pulsard

The offline threshold ML-DSA (FIPS-204) signer for the Lux Quasar Pulsar finality lane. It implements warp.PulsarThresholdSigner: a Signer turns a 32-byte subject into one warp.PulsarEvidence carrying a single, standard FIPS-204 ML-DSA-65 signature that the chain verifies with warp.VerifyPulsar.

PRODUCE (offline, here)                  VERIFY (on chain, in warp)
  dealerless nonce DKG, BCC, CEF,  ──►    one FIPS-204 ML-DSA-65 verify
  CSCP, blame, aggregate (TALUS)         (warp.VerifyPulsar)

Honest status

Threshold ML-DSA has no native FIPS-204 construction; the dealerless path is the research-grade TALUS construction (arXiv:2603.22109). This module is deliberately split into what is sound and what is pending:

Part	Status	Where
Service shape (warp.PulsarThresholdSigner)	REAL	signer.go
FIPS-204 ML-DSA-65 primitives (luxfi/crypto, same lib warp verifies with)	REAL	via keyera.go, reference.go
Key-era / group-key records (reuse warp.PulsarKeyEra) + resolver	REAL	keyera.go
Session/nonce plumbing (session id, non-grindable nonce pool)	REAL	nonce.go, session.go
Typed protocol messages + phase state machine	REAL	protocol.go, session.go
Mandatory release gate (re-verify via warp.VerifyPulsar)	REAL	signer.go
Dealerless TALUS threshold crypto	FAIL-CLOSED STUB	engine.go (ErrThresholdMLDSAUnimplemented), design in docs/talus-design.tex
Trusted-dealer single-party engine	REFERENCE / DEV-TEST FOOTGUN	reference.go

No fake threshold math is shipped. The default engine fails closed; the only engine that produces a signature is the clearly-labelled, non-threshold ReferenceDealer, which exists solely to prove the verify integration.

The boundary guarantee

Signer.ThresholdSign never returns evidence that does not verify: whatever engine is plugged in, the signature is re-checked with warp.VerifyPulsar (the chain's own verifier) before it leaves the process. Emitted-evidence correctness is a property of pulsard, independent of the engine.

Build & test

SDKROOT="$(xcrun --show-sdk-path)" GOWORK=off GOFLAGS=-mod=mod GOPRIVATE=github.com/lux-private/* \
  go build ./... && go test ./...

Demo (dev/test footgun)

go run ./cmd/pulsard -mode reference   # produces a real group sig, VERIFIED via warp.VerifyPulsar
go run ./cmd/pulsard -mode threshold   # FAIL-CLOSED: ErrThresholdMLDSAUnimplemented (as designed)

Wiring a real engine

A concrete dealerless engine (candidate: github.com/luxfi/pulsar) may be registered behind the ThresholdEngine SPI only after the interop and trust contracts in docs/talus-design.tex (§7) are established and reviewed: interop under mldsa65.Verify, dealerless keygen, malicious-secure CSCP, dual-PQ key independence, and a bounded transcript-distribution caveat.