zeekayandHanzo Dev
f01758f3a8
Signing used the key's whole participant set, so a 3-of-5 key signed with five parties. That works, but it never exercises the quorum: a key that was accidentally degree-3 would sign identically, which is precisely the failure this VM exists to catch. RunSign now selects K signers by ranking participants on H(tag ‖ keyID ‖ digest ‖ party) and taking the first K. The selection is a pure function of the task, so every node — signer or not — computes the same quorum and the same ceremony id with no election. Ranking by digest rather than taking the first K in canonical order spreads signing across the committee instead of loading the same K parties for every transfer, and stops an adversary steering which subset signs a message it does not control. Nodes outside the quorum return ErrNotInQuorum and verify the result like any other validator. Verify deliberately does not pin WHICH K-subset signed. The signature verifies under the group key or it does not, and an adversary who can produce one already holds K shares, so constraining the subset buys no security while leaving it open lets availability-aware reselection ship later without a consensus change. TestBridgeCustody_ThreeOfFive is the gate: five validators run a real CGGMP21 DKG over the gossip fabric at degree 2, exactly three sign, two decline, the signature verifies under the group key, a block carrying it is verified and accepted by all five — including the two that never touched the ceremony — and every node ends on the same state root. Co-authored-by: Hanzo Dev <[email protected]>
ThresholdVM
ThresholdVM is a Go library, not a chain.
Per LP-134 (Lux Chain Topology) and LP-7050 (Supersession Map), T-Chain is fully removed with zero remainder. Its concerns decompose onto existing chains, each of which consumes this library substrate:
- M-Chain (
mpcvm, LP-7100) — bridge custody for external wallets, threshold signing ceremonies (CGGMP21 / FROST / Pulsar-general). Owns all threshold signing. - F-Chain (
fhevm, LP-8200) — TFHE keygen, encrypted EVM, threshold decrypt, confidential compute. Owns all encrypted computation.
chains/mpcvm/ is the shared library these two chains import in
process — it is not itself a chain and has no genesis, no validators, no
block production. There is no teleportvm and no "T-Chain": teleport
IS bridgevm (B-Chain, LP-6000). Any live identifier still naming "T-Chain",
"ThresholdVM-as-a-chain", or "teleportvm" is stale.
+--------------------------------+
| ThresholdVM |
| (ceremony state machine, |
| share envelope, lane API, |
| subject binding) |
+----------------+---------------+
|
+-------------------+-------------------+
| |
+--------v--------+ +--------v--------+
| M-Chain | | F-Chain |
| (MPC: CGGMP21, | | (FHE: TFHE, |
| FROST, | | bootstrap-key |
| Corona-gen) | --bootstrap key--> | gen, encrypted |
| | | EVM) |
+-----------------+ +-----------------+
ceremony_root: ceremony_root:
mchain_ceremony_root fchain_fhe_root
block time ~500ms block time ~2s
sign-oriented compute-oriented
What this directory contains
| Path | Role |
|---|---|
types/ |
Ceremony, Participant, Share, Proof — pure data types, no chain logic |
protocol/ |
Protocol-specific verifier interfaces (impl ships with the chain that uses it) |
cert/ |
QuasarCertLane integration: lane registration + certificate-subject binding |
runtime/ |
MChainAdapter and FChainAdapter interfaces the two chains implement |
docs/ |
Architecture + per-chain integration notes |
What this directory is not
- Not a Lux VM. There is no
factory.goexposed tochains.Manager. - Not a chain ID. M-Chain and F-Chain are the chains; they have their own validator sets, ceremony roots, and block cadence.
- Not a registry of secrets, keys, or signed material. State lives on M-Chain or F-Chain, never here.
Why split
LP-134 deprecates LP-5013 ("T-Chain MPC Custody"). T-Chain previously mixed MPC ceremonies and FHE compute under one validator set, one ceremony root, one block cadence. Sign-oriented (sub-second, latency critical) and compute-oriented (multi-second, throughput critical) workloads have incompatible scaling profiles. Splitting them lets each scale on its own validator set.
The substrate stays one piece because the ceremony state machine is
identical across both: registered participants → round 1 commitments →
round 2 shares → finalized cert. Only the per-protocol payload
(carried by (offset, len) indirection in the share envelope) differs.
Permissionless participation
Both M-Chain and F-Chain inherit P-Chain's permissionless validator model. Anyone with stake on P-Chain can delegate to the M-Chain or F-Chain validator subset (or both). No allowlist. No central authority. Bitcoin-like decentralization carries through — the threshold scheme itself enforces honest-majority safety, the chain enforces liveness.
Cross-chain handoff
When M-Chain finishes a ceremony whose output feeds F-Chain (e.g., a TFHE bootstrap key generated by FROST DKG on M-Chain), the output crosses via a CertLane artifact:
- M-Chain finalizes ceremony, emits cert with lane
MChainFROSTandmchain_ceremony_rootupdated. - F-Chain consumes the artifact via its
FChainBootstraplane, binds it intofchain_fhe_root. - Quasar 3.0's
certificate_subjectbinds both roots in the same round, making cross-chain replay structurally impossible.
The handoff envelope is defined in cert/lane.go; the typed adapter
in runtime/.
Migration from T-Chain
LP-5013 is deprecated. The legacy chain at chains/mpcvm/ (this
directory's vm.go, block.go, factory.go, fhe/, cmd/) hosts
the migration shims that route legacy TChain* cert lanes to the
appropriate MChain* / FChain* verifiers during the one-epoch grace
window. After the grace window closes, the shims are removed and only
the substrate (this README's directory tree) remains.
Activation
ThresholdVM substrate activates with Quasar 3.0 on 2025-12-25, alongside the M-Chain and F-Chain genesis events. Versions before that date target the legacy T-Chain layout.
References
| LP | Topic |
|---|---|
| LP-019 | Threshold MPC for Bridge Signing (M-Chain protocols) |
| LP-013 | FHE on GPU (F-Chain compute) |
| LP-076 | Universal Threshold Cryptography Framework |
| LP-134 | Lux Chain Topology — defines the M/F split |
| LP-132 | QuasarGPU Execution Adapter — lane verifiers run here |
| LP-020 | Quasar Consensus 3.0 — certificate_subject binding |
License
Copyright (C) 2019-2025 Lux Industries Inc. MIT licensed.