Magnetar v1.2 --- SLH-DSA (FIPS 205) for Lux

Magnetar v1.2 ships ONE construction surface to each of the two deployment regimes Lux ecosystem chains need, with the strict-atom Combine path closing MAGNETAR-STRICT-ATOM-V11 and the dealerless PVSS-DKG closing MAGNETAR-PVSS-DKG-V11:

Regime	Construction	Where it lives
Public-BFT consensus on Lux L1/L2 (mainnet, testnet, devnet, white-label)	Per-validator standalone --- each validator holds its own FIPS 205 keypair, signs independently, consensus collects N signatures into a ValidatorAggregateCert	ref/go/pkg/magnetar/standalone.go
Permissionless t-of-n threshold for verifier-side single-signature certificates	THBS-SE (strict-atom Combine) --- t-of-n committee, slot-bound commit-and-reveal, anyone-can-combine public combiner, Magnetar-internal FIPS 205 sec 5--sec 8 walk with no named transient seed binder	ref/go/pkg/magnetar/thbsse.go + thbsse_field.go + thbsse_assemble.go + slhdsa_internal.go

Both produce FIPS 205 wire bytes that an unmodified verifier accepts.

Per-validator standalone (public-BFT primary)

sk, pk, _ := magnetar.PerValidatorKeypair(params, rng)
sig, _    := magnetar.ValidatorSign(sk, rng, message)
// ... collected at the consensus layer ...
cert, _   := magnetar.BuildAggregateCert(params, signers, pubkeys, sigs)
valid, _  := magnetar.VerifyAggregateCert(cert, message, knownValidators)

No DKG, no shared seed, no aggregator-in-TCB. Wire size grows linearly with the quorum (N x |sigma|). The Z-Chain Groth16 rollup compresses the cert to ~192 bytes for long-term storage; the rollup is a separate primitive (lux-zchain spec).

THBS-SE (permissionless threshold)

key, _   := magnetar.NewThbsSeKey(params, t, committee, setupRng)
// Per-party Round-1 / Round-2 over the slot binding ...
r1i, r2i, _ := magnetar.ThbsSeRound1(params, key.Shares[i], binding, msg, guard, rng)
// ... any peer (the "public combiner") collects t valid r1/r2 pairs ...
sig, ev, _  := magnetar.Combine(magnetar.ThbsSeCombineInput{
    Key: key, Binding: binding, Message: msg, Round1: r1s, Round2: r2s,
})
// sig.Bytes is canonical FIPS 205; verifies under unmodified circl.slhdsa.Verify.

Setup --- two equivalent paths

Dealer setup (KAT-reproducible). NewThbsSeKey samples a master, byte-shares it via Shamir over GF(257), and zeroizes the master before return. The dealer machine is in the TCB FOR SETUP ONLY; once the function returns, no party (including the dealer) holds the master. Recommended for foundation-HSM single-host bootstrap and KAT replay.

Dealerless PVSS-DKG setup (no trusted dealer). Each committee party runs NewPVSSPartyState independently, publishes a PublicContribution (per-coefficient hash commitments only), distributes private share rows over authenticated channels, and publishes a RevealMsg at Round 2. Any third party collates the public payloads into a PVSSTranscript and invokes NewThbsSeKeyFromDealerlessDKG to assemble the canonical ThbsSeKey:

// Each party i runs in its own process.
state_i, _ := magnetar.NewPVSSPartyState(params, t, committee, uint32(i+1), rng)
contrib_i  := state_i.PublicContribution()  // broadcast publicly
share_to_j, _ := state_i.ShareTo(uint32(j+1))  // send privately to j
reveal_i := state_i.RevealMsg()              // broadcast publicly at Round 2

// Any auditor (or any party) collates the public-form transcript
// and assembles the canonical ThbsSeKey.
transcript := &magnetar.PVSSTranscript{
    Params: params, Committee: committee, Threshold: t,
    Contributions: contribs, Reveals: reveals,
    ReceivedShares: receivedShares, SetupTr: setupTr,
}
key, _ := magnetar.NewThbsSeKeyFromDealerlessDKG(transcript)
// key is byte-shape identical to the dealer-path output for the
// implicit master M = sum_{i in Q} m_i mod 257 byte-wise.

The dealerless path enforces the hard invariant: no party (and no transient dealer) ever holds the master byte vector at any time during setup. The implicit master is only materialised inside the deriveDKGPublicKey closure (named lagrangeScratch, zeroized at closure exit) when an auditor invokes VerifyDKGTranscript to derive the public key.

For reference, the RunDKGSimulation helper runs the full n-party protocol in a single test process (every party's state in one heap) for KAT replay and benchmark purposes; production deployments should run each party in its own process.

Hard invariant (THBS-SE construction): a revealed value is allowed ONLY if it is also present in the final SLH-DSA signature.

• ALLOWED reveals: the per-round mask r_i, the masked share s'_i = share_i XOR r_i, the public commit hash, the final FIPS 205 signature bytes.
• FORBIDDEN reveals: SK.seed in any party-local persistent form; SK.prf; future-slot share material. The slot guard refuses any same-slot re-emission, and the share envelope is per-slot.

No-aggregator property: The public combiner is a PURE function of its inputs. Any peer --- validator, block proposer, RPC node, passive watcher --- can run Combine. There is no privileged aggregator role and no host in the TCB at sign time. (The strict-atom Combine path at v1.1 closed the residual transient-seed-at-combiner gap; see BLOCKERS.md::MAGNETAR-STRICT-ATOM-V11 for the closure summary.)

No-trusted-dealer property: The PVSS-DKG setup path (NewThbsSeKeyFromDealerlessDKG, v1.2) eliminates the trusted dealer from setup. No party (and no transient dealer) ever holds the master byte vector at any time during setup. See BLOCKERS.md::MAGNETAR-PVSS-DKG-V11 for the closure summary and pvss_dkg.go for the construction.

Slot binding: every signature is bound to (chain_id, epoch, slot, height, committee_id, message_domain). The binding flows into the cSHAKE256 commit transcript AND into the FIPS 205 ctx string at sign time, so a verifier holding the slot tuple derives ctx independently and routes through unmodified slhdsa.Verify.

Slashing evidence: a party that signs two distinct messages at the same slot emits a ThbsSeEquivocationError carrying a wire- shaped ThbsSeEvidence blob that any third party can verify via VerifyThbsSeEvidence --- pure function, no committee state required. Malformed shares produce typed ThbsSeShareEvidence blobs verified via VerifyThbsSeShareEvidence.

Over-selected committee: with (n, t) and n > t, up to n - t silent withholders are tolerated. Any t valid Round-2 reveals produce byte-equal final signatures.

Why per-validator standalone is the public-BFT default

SLH-DSA is hash-based; it has no algebraic structure that admits FROST-style linear share-aggregation. The literature confirms:

• Cozzo and Smart, EUROCRYPT 2019 Sharing the LUOV: every internal SHAKE/SHA-2 evaluation in an HBS scheme is a non-linear function of the secret seed.
• Bonte, Smart and Tan 2023 Threshold SPHINCS+: exhaustive infeasibility analysis. There is no efficient t-of-n SLH-DSA scheme producing a single FIPS 205-shaped signature without either (a) reconstructing the seed in some combiner process or (b) running full MPC over the SHA-256/SHAKE hash tree (multi-second per signature, multi-megabyte of comms).

THBS-SE chooses (a) with a PUBLIC COMBINER --- anyone-can-combine, no host in TCB. The per-validator standalone path sidesteps (a) and (b) entirely by emitting N independent signatures.

Status

Field	Value
Standard	FIPS 205 SLH-DSA (single-party + per-validator standalone aggregate + THBS-SE permissionless threshold)
Constructions	2 (per-validator standalone, THBS-SE)
Reference implementation	ref/go/pkg/magnetar/ --- pure Go, depends on cloudflare/circl/sign/slhdsa v1.6.3
KAT vectors	vectors/{keygen,sign,verify,thbsse-sign}.json (deterministic regeneration)
Wire identity	Both Magnetar primitives emit byte-identical FIPS 205 signatures; any unmodified slhdsa verifier accepts
Tag	v1.2.0
Cert-profile role	Polaris profile in luxfi/quasar (hash-based leg of the maximum-assurance cross-family PQ profile)
Sibling primitives	Pulsar (FIPS 204 M-LWE), Corona (R-LWE) --- algorithmically distinct families

Headline tests

cd ref/go && GOWORK=off go test -count=1 -short -timeout 600s ./pkg/magnetar/...

• TestMagnetar_Wire_FIPS205Verifiable (wire_test.go) --- pins byte-identity between ValidatorSign output and unmodified cloudflare/circl/sign/slhdsa.Verify across all 3 SHAKE modes.
• TestThbsSE_Wire_FIPS205Verifiable (thbsse_test.go) --- pins the same identity for the THBS-SE public combiner output.
• TestThbsSE_RejectSeedReveal, TestThbsSE_RejectUnselectedFORS, TestThbsSE_RejectUnselectedWOTS, TestThbsSE_SlotReuseRejected, TestThbsSE_OverselectedCommittee, TestThbsSE_SlotBindingDomainSeparation --- the 6 invariant gates for the THBS-SE construction.
• TestPVSS_DKG_NoSinglePartyHoldsMaster, TestPVSS_DKG_ByteCompatWithDealerPath, TestPVSS_DKG_AdversarialReveals, TestPVSS_DKG_RobustnessAgainstMaliciousCommitments, TestPVSS_DKG_EndToEnd_SignAndVerify --- the 5 invariant gates for the dealerless PVSS-DKG setup path (v1.2).
• BenchmarkThbsSE_Sign_5of7/Magnetar-SHAKE-192f --- end-to-end per-signature wall-clock at < 100 ms/op on Apple M1.
• TestKAT_ThbsSe --- deterministic vector replay at (n=7, t=4) x 3 modes x 3 messages.

Operator-controlled MPC custody

For deployments where an HSM-attested host is in the TCB by deployment policy (e.g. M-Chain bridge custody, A-Chain confidential compute), TEE-attestation-gated variants ship under luxfi/threshold/protocols/{slhdsa,mldsa,rlwe}-tee via the lux/mpc sibling tree --- NOT in this package. Magnetar's role is the public-BFT and permissionless-threshold surface; the operator- controlled variants are decomplected into their own primitive slot.

Where this is used

The hash-based leg of the Polaris cert profile in luxfi/quasar --- the maximum-assurance cross-family profile pairing lattice PQ (Pulsar M-LWE + Corona R-LWE) with hash-based PQ (Magnetar SLH-DSA).

Documents

• SPEC.md --- normative construction specification.
• THBS-SPEC.md --- THBS-SE normative spec (slot binding, commit-reveal, public-combiner, evidence).
• CHANGELOG.md --- release-by-release framing.
• DEPLOYMENT-RUNBOOK.md --- public-BFT default + the v1.0 honest open item (transient seed reconstruction at the public combiner).
• BLOCKERS.md --- the v1.1 roadmap (strict-atom-assembly path).
• CRYPTOGRAPHER-SIGN-OFF.md --- internal review trail.
• TRUSTED-COMPUTING-BASE.md --- TCB enumeration.
• PROOF-CLAIMS.md --- proof-roadmap inventory.
• AXIOM-INVENTORY.md --- assumed-axiom enumeration.
• FIPS-TRACEABILITY.md --- line-by-line FIPS 205 conformance trace.
• PATENTS.md --- patent-status notes.
• LICENSING.md --- license terms.
• SUBMISSION.md / NIST-SUBMISSION.md / SUBMISSION-STATUS.md --- NIST MPTC submission framework.

Build

cd ref/go && GOWORK=off go build ./...
cd ref/go && GOWORK=off go test -count=1 -short -timeout 600s ./pkg/magnetar/...
cd ref/go && GOWORK=off go test -count=1 -race -short -timeout 600s ./pkg/magnetar/...

Citations

• NIST FIPS 205 (2024). Stateless Hash-Based Digital Signature Standard.
• Cozzo, D. and Smart, N. P. (2019). Sharing the LUOV. EUROCRYPT.
• Bonte, C., Smart, N. P. and Tan, T. (2023). Threshold SPHINCS+: Practical Threshold Signatures from a Stateless Hash-Based Signature.
• McGrew, D., Wallace, C. and Whyte, W. (2019). Threshold Hash-Based Signatures. IACR ePrint 2019/793.
• Schoenmakers, B. (1999). A simple publicly verifiable secret sharing scheme and its application to electronic voting. CRYPTO.
• Shamir, A. (1979). How to share a secret. Communications of the ACM.