-dir ./backups --recovery-path ./recovered-db
   

3. Production deployment:

   • Use --encrypt flag for identity generation
   • Enable TLS on all services
   • Use --prompt-credentials to avoid hardcoded passwords

🐛 Common Issues

1. Port conflicts: Default ports are 4222 (NATS), 8500 (Consul)
2. Database locks: Ensure single process per node
3. Network delays: Check NATS/Consul connectivity
4. Backup failures: Verify disk space and permissions

CGGMP21 Protocol Issues (Debugged Jan 2026)

5. Protocol message serialization: Protocol messages MUST use MarshalBinary/UnmarshalBinary to preserve all fields (SSID, RoundNumber, etc.). Raw JSON marshaling loses critical protocol state.

6. Party ID ordering: Party IDs must be sorted consistently across all nodes. The GetReadyPeersIncludeSelf() function in registry.go sorts peer IDs to ensure deterministic ordering.

7. NATS topic naming: Result topics must match JetStream stream configuration:

   • Keygen results: mpc.mpc_keygen_result.<walletID> (note the mpc.mpc_ prefix)
   • Signing results: mpc.mpc_signing_result.<walletID>
   • Stream expects pattern: mpc.mpc_*_result.*

8. Self-message rejection: It's NORMAL for nodes to log "Handler cannot accept message" warnings when they receive their own broadcast messages back. This is expected behavior in pub/sub systems.

9. Binary rebuild for e2e tests: E2E tests use hanzo-mpc from PATH. After code changes, run go install ./cmd/hanzo-mpc && go install ./cmd/hanzo-mpc-cli to update the installed binaries.

10. Session result publishing pattern: Individual protocol sessions (CGGMP21, FROST) should NOT publish success events directly to the result queue. The handler (keygen_handler_cggmp21.go) is responsible for publishing the combined result with both ECDSA and EdDSA keys. Sessions should only:

    • Publish FAILURE events to the queue (for immediate error notification)
    • Send success pubkey via externalFinishChan so WaitForFinish() returns
    • Always send to externalFinishChan (even empty string for errors) to prevent blocking

11. Dual keygen architecture: The handleKeyGenEventCGGMP21 function runs both ECDSA (CGGMP21) and EdDSA (FROST) keygen protocols in parallel via goroutines with WaitGroup. Both sessions must complete before the handler publishes the combined result containing both public keys.

FROST Signing Issues (Debugged Jan 2026)

12. FROST config serialization (CRITICAL): frost.TaprootConfig contains crypto types (*curve.Secp256k1Scalar, *curve.Secp256k1Point) that do NOT have JSON marshalers. Using json.Marshal() corrupts the key shares. MUST use CBOR serialization via MarshalFROSTConfig() and UnmarshalFROSTConfig() in frost_config_marshal.go.

13. FROST signing result type: The FROST Taproot signing protocol returns taproot.Signature (which is []byte of 64 bytes), NOT *frost.Signature. The signing_session_frost.go handles this correctly with: s.signature = result.(taproot.Signature).

14. BIP-340/Taproot signature format: FROST signing produces BIP-340 compatible signatures (64 bytes: R_x || s). The taproot.Signature type is already in this format, so no additional conversion is needed in publishResult().

LSS Protocol Issues (Fixed Jan 2026)

15. LSS config serialization (CRITICAL - FIXED): Similar to FROST, lssConfig.Config contains crypto types (curve.Scalar, curve.Point) that do NOT have JSON marshalers. Fixed by implementing MarshalLSSConfig() and UnmarshalLSSConfig() in lss_config_marshal.go using CBOR serialization.

16. LSS capabilities vs CGGMP21: LSS supports dynamic resharing (change T-of-N without reconstructing keys), threshold changes, and adding/removing participants. CGGMP21 only supports refresh (same committee). Both produce valid ECDSA signatures.

Security Audit Findings (Jan 2026)

17. Message authentication: Protocol messages between nodes are not signed. Ed25519 signing code exists but is disabled. Consider re-enabling for production deployments.

18. Deduplication map cleanup: The processing map used for deduplication grows unbounded. Recommend adding TTL-based cleanup for long-running sessions.

19. Protocol timeouts: No timeout enforcement on protocol handlers. Recommend adding context with timeout to prevent indefinite hangs from stalling parties.

🌐 Blockchain Support

Blockchain	Support	Curve	Protocol
Bitcoin (Legacy/SegWit)	✅ Full	secp256k1	CGGMP21/LSS
Bitcoin (Taproot)	✅ Full	secp256k1	FROST
Ethereum/EVM	✅ Full	secp256k1	CGGMP21/LSS
XRPL (XRP Ledger)	✅ Full	secp256k1	CGGMP21/LSS
Lux Network	✅ Full	secp256k1	CGGMP21/LSS
Solana	⚠️ Partial	Ed25519	FROST (Taproot mode)
TON	⚠️ Partial	Ed25519	FROST (Taproot mode)

Note: Solana/TON use Ed25519 natively but our FROST implementation produces Taproot/BIP-340 signatures. Native Ed25519 support requires implementing the Ed25519 FROST variant.

🎯 Best Practices

1. Always backup BadgerDB before major operations
2. Test locally with 3-node setup before production
3. Monitor health via Consul UI (http://localhost:8500)
4. Rotate keys periodically using reshare functionality
5. Use Age encryption for production identities
6. Keep logs for debugging MPC rounds

Context for All AI Assistants

This file (LLM.md) is symlinked as:

• .AGENTS.md
• CLAUDE.md
• QWEN.md
• GEMINI.md

All files reference the same knowledge base. Updates here propagate to all AI systems.

Rules for AI Assistants

1. ALWAYS update LLM.md with significant discoveries
2. NEVER commit symlinked files (.AGENTS.md, CLAUDE.md, etc.) - they're in .gitignore
3. NEVER create random summary files - update THIS file