THRESHOLD SIGNING · POST-QUANTUM

Multi-Party Threshold Signing.
Zero Single Points of Failure.

Multi-party key generation, signing, and resharing with Dilithium (ML-DSA) attestation. Configurable N-of-M threshold. No single party ever holds the complete key.

Get API Key → API Docs Compare H33-3-Key

N-of-M

Threshold

ML-DSA

Attestation

Zero

Single Point

Credits/Session

PIPELINE

Four-Phase MPC Session Lifecycle

Create a session, collect contributions from each party, finalize with threshold combination, and receive a Dilithium-attested result. All contributions are zeroed from memory on completion.

1 Create

Session Init

Define the operation (Sign, KeyGen, or Reshare), set the N-of-M threshold, and specify participating parties. Session ID returned immediately.

Sign KeyGen Reshare N-of-M

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2 Contribute

Party Shares

Each party submits their key share or signature fragment. Contributions are validated and stored with Zeroize-on-drop memory safety. Multi-round support for complex protocols.

Per-party Zeroize Multi-round

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3 Finalize

Threshold Combine

Once threshold is met, contributions are combined. Sign operations proxy to gRPC gateway. KeyGen and Reshare combine locally via SHA3 hash. Result is Dilithium-signed.

gRPC proxy SHA3 Dilithium

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4 Attested

PQ-Signed Result

Final result carries a Dilithium (ML-DSA) signature attesting the computation was performed correctly. All party contributions are zeroed from memory. Session marked complete.

ML-DSA FIPS 204 Memory-safe

MPC Session

8 credits per session

Dilithium attestation included

SECURITY

MPC Security Architecture

Every MPC session is memory-safe, post-quantum attested, and designed with zero persistence. Party contributions never touch disk.

Parameter	Value
Operations	Sign, KeyGen, Reshare
Threshold	Configurable N-of-M
Attestation	Dilithium (ML-DSA, NIST PQC)
Session storage	In-memory DashMap (zero persistence)
Party contributions	Zeroize-on-drop (memory-safe)
Sign gateway	gRPC proxy to MPC backend
Post-quantum	Dilithium-5 attestation (NIST Level 5)

API

MPC Session API

Four endpoints for the complete MPC lifecycle. Create, contribute, finalize, and query session status. All endpoints authenticated via API key.

MPC Session — 8 credits/session

Full multi-party computation session including creation, all party contributions, threshold finalization, and Dilithium attestation of the result.

POST/v1/mpc/session/create

POST/v1/mpc/session/{id}/contribute

POST/v1/mpc/session/{id}/finalize

GET/v1/mpc/session/{id}/status

Example — Create a 2-of-3 signing session

curl -X POST https://api.h33.ai/v1/mpc/session/create \
  -H "Authorization: Bearer $H33_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "operation": "Sign",
    "threshold": 2,
    "total_parties": 3,
    "party_ids": ["party_alice", "party_bob", "party_carol"],
    "message_hash": "base64..."
  }'

# Response:
# {
#   "session_id": "mpc_abc123",
#   "phase": "AwaitingContributions",
#   "contributions_needed": 2
# }

Example — Contribute a key share

curl -X POST https://api.h33.ai/v1/mpc/session/mpc_abc123/contribute \
  -H "Authorization: Bearer $H33_API_KEY" \
  -d '{
    "party_id": "party_alice",
    "round": 1,
    "payload": "base64_key_share..."
  }'

Use Cases

Distributed Trust, Zero Single Points

H33-MPC eliminates single points of failure in key management. No single party ever holds the complete signing key — threshold combination is required for every operation.

Distributed Custody

No single key holder. Split signing authority across multiple custodians, geographies, or compliance domains. A compromised party cannot sign alone. Ideal for institutional digital asset custody.

Multi-Sig Governance

DAO treasury operations, board approvals, and multi-stakeholder governance. Configurable 2-of-3, 3-of-5, or any N-of-M threshold. Every finalized action carries Dilithium attestation.

Key Rotation Without Downtime

Reshare operation redistributes key shares to a new set of parties without ever reconstructing the full key. Zero downtime during rotation. Old shares become cryptographically useless.

Regulatory Compliance

Segregation of signing authority meets regulatory requirements for financial services, healthcare, and government. Auditable session logs with post-quantum attestation on every operation.

Multi-Party Threshold Signing.Zero Single Points of Failure.

Four-Phase MPC Session Lifecycle

MPC Security Architecture

MPC Session API

Distributed Trust, Zero Single Points

Start Building With H33-MPC

Multi-Party Threshold Signing.
Zero Single Points of Failure.