threshold/protocols/slhdsa-tee/README.md

slhdsa-tee

Operator-controlled SLH-DSA threshold signing via TEE-gated master-seed reconstruction.

What this is

A composable Go package that produces FIPS 205 SLH-DSA signatures gated on:

1. A verifiable hardware TEE attestation (AMD SEV-SNP, Intel TDX, NVIDIA NRAS) chain-validated by github.com/luxfi/mpc/cc/attest.
2. A KMS release-gate (github.com/luxfi/mpc/pkg/kms.ReleaseGate) that pins the worker's RIM digest + hardware fingerprint and binds a single-use challenge nonce per request.
3. An out-of-band human or programmatic approval signature (github.com/luxfi/mpc/pkg/approval.ApprovalProvider).
4. An HSM-resident wrap-key store (github.com/luxfi/mpc/pkg/hsm.Provider) so the master SLH-DSA seed lives sealed-at-rest and is only ever unwrapped inside the attested TEE.

Output is byte-identical to single-party FIPS 205 SignDeterministic on the same (seed-derived sk, msg, ctx) tuple. Any verifier holding the published MAGG-framed group public key validates with magnetar.VerifyBytes — no awareness of the threshold or TEE substrate is required.

When to use this

• M-Chain bridge custody: an operator holds the bridge's signing key inside a SEV-SNP / TDX TEE. Per-redemption sign calls require an attestation envelope plus an executive approval. The master seed never leaves the HSM in plaintext outside the attested TEE context.
• A-Chain confidential-compute oracle: an oracle node produces SLH-DSA attestations over confidential model outputs. The output is gated on the worker's RIM matching a known-good measurement allowlist.

When NOT to use this

• Public-BFT consensus: use the per-validator standalone magnetar.ValidatorSign path (canonical v0.5+). No DKG, no dealer, no aggregator-in-TCB.
• Permissionless threshold custody: use magnetar.Combine (THBS-SE, v0.1 reveal-and-aggregate) — no party ever holds the master seed, so there is no TCB to attest.
• Test / dev with no TEE hardware available: use magnetar.GenerateKey + magnetar.Sign directly.

Decision matrix

Use case	Primitive
Public-BFT validator	magnetar.ValidatorSign (PRIMARY)
Permissionless N-of-N custody, no party holds seed	magnetar.Combine (THBS-SE)
Institutional custody with attested release	slhdsa-tee.Signer.Sign (THIS)
Single-party / dev	magnetar.Sign

Layering

caller (operator daemon, bridge node, custody orchestrator)
  └── slhdsatee.Signer.Sign(ctx, env, jobID, msg, signCtx)
        ├── approval.ApprovalProvider.ApproveIntent  (out-of-band gate)
        ├── kms.ReleaseGate.Issue / Release          (TEE-gated wrap key)
        │     └── cc/attest.Dispatch                  (vendor chain verify)
        ├── hsm.Provider.GetKey                       (wrapped seed at rest)
        ├── magnetar.KeyFromSeed → magnetar.Sign      (FIPS 205 emit)
        └── hsm.Provider.Sign                         (audit signature)

Each step is independently complete and replaceable.

Threat model

• Compromised operator binary outside TEE: refused — no valid attestation possible.
• Forged attestation envelope (chain-invalid): refused at cc/attest.Dispatch → kms.ErrAttestationChain.
• Replay of an old sealed key: refused — AAD binds (epoch, jobID, teePub, issuedNonce).
• Coerced approver: detectable in the receipt's audit signature trail.
• Stolen master seed at rest: protected by HSM root-of-trust (AWS KMS, Azure Key Vault, GCP Cloud KMS, YubiHSM, Zymbit, file with age-encryption).

Example

import (
    slhdsatee "github.com/luxfi/threshold/protocols/slhdsa-tee"
    magnetar "github.com/luxfi/magnetar/ref/go/pkg/magnetar"
    "github.com/luxfi/mpc/pkg/kms"
    "github.com/luxfi/mpc/pkg/hsm"
    "github.com/luxfi/mpc/pkg/approval"
)

policy := kms.NewReleasePolicyStrict([][32]byte{knownRIM}, [][32]byte{knownHW})
store := kms.NewMemoryNonceStore() // or DatabaseNonceStore in prod
gate, _ := kms.NewLocalReleaseGate(policy, store, rootKey)
hsmP, _ := hsm.NewAWSProvider(awsCfg)
appr, _ := approval.NewProvider("webauthn", webauthnCfg)

cfg := slhdsatee.Config{
    Mode:             magnetar.ModeM192s,
    RequiredRIM:      policy.RequiredRIM,
    AllowedHardware:  policy.AllowedHardware,
    RequireSEVSNP:    true,
    KMSKeyID:         "arn:aws:kms:us-east-1:...:key/...",
    WrappedSeedKeyID: "lux-custody-master-seed",
    ApprovalRequired: true,
    ApproverID:       "[email protected]",
}
signer, _ := slhdsatee.New(gate, hsmP, appr, cfg)

env := &slhdsatee.Envelope{
    Kind:          attest.KindSEVSNP,
    EvidenceBytes: liveAttestationBytes,
    RIM:           knownRIM,
    Hardware:      knownHW,
    TEEPub:        workerTEEPub,
}
jobID, _ := slhdsatee.FreshJobID()
sig, receipt, err := signer.Sign(ctx, env, jobID, msg, nil)

Dispatcher wiring

The pkg/thresholdd JSON-RPC dispatcher gains a Sign_TEE method on the magnetar scheme that calls this package. The default Sign method remains permissionless (per-validator standalone).