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https://github.com/luxfi/fhe.git
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feat(threshold): t-of-n threshold FHE service layer
Adds threshold/ package implementing the MPCVM v0.62 four-kernel template for partial decryption, share verification, and aggregate decryption of FHE ciphertexts. Three service interfaces (PartialDecryptService, ShareVerifyService, ShareAggregateService) compose existing FHE primitives with party-aware logic. Every wire object binds to a canonical sha256 root; the transcript root is keccak256 to match the Quasar precompile path. Includes a placeholder HMAC-bound noise proof. PRODUCTION REQUIRES replacement with a CDS sigma protocol (Cramer-Damgard-Schoenmakers disjunctive sigma proof made non-interactive via Fiat-Shamir over the share transcript). The verification interface is in place; only the inner buildNoiseProof body changes. Tests: 14/14 pass. Covers 2-of-3 + 3-of-5 happy paths, insufficient shares, tampered share data, bad noise proof, replay protection, wrong-ciphertext rejection, transcript root order invariance, and noise proof version tagging.
This commit is contained in:
Hanzo AI
@@ -0,0 +1,309 @@
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// Share aggregation — collects ≥t shares, verifies each, combines into
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// the threshold-decryption plaintext, emits canonical roots.
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//
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// Aggregation is the second-half of the four-kernel template applied to
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// threshold decryption:
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//
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// apply — collect-and-dedupe shares (per-party ordering)
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// sweep — re-verify every share (transcript + noise)
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// compute_leaves — per-share contribution to the recovered plaintext
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// compose_root — Merkle ShareRoot + AggregateRoot + transcript root
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//
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// The package targets the BFV/CKKS-style sum-then-round threshold
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// scheme by default — partial decryptions sum across parties and the
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// aggregator rounds the result to the plaintext modulus. The TFHE
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// branch (Z_2 sum, no rounding) is selected by the toy test scheme and
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// is byte-equivalent at the canonical-encoding level.
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//
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// Copyright (c) 2026, Lux Industries Inc.
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// SPDX-License-Identifier: BSD-3-Clause
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package threshold
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import (
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"context"
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"errors"
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"sort"
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)
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// ErrTooFewShares indicates the aggregator was supplied fewer than
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// `threshold` shares. Returned with FHEThresholdResult.Status =
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// StatusInsufficientShares.
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var ErrTooFewShares = errors.New("threshold: too few shares for aggregation")
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// ErrDuplicatePartyID indicates two shares carried the same PartyID.
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// Caught before aggregation so a single misbehaving party cannot inflate
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// its weight.
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var ErrDuplicatePartyID = errors.New("threshold: duplicate party id in shares")
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// ShareAggregator is the default in-process ShareAggregateService. The
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// Verifier field is the share-verification path used before combining.
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// PartyKeys, when populated, switches verification to the
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// VerifyShareWithKey path — the only path that succeeds against the
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// placeholder noise proof, and so the only path that runs in committee
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// self-check mode today.
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type ShareAggregator struct {
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Verifier *ShareVerifier
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// PartyKeys keys verifiers by PartyID. When non-nil the aggregator
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// uses VerifyShareWithKey for the matching share; otherwise it
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// falls back to the public-key VerifyShare path.
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//
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// Production deployments populate PartyKeys for the committee
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// self-check leg and rely on the producer-side noise proof for
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// cross-committee verification.
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PartyKeys map[uint32]KeyShare
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// PartyPubKeys is the public-key alternative to PartyKeys. When
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// neither is populated, verification is restricted to the cheap
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// structural checks (root + ciphertext id) — used by tests and by
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// debug paths only.
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PartyPubKeys map[uint32]PublicKey
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}
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// NewShareAggregator returns a default ShareAggregator.
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func NewShareAggregator() *ShareAggregator {
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return &ShareAggregator{Verifier: NewShareVerifier()}
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}
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// Aggregate verifies and combines shares.
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//
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// On success: returns FHEThresholdResult{Status=StatusOK, ...} with all
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// roots populated, plus the recovered plaintext bytes.
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//
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// On insufficient-shares failure: returns
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// {Status=StatusInsufficientShares, ...} with the partial roots populated
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// for the shares received and ErrTooFewShares.
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//
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// On per-share verification failure: returns the matching status
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// (StatusShareRootMismatch / StatusNoiseProofFailed / StatusUnknownParty)
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// and ErrNoiseProofVerify or ErrShareRootMismatch — caller decides
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// whether to retry with replacement shares.
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func (a *ShareAggregator) Aggregate(
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ctx context.Context,
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ciphertext FHECiphertext,
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shares []FHEThresholdShare,
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threshold uint32,
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sessionID [32]byte,
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) (FHEThresholdResult, []byte, error) {
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if err := ctx.Err(); err != nil {
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return FHEThresholdResult{}, nil, err
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}
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// apply: order shares canonically (ascending PartyID) and dedupe.
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sorted, err := orderShares(shares)
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if err != nil {
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return FHEThresholdResult{
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CiphertextRoot: ciphertext.ID,
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Threshold: threshold,
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Status: StatusUnknownParty,
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}, nil, err
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}
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// sweep: per-share verification.
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verifier := a.Verifier
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if verifier == nil {
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verifier = NewShareVerifier()
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}
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valid := make([]FHEThresholdShare, 0, len(sorted))
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for i := range sorted {
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s := sorted[i]
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ok, verr := a.verifyOne(ctx, verifier, s, ciphertext, sessionID)
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if verr != nil {
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return FHEThresholdResult{
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CiphertextRoot: ciphertext.ID,
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ShareRoot: merkleShareRoot(sorted[:i]),
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PartyCount: uint32(i),
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Threshold: threshold,
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Status: classifyVerifyErr(verr),
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}, nil, verr
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}
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if ok {
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valid = append(valid, s)
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}
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}
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if uint32(len(valid)) < threshold {
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return FHEThresholdResult{
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CiphertextRoot: ciphertext.ID,
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ShareRoot: merkleShareRoot(valid),
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PartyCount: uint32(len(valid)),
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Threshold: threshold,
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Status: StatusInsufficientShares,
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}, nil, ErrTooFewShares
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}
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// compute_leaves: per-share contribution. The toy threshold
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// scheme XOR-aggregates the masked-secret slices across the t
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// shares; the noise terms cancel modulo two (TFHE) or modulo q
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// after rounding (BFV/CKKS). The byte-vector path matches the
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// XOR-combine the unit tests exercise.
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plaintext := combineShares(valid[:threshold], ciphertext)
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// compose_root: AggregateRoot + ShareRoot + transcript.
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result := FHEThresholdResult{
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CiphertextRoot: ciphertext.ID,
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ShareRoot: merkleShareRoot(valid[:threshold]),
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AggregateRoot: computeAggregateRoot(plaintext, threshold, threshold),
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PartyCount: threshold,
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Threshold: threshold,
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Status: StatusOK,
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}
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return result, plaintext, nil
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}
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// verifyOne dispatches to the right verification path based on what
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// keys the aggregator has been configured with.
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func (a *ShareAggregator) verifyOne(
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ctx context.Context,
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v *ShareVerifier,
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share FHEThresholdShare,
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ciphertext FHECiphertext,
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sessionID [32]byte,
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) (bool, error) {
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if a.PartyKeys != nil {
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if k, ok := a.PartyKeys[share.PartyID]; ok {
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return v.VerifyShareWithKey(ctx, share, ciphertext, k, sessionID)
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}
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return false, ErrPartyIDMismatch
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}
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if a.PartyPubKeys != nil {
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if pk, ok := a.PartyPubKeys[share.PartyID]; ok {
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return v.VerifyShare(ctx, share, ciphertext, pk, sessionID)
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}
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return false, ErrPartyIDMismatch
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}
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// No keys configured: structural-only checks. The verifier still
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// re-derives ShareRoot and compares CiphertextID; only the noise
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// proof step is skipped.
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if share.CiphertextID != ciphertext.ID {
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return false, ErrCiphertextIDMismatch
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}
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expected := computeShareRoot(share, sessionID)
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if expected != share.ShareRoot {
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return false, ErrShareRootMismatch
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}
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return true, nil
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}
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// orderShares sorts shares ascending by PartyID and rejects duplicates.
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func orderShares(shares []FHEThresholdShare) ([]FHEThresholdShare, error) {
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out := make([]FHEThresholdShare, len(shares))
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copy(out, shares)
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sort.Slice(out, func(i, j int) bool {
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return out[i].PartyID < out[j].PartyID
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})
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for i := 1; i < len(out); i++ {
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if out[i].PartyID == out[i-1].PartyID {
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return nil, ErrDuplicatePartyID
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}
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}
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return out, nil
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}
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// classifyVerifyErr maps a verification error to FHEStatus.
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func classifyVerifyErr(err error) FHEStatus {
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switch {
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case errors.Is(err, ErrShareRootMismatch):
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return StatusShareRootMismatch
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case errors.Is(err, ErrCiphertextIDMismatch):
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return StatusInvalidCiphertext
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case errors.Is(err, ErrPartyIDMismatch):
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return StatusUnknownParty
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case errors.Is(err, ErrNoiseProofVerify):
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return StatusNoiseProofFailed
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default:
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return StatusNoiseProofFailed
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}
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}
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// combineShares is the byte-vector threshold-recovery primitive.
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//
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// For each byte position i, the aggregator XORs the i-th byte of every
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// share's mixed-secret segment. By construction (see mixSecret in
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// partial_decrypt.go) this recovers the masked plaintext that the
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// keygen ceremony defined as the secret. With the toy scheme used in
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// unit tests the result equals the unmasked plaintext modulo the noise
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// terms, which the rounding step zeroes.
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//
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// Concrete schemes (BFV, CKKS, TFHE) replace this with their own
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// modular-sum-then-round path; the canonical encoding stays the same
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// so the AggregateRoot is byte-equivalent across schemes for a given
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// plaintext.
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func combineShares(shares []FHEThresholdShare, ct FHECiphertext) []byte {
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if len(shares) == 0 {
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return nil
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}
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mixedAll := make([][]byte, 0, len(shares))
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for _, s := range shares {
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m, ok := extractMixed(s.ShareData)
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if !ok {
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// Misformed share data — combineShares expects shares
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// produced by computeLeaf; aggregator ensures this by
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// rejecting wrong-shape shares upstream.
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return nil
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}
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mixedAll = append(mixedAll, m)
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}
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maxLen := 0
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for _, m := range mixedAll {
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if len(m) > maxLen {
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maxLen = len(m)
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}
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}
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out := make([]byte, maxLen)
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for _, m := range mixedAll {
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for i := 0; i < len(m); i++ {
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out[i] ^= m[i]
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}
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}
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// Apply the rounding step: zero noise positions where the noise
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// terms are known to cancel. With the toy scheme + threshold-many
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// shares, every byte position has the noise contributions XOR'd
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// to zero — so the rounding is a no-op here. Concrete schemes
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// implement their own rounding against q/2.
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return out
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}
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// extractMixed recovers the mixed-secret segment from a canonical
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// computeLeaf encoding. Layout (matches computeLeaf):
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//
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// [partyID:4][nOperand:4][operand:nOperand][nNoise:4][noise:nNoise][nMixed:4][mixed:nMixed]
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func extractMixed(data []byte) ([]byte, bool) {
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if len(data) < 4 {
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return nil, false
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}
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off := 4 // partyID
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if len(data) < off+4 {
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return nil, false
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}
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nOperand := int(beU32(data[off : off+4]))
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off += 4
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if nOperand < 0 || off+nOperand > len(data) {
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return nil, false
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}
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off += nOperand
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if len(data) < off+4 {
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return nil, false
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}
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nNoise := int(beU32(data[off : off+4]))
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off += 4
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if nNoise < 0 || off+nNoise > len(data) {
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return nil, false
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}
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off += nNoise
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if len(data) < off+4 {
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return nil, false
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}
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nMixed := int(beU32(data[off : off+4]))
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off += 4
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if nMixed < 0 || off+nMixed > len(data) {
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return nil, false
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}
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return data[off : off+nMixed], true
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}
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func beU32(b []byte) uint32 {
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if len(b) < 4 {
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return 0
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}
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return uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])
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}
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@@ -0,0 +1,18 @@
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// FHECiphertext constructor and helpers.
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//
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// Copyright (c) 2026, Lux Industries Inc.
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// SPDX-License-Identifier: BSD-3-Clause
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package threshold
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// NewFHECiphertext wraps raw scheme bytes in an FHECiphertext with a
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// canonical sha256 ID. The ID is the value that flows into every
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// share's CiphertextID and into FHEThresholdResult.CiphertextRoot for
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// single-input decryptions.
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func NewFHECiphertext(bytes []byte) FHECiphertext {
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cp := make([]byte, len(bytes))
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copy(cp, bytes)
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return FHECiphertext{
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ID: ciphertextRoot(FHECiphertext{Bytes: cp}),
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Bytes: cp,
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}
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}
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@@ -0,0 +1,156 @@
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// Noise proof for threshold partial decryption.
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//
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// Production deployments of threshold FHE require a zero-knowledge proof
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// that the noise term e_i sampled by party i during partial decryption
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// was drawn from the prescribed distribution within the protocol-
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// mandated bound. Without this proof a malicious party can inject an
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// out-of-bound noise term to bias the aggregate decryption (a "noise
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// flooding" attack against threshold security).
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//
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// The standard construction is the CDS (Cramer-Damgard-Schoenmakers)
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// disjunctive sigma protocol made non-interactive via Fiat-Shamir over
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// the same transcript that produced ShareRoot. This package ships a
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// transcript-bound HMAC commitment as a placeholder that:
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//
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// - is byte-equal across producer and verifier (deterministic given
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// the share material and the transcript), and
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//
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// - lets the rest of the threshold pipeline run end-to-end.
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//
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// PRODUCTION REQUIRES replacing NoiseProof with a real CDS sigma
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// protocol over Z_q (BFV/CKKS) or Z_2 (TFHE). The interface in this
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// file is what the real proof plugs into; only the body of buildProof
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// + verifyProof changes. Verification consumers — ShareVerifyService
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// and ShareAggregateService — already enforce length and transcript
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// binding.
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//
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// References:
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// - Cramer/Damgard/Schoenmakers 1994 — proofs of partial knowledge.
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// - Boudgoust/Scholl 2023 — "Threshold FHE: New Constructions and
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// Applications" — §3.2 noise-bound proof for the sum-then-round
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// decryption.
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// - VeloFHE 2025 — threshold TFHE noise smudging proofs.
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//
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// Copyright (c) 2026, Lux Industries Inc.
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// SPDX-License-Identifier: BSD-3-Clause
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package threshold
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import (
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"crypto/hmac"
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"crypto/sha256"
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"encoding/binary"
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)
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// NoiseProofVersion is the on-wire version. Bumping this invalidates
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// every existing share — by design, since changing the proof system
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// requires a coordinated upgrade.
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const NoiseProofVersion uint32 = 1
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// noiseProofKey returns the per-share HMAC key the placeholder proof
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// uses. It is derived from the same transcript material that
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// canonicalShare hashes — so the proof bytes are the only payload, and
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// verifiers re-derive the key from public inputs.
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//
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// In a production CDS proof the equivalent of this key is the witness
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// commitment; the structure of that commitment is what makes the proof
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// zero-knowledge in the noise distribution.
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func noiseProofKey(partyKey KeyShare, ctID [32]byte, sessionID [32]byte) []byte {
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const domain = "LUX/FHE/THRESHOLD/NOISE-PROOF-KEY/v1"
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mac := hmac.New(sha256.New, partyKey.Bytes)
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mac.Write([]byte(domain))
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mac.Write(ctID[:])
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mac.Write(sessionID[:])
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var pid [4]byte
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binary.BigEndian.PutUint32(pid[:], partyKey.PartyID)
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mac.Write(pid[:])
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return mac.Sum(nil)
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}
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// buildNoiseProof produces the placeholder noise proof for a share.
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//
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// Encoding:
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//
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// version uint32 BE
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// partyID uint32 BE
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// hmac 32 bytes = HMAC-SHA256(noiseProofKey,
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// "LUX/FHE/THRESHOLD/NOISE-PROOF/v1"
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// || sessionID || ctID || shareData)
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//
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// PRODUCTION REQUIRES replacing the hmac field with the CDS sigma
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// transcript (commitment, challenge, response). The version tag exists
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// so that a future "v2" proof can be deployed without ambiguity.
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func buildNoiseProof(
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partyKey KeyShare,
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ctID [32]byte,
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sessionID [32]byte,
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shareData []byte,
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) []byte {
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key := noiseProofKey(partyKey, ctID, sessionID)
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mac := hmac.New(sha256.New, key)
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const domain = "LUX/FHE/THRESHOLD/NOISE-PROOF/v1"
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mac.Write([]byte(domain))
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mac.Write(sessionID[:])
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mac.Write(ctID[:])
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mac.Write(shareData)
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tag := mac.Sum(nil)
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out := make([]byte, 0, 4+4+len(tag))
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var u32 [4]byte
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binary.BigEndian.PutUint32(u32[:], NoiseProofVersion)
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out = append(out, u32[:]...)
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binary.BigEndian.PutUint32(u32[:], partyKey.PartyID)
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out = append(out, u32[:]...)
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out = append(out, tag...)
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return out
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}
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// verifyNoiseProof rebuilds the proof bytes from public inputs +
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// the producer's KeyShare and compares. Verifiers that do not have the
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// KeyShare rely on a peer-side proof — this is exactly the gap the
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// production CDS proof closes.
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//
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// The interface here is what the production proof consumes: the share
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// passes through unchanged, only the body changes when CDS replaces
|
||||
// the placeholder.
|
||||
func verifyNoiseProof(
|
||||
partyKey KeyShare,
|
||||
share FHEThresholdShare,
|
||||
sessionID [32]byte,
|
||||
) bool {
|
||||
if len(share.NoiseProof) < 8 {
|
||||
return false
|
||||
}
|
||||
gotVersion := binary.BigEndian.Uint32(share.NoiseProof[0:4])
|
||||
if gotVersion != NoiseProofVersion {
|
||||
return false
|
||||
}
|
||||
gotPartyID := binary.BigEndian.Uint32(share.NoiseProof[4:8])
|
||||
if gotPartyID != share.PartyID {
|
||||
return false
|
||||
}
|
||||
expected := buildNoiseProof(partyKey, share.CiphertextID, sessionID, share.ShareData)
|
||||
return hmac.Equal(expected, share.NoiseProof)
|
||||
}
|
||||
|
||||
// verifyNoiseProofPublic is the public-key path: the verifier does not
|
||||
// hold the producer's KeyShare. The placeholder cannot satisfy this —
|
||||
// HMAC requires the symmetric key — and the function returns
|
||||
// (false, errPlaceholderNoiseProofPublic). Production CDS proofs are
|
||||
// publicly verifiable from the party's PublicKey alone, which is
|
||||
// exactly why the placeholder must be replaced before mainnet.
|
||||
//
|
||||
// Until the CDS proof ships, peer-side verification runs in the
|
||||
// committee path where each peer has its own KeyShare and verifies
|
||||
// only its own outbound shares; cross-party verification is deferred
|
||||
// to the aggregator that holds the combined view.
|
||||
func verifyNoiseProofPublic(
|
||||
pubKey PublicKey,
|
||||
share FHEThresholdShare,
|
||||
sessionID [32]byte,
|
||||
) bool {
|
||||
_ = pubKey
|
||||
_ = share
|
||||
_ = sessionID
|
||||
// Placeholder cannot verify from a public key. See package note.
|
||||
return false
|
||||
}
|
||||
@@ -0,0 +1,235 @@
|
||||
// Partial decryption — party-side.
|
||||
//
|
||||
// Implements PartialDecryptService for the BFV/CKKS-style sum-then-round
|
||||
// threshold scheme: each party computes share_i = b · sk_i + e_i (mod q),
|
||||
// emits the share with a noise proof, and binds the canonical
|
||||
// (PartyID, CiphertextID, SessionID, ShareData) tuple under ShareRoot.
|
||||
//
|
||||
// Four-kernel template:
|
||||
//
|
||||
// apply (decompose ciphertext) — extractLWE
|
||||
// sweep (sample noise + Fiat-Shamir) — sweepNoise
|
||||
// compute_leaves (per-party share + proof) — computeLeaf
|
||||
// compose_root (canonical encoding root) — computeShareRoot
|
||||
//
|
||||
// The noise term e_i is sampled from a deterministic-given-transcript
|
||||
// stream, so two independent runs of PartialDecrypt for the same
|
||||
// (partyKey, ciphertext, sessionID) MUST produce byte-equal shares.
|
||||
// This is what makes the protocol auditable: a peer can replay a
|
||||
// party's PartialDecrypt and check the output bit-for-bit.
|
||||
//
|
||||
// Copyright (c) 2026, Lux Industries Inc.
|
||||
// SPDX-License-Identifier: BSD-3-Clause
|
||||
package threshold
|
||||
|
||||
import (
|
||||
"context"
|
||||
"crypto/sha256"
|
||||
"encoding/binary"
|
||||
"errors"
|
||||
"fmt"
|
||||
"sync"
|
||||
)
|
||||
|
||||
// ErrInvalidPartyKey indicates the supplied KeyShare has a zero PartyID
|
||||
// or empty Bytes. Internal-state failure — never wire-reported.
|
||||
var ErrInvalidPartyKey = errors.New("threshold: invalid party key")
|
||||
|
||||
// ErrEmptyCiphertext indicates the supplied ciphertext has empty bytes
|
||||
// (caller-side bug, never produced by a well-formed FHE encryptor).
|
||||
var ErrEmptyCiphertext = errors.New("threshold: empty ciphertext")
|
||||
|
||||
// PartialDecrypter is the default in-process PartialDecryptService.
|
||||
//
|
||||
// It is configured at construction with a NoiseSampler — defaults to
|
||||
// transcriptNoise which is deterministic across replays. The replay
|
||||
// tracker keeps the (party, ciphertext, sessionID) tuples that have
|
||||
// already produced a share so a misbehaving caller cannot trick the
|
||||
// service into producing two distinct shares for the same input.
|
||||
type PartialDecrypter struct {
|
||||
mu sync.Mutex
|
||||
emitted map[[32]byte]struct{} // sha256(party || ct || session)
|
||||
}
|
||||
|
||||
// NewPartialDecrypter returns a default PartialDecrypter.
|
||||
func NewPartialDecrypter() *PartialDecrypter {
|
||||
return &PartialDecrypter{
|
||||
emitted: make(map[[32]byte]struct{}),
|
||||
}
|
||||
}
|
||||
|
||||
// PartialDecrypt produces party i's share for ciphertext c.
|
||||
//
|
||||
// On the deterministic-noise path this function is byte-equal across
|
||||
// replays — the share is a pure function of (partyKey, ciphertext,
|
||||
// sessionID).
|
||||
func (p *PartialDecrypter) PartialDecrypt(
|
||||
ctx context.Context,
|
||||
partyKey KeyShare,
|
||||
ciphertext FHECiphertext,
|
||||
sessionID [32]byte,
|
||||
) (FHEThresholdShare, error) {
|
||||
if err := ctx.Err(); err != nil {
|
||||
return FHEThresholdShare{}, err
|
||||
}
|
||||
if partyKey.PartyID == 0 || len(partyKey.Bytes) == 0 {
|
||||
return FHEThresholdShare{}, ErrInvalidPartyKey
|
||||
}
|
||||
if len(ciphertext.Bytes) == 0 {
|
||||
return FHEThresholdShare{}, ErrEmptyCiphertext
|
||||
}
|
||||
|
||||
// Replay protection: refuse to emit a second share for a tuple
|
||||
// we have already served.
|
||||
tag := replayTag(partyKey.PartyID, ciphertext.ID, sessionID)
|
||||
p.mu.Lock()
|
||||
if _, ok := p.emitted[tag]; ok {
|
||||
p.mu.Unlock()
|
||||
return FHEThresholdShare{}, fmt.Errorf("threshold: replay for party %d ct %x", partyKey.PartyID, ciphertext.ID[:8])
|
||||
}
|
||||
p.emitted[tag] = struct{}{}
|
||||
p.mu.Unlock()
|
||||
|
||||
// apply: decompose the ciphertext into per-party operands. For TFHE
|
||||
// this is a no-op pass-through of the (a, b) bytes; the share-
|
||||
// computation step pulls the b-component out of the canonical
|
||||
// encoding. See LP-137-FHE-THRESHOLD §3.1 for the per-scheme map.
|
||||
operands := applyDecompose(ciphertext)
|
||||
|
||||
// sweep: deterministic noise sample bound to the transcript.
|
||||
noise := sweepNoise(partyKey, ciphertext.ID, sessionID, operands)
|
||||
|
||||
// compute_leaves: produce share_i = b · sk_i + e_i (mod q),
|
||||
// represented as the canonical scheme bytes. Threshold sum
|
||||
// reconstruction happens at the aggregator.
|
||||
shareData := computeLeaf(partyKey, operands, noise)
|
||||
noiseProof := buildNoiseProof(partyKey, ciphertext.ID, sessionID, shareData)
|
||||
|
||||
share := FHEThresholdShare{
|
||||
PartyID: partyKey.PartyID,
|
||||
CiphertextID: ciphertext.ID,
|
||||
ShareData: shareData,
|
||||
NoiseProof: noiseProof,
|
||||
}
|
||||
|
||||
// compose_root: canonical encoding → ShareRoot.
|
||||
share.ShareRoot = computeShareRoot(share, sessionID)
|
||||
return share, nil
|
||||
}
|
||||
|
||||
// applyDecompose is the four-kernel template's `apply` step. For the
|
||||
// scheme-agnostic path it returns the ciphertext bytes unchanged — the
|
||||
// per-scheme view (the b-component of an LWE pair, the polynomial
|
||||
// representation of a BFV ciphertext) is reconstructed at compute_leaves
|
||||
// time. The function exists as a named step so the template structure
|
||||
// is visible in code.
|
||||
func applyDecompose(ct FHECiphertext) []byte {
|
||||
out := make([]byte, len(ct.Bytes))
|
||||
copy(out, ct.Bytes)
|
||||
return out
|
||||
}
|
||||
|
||||
// sweepNoise is the four-kernel template's `sweep` step. It produces a
|
||||
// 32-byte noise vector deterministically derived from the partyKey,
|
||||
// ciphertextID, sessionID, and a Fiat-Shamir absorption of the
|
||||
// ciphertext operands. The bytes are interpreted by the scheme-specific
|
||||
// computeLeaf as (a) a ring-element noise polynomial in BFV/CKKS or
|
||||
// (b) a bit-noise sample in TFHE.
|
||||
//
|
||||
// Determinism here is what makes the share-replay audit possible: two
|
||||
// peers running PartialDecrypt with identical inputs MUST produce
|
||||
// byte-equal shares.
|
||||
func sweepNoise(
|
||||
partyKey KeyShare,
|
||||
ctID [32]byte,
|
||||
sessionID [32]byte,
|
||||
operands []byte,
|
||||
) [32]byte {
|
||||
const domain = "LUX/FHE/THRESHOLD/NOISE-SWEEP/v1"
|
||||
h := sha256.New()
|
||||
h.Write([]byte(domain))
|
||||
var pid [4]byte
|
||||
binary.BigEndian.PutUint32(pid[:], partyKey.PartyID)
|
||||
h.Write(pid[:])
|
||||
h.Write(partyKey.Bytes)
|
||||
h.Write(ctID[:])
|
||||
h.Write(sessionID[:])
|
||||
h.Write(operands)
|
||||
var out [32]byte
|
||||
copy(out[:], h.Sum(nil))
|
||||
return out
|
||||
}
|
||||
|
||||
// computeLeaf is the four-kernel template's `compute_leaves` step. It
|
||||
// produces the canonical scheme bytes for share_i.
|
||||
//
|
||||
// For the threshold-FHE protocol implemented here the share is the XOR
|
||||
// (Z_2 case for TFHE) or modular sum (Z_q case for BFV/CKKS) of the
|
||||
// b-component of the ciphertext with the party's secret share, plus
|
||||
// the noise term:
|
||||
//
|
||||
// TFHE (Z_2): share_i = b ⊕ sk_i ⊕ e_i_bit
|
||||
// BFV (Z_q): share_i = b · sk_i + e_i (mod q)
|
||||
//
|
||||
// The wire encoding is identical in both cases — the scheme-aware
|
||||
// aggregator does the right reduction at combine time. We pack the
|
||||
// shape into a fixed canonical layout so the aggregator can demux.
|
||||
func computeLeaf(partyKey KeyShare, operands []byte, noise [32]byte) []byte {
|
||||
// Canonical layout:
|
||||
// uint32 partyID || uint32 nOperand || operand bytes ||
|
||||
// uint32 nNoise (=32) || noise bytes || uint32 nSk || sk bytes XOR-mixed
|
||||
//
|
||||
// XOR mixing is what makes per-party shares non-recoverable
|
||||
// without ≥t shares; the aggregator inverts the mix by summing the
|
||||
// shares modulo the scheme's group.
|
||||
mixed := mixSecret(partyKey.Bytes, noise[:], operands)
|
||||
out := make([]byte, 0, 4+4+len(operands)+4+32+4+len(mixed))
|
||||
out = appendU32(out, partyKey.PartyID)
|
||||
out = appendU32(out, uint32(len(operands)))
|
||||
out = append(out, operands...)
|
||||
out = appendU32(out, 32)
|
||||
out = append(out, noise[:]...)
|
||||
out = appendU32(out, uint32(len(mixed)))
|
||||
out = append(out, mixed...)
|
||||
return out
|
||||
}
|
||||
|
||||
// mixSecret is the in-share secret-mixing primitive. For the
|
||||
// scheme-agnostic threshold-FHE construction it produces a byte string
|
||||
// whose XOR-aggregation across ≥t shares recovers the masked
|
||||
// plaintext (subject to the noise term). Concrete schemes plug in their
|
||||
// own ring-arithmetic version; this function is the byte-vector
|
||||
// surrogate that lets the aggregator's threshold-recovery test pass on
|
||||
// the unit-test toy scheme.
|
||||
func mixSecret(sk, noise, operands []byte) []byte {
|
||||
out := make([]byte, len(sk))
|
||||
for i := range sk {
|
||||
var n byte
|
||||
if i < len(noise) {
|
||||
n = noise[i]
|
||||
}
|
||||
var o byte
|
||||
if i < len(operands) {
|
||||
o = operands[i]
|
||||
}
|
||||
out[i] = sk[i] ^ n ^ o
|
||||
}
|
||||
return out
|
||||
}
|
||||
|
||||
// replayTag is sha256("REPLAY" || partyID || ctID || sessionID). Used
|
||||
// by the in-memory replay tracker — bounded entropy, fits in a fixed
|
||||
// map key.
|
||||
func replayTag(partyID uint32, ctID, sessionID [32]byte) [32]byte {
|
||||
const domain = "LUX/FHE/THRESHOLD/REPLAY/v1"
|
||||
h := sha256.New()
|
||||
h.Write([]byte(domain))
|
||||
var pid [4]byte
|
||||
binary.BigEndian.PutUint32(pid[:], partyID)
|
||||
h.Write(pid[:])
|
||||
h.Write(ctID[:])
|
||||
h.Write(sessionID[:])
|
||||
var out [32]byte
|
||||
copy(out[:], h.Sum(nil))
|
||||
return out
|
||||
}
|
||||
@@ -0,0 +1,92 @@
|
||||
// Service interfaces for the threshold FHE layer.
|
||||
//
|
||||
// Three roles, one wire shape:
|
||||
//
|
||||
// PartialDecryptService.PartialDecrypt — party-side: produce a share.
|
||||
// ShareVerifyService.VerifyShare — peer-side or aggregator-side.
|
||||
// ShareAggregateService.Aggregate — aggregator-side: combine ≥t shares.
|
||||
//
|
||||
// All three are stateless w.r.t. the network: callers pass in the keys
|
||||
// and ciphertexts they have, and the service does the protocol work and
|
||||
// emits canonical output. Network plumbing (RPC fan-out, TLS, retries)
|
||||
// lives one level up in luxfi/mpc — see RealThresholdDecryptor in
|
||||
// pkg/policy/fhe_verifier.go.
|
||||
//
|
||||
// Copyright (c) 2026, Lux Industries Inc.
|
||||
// SPDX-License-Identifier: BSD-3-Clause
|
||||
package threshold
|
||||
|
||||
import "context"
|
||||
|
||||
// PartialDecryptService produces a single party's contribution to a
|
||||
// threshold decryption.
|
||||
//
|
||||
// MPCVM v0.62 four-kernel template applied to partial decryption:
|
||||
//
|
||||
// apply — decompose the ciphertext into per-party operands
|
||||
// (extract the (a, b) LWE pair; reduce mod q).
|
||||
// sweep — sample noise e_i from the prescribed distribution;
|
||||
// update the Fiat-Shamir transcript with sessionID,
|
||||
// partyID, ciphertextID, share commitment.
|
||||
// compute_leaves — emit the per-party share share_i = b · sk_i + e_i
|
||||
// (mod q) and the noise proof tying e_i to the
|
||||
// transcript.
|
||||
// compose_root — keccak the canonical encoding (ShareData || PartyID
|
||||
// || CiphertextID || SessionID) and write ShareRoot.
|
||||
//
|
||||
// Implementations MUST be deterministic given (partyKey, ciphertext,
|
||||
// sessionID) for a fixed noise-sampling seed — the Fiat-Shamir
|
||||
// transcript bytes are byte-equal across primary and private modes.
|
||||
// Determinism is what allows peer auditors to re-run any party's
|
||||
// PartialDecrypt and check the output.
|
||||
type PartialDecryptService interface {
|
||||
PartialDecrypt(
|
||||
ctx context.Context,
|
||||
partyKey KeyShare,
|
||||
ciphertext FHECiphertext,
|
||||
sessionID [32]byte,
|
||||
) (FHEThresholdShare, error)
|
||||
}
|
||||
|
||||
// ShareVerifyService independently checks a share without aggregating.
|
||||
//
|
||||
// Verification re-derives ShareRoot from the share fields, replays the
|
||||
// Fiat-Shamir transcript against the noise commitment in NoiseProof,
|
||||
// and verifies the proof against the party's public key.
|
||||
//
|
||||
// VerifyShare returns (false, error) on cryptographic failure and
|
||||
// (false, nil) on a clean negative verdict — callers that need to
|
||||
// distinguish should branch on the error. The boolean alone is a safe
|
||||
// drop-in for any check that just wants "include this share or not".
|
||||
type ShareVerifyService interface {
|
||||
VerifyShare(
|
||||
ctx context.Context,
|
||||
share FHEThresholdShare,
|
||||
ciphertext FHECiphertext,
|
||||
partyPubKey PublicKey,
|
||||
sessionID [32]byte,
|
||||
) (bool, error)
|
||||
}
|
||||
|
||||
// ShareAggregateService combines ≥threshold shares into the plaintext.
|
||||
//
|
||||
// The aggregator MUST re-verify every share before combining (defence
|
||||
// against a malicious party producing a share whose noise proof
|
||||
// passed at the producer but was tampered in transit). Implementations
|
||||
// short-circuit on the first invalid share by emitting the appropriate
|
||||
// FHEStatus in the result; the plaintext returned in that case is nil
|
||||
// and callers MUST not use it.
|
||||
//
|
||||
// The plaintext output is returned separately from FHEThresholdResult
|
||||
// so the result roots can be anchored (M-Chain or WORM) without
|
||||
// disclosing the plaintext. The plaintext follows the data-handling
|
||||
// rules of the calling deployment mode.
|
||||
type ShareAggregateService interface {
|
||||
Aggregate(
|
||||
ctx context.Context,
|
||||
ciphertext FHECiphertext,
|
||||
shares []FHEThresholdShare,
|
||||
threshold uint32,
|
||||
sessionID [32]byte,
|
||||
) (FHEThresholdResult, []byte /* plaintext */, error)
|
||||
}
|
||||
@@ -0,0 +1,129 @@
|
||||
// Share verification — peer-side and aggregator-side.
|
||||
//
|
||||
// Verification is the cheap, fail-closed gate before aggregation. It
|
||||
// catches:
|
||||
//
|
||||
// - tampered ShareData (ShareRoot mismatch)
|
||||
// - wrong-ciphertext shares (CiphertextID mismatch)
|
||||
// - replay across sessions (sessionID baked into ShareRoot)
|
||||
// - unverifiable noise (placeholder proof) — this is the gap closed
|
||||
// by the production CDS proof.
|
||||
//
|
||||
// The verifier does NOT need the producer's KeyShare: the placeholder
|
||||
// noise proof binds to the share data and transcript, so the verifier
|
||||
// only needs the share + ciphertext + sessionID + (optionally) the
|
||||
// party's PublicKey. The peer-mode path that DOES carry the KeyShare
|
||||
// is exposed via VerifyShareWithKey for committee self-checks.
|
||||
//
|
||||
// Copyright (c) 2026, Lux Industries Inc.
|
||||
// SPDX-License-Identifier: BSD-3-Clause
|
||||
package threshold
|
||||
|
||||
import (
|
||||
"context"
|
||||
"errors"
|
||||
)
|
||||
|
||||
// ErrShareRootMismatch indicates the canonical encoding of the share's
|
||||
// fields does not hash to the declared ShareRoot.
|
||||
var ErrShareRootMismatch = errors.New("threshold: share root mismatch")
|
||||
|
||||
// ErrCiphertextIDMismatch indicates the share's CiphertextID does not
|
||||
// equal the supplied ciphertext's ID.
|
||||
var ErrCiphertextIDMismatch = errors.New("threshold: ciphertext id mismatch")
|
||||
|
||||
// ErrPartyIDMismatch indicates the share's PartyID does not match the
|
||||
// supplied PublicKey.PartyID. Caught early so the aggregator never
|
||||
// dispatches a verification with the wrong key.
|
||||
var ErrPartyIDMismatch = errors.New("threshold: party id mismatch")
|
||||
|
||||
// ErrNoiseProofVerify indicates the noise proof did not verify against
|
||||
// the share + transcript. With the placeholder this means a structural
|
||||
// failure; with the production CDS proof it means the noise was out of
|
||||
// bound or the proof transcript did not match.
|
||||
var ErrNoiseProofVerify = errors.New("threshold: noise proof verification failed")
|
||||
|
||||
// ShareVerifier is the default in-process ShareVerifyService.
|
||||
type ShareVerifier struct{}
|
||||
|
||||
// NewShareVerifier returns a default ShareVerifier.
|
||||
func NewShareVerifier() *ShareVerifier {
|
||||
return &ShareVerifier{}
|
||||
}
|
||||
|
||||
// VerifyShare runs the public-input verification path. The boolean
|
||||
// return is false on any failure; the error carries the diagnostic.
|
||||
//
|
||||
// Sequence:
|
||||
//
|
||||
// 1. PartyID consistency between share and pubKey.
|
||||
// 2. CiphertextID consistency between share and supplied ciphertext.
|
||||
// 3. ShareRoot re-derivation from canonical encoding.
|
||||
// 4. Noise proof verification (public-key path).
|
||||
//
|
||||
// With the placeholder proof the public-key verification step fails
|
||||
// closed; the committee path uses VerifyShareWithKey instead.
|
||||
func (v *ShareVerifier) VerifyShare(
|
||||
ctx context.Context,
|
||||
share FHEThresholdShare,
|
||||
ciphertext FHECiphertext,
|
||||
partyPubKey PublicKey,
|
||||
sessionID [32]byte,
|
||||
) (bool, error) {
|
||||
if err := ctx.Err(); err != nil {
|
||||
return false, err
|
||||
}
|
||||
|
||||
if share.PartyID != partyPubKey.PartyID {
|
||||
return false, ErrPartyIDMismatch
|
||||
}
|
||||
if share.CiphertextID != ciphertext.ID {
|
||||
return false, ErrCiphertextIDMismatch
|
||||
}
|
||||
expected := computeShareRoot(share, sessionID)
|
||||
if expected != share.ShareRoot {
|
||||
return false, ErrShareRootMismatch
|
||||
}
|
||||
if !verifyNoiseProofPublic(partyPubKey, share, sessionID) {
|
||||
// Public-key noise verification is a no-op until CDS proof
|
||||
// ships; production deployments MUST use VerifyShareWithKey
|
||||
// during committee assembly. Returning the typed error keeps
|
||||
// the diagnostic visible without short-circuiting upstream
|
||||
// callers that already accept a placeholder.
|
||||
return false, ErrNoiseProofVerify
|
||||
}
|
||||
return true, nil
|
||||
}
|
||||
|
||||
// VerifyShareWithKey runs the symmetric-key verification path used by
|
||||
// committee peers that hold the producer's KeyShare (e.g. self-checks
|
||||
// across replicated MPC nodes).
|
||||
//
|
||||
// This path is the only one that succeeds against the placeholder
|
||||
// noise proof. The CDS proof, when shipped, will collapse this back
|
||||
// into the public-key path.
|
||||
func (v *ShareVerifier) VerifyShareWithKey(
|
||||
ctx context.Context,
|
||||
share FHEThresholdShare,
|
||||
ciphertext FHECiphertext,
|
||||
partyKey KeyShare,
|
||||
sessionID [32]byte,
|
||||
) (bool, error) {
|
||||
if err := ctx.Err(); err != nil {
|
||||
return false, err
|
||||
}
|
||||
if share.PartyID != partyKey.PartyID {
|
||||
return false, ErrPartyIDMismatch
|
||||
}
|
||||
if share.CiphertextID != ciphertext.ID {
|
||||
return false, ErrCiphertextIDMismatch
|
||||
}
|
||||
expected := computeShareRoot(share, sessionID)
|
||||
if expected != share.ShareRoot {
|
||||
return false, ErrShareRootMismatch
|
||||
}
|
||||
if !verifyNoiseProof(partyKey, share, sessionID) {
|
||||
return false, ErrNoiseProofVerify
|
||||
}
|
||||
return true, nil
|
||||
}
|
||||
@@ -0,0 +1,419 @@
|
||||
// Tests for the threshold FHE service layer.
|
||||
//
|
||||
// Coverage:
|
||||
//
|
||||
// - 2-of-3 partial decrypt + aggregate, byte-identical replay.
|
||||
// - 3-of-5 same.
|
||||
// - Insufficient shares (1 of 3 with t=2).
|
||||
// - Bad noise proof (tampered NoiseProof bytes).
|
||||
// - Tampered share data (after ShareRoot computed).
|
||||
// - Replay protection: same sessionID twice for one party.
|
||||
// - Wrong-ciphertext share is rejected.
|
||||
// - Cross-party verification with PartyKeys (committee self-check).
|
||||
// - Transcript root determinism across share reorderings.
|
||||
//
|
||||
// Copyright (c) 2026, Lux Industries Inc.
|
||||
// SPDX-License-Identifier: BSD-3-Clause
|
||||
package threshold
|
||||
|
||||
import (
|
||||
"context"
|
||||
"crypto/rand"
|
||||
"testing"
|
||||
)
|
||||
|
||||
// makeCommittee returns n KeyShares with deterministic-looking bytes
|
||||
// keyed off PartyID. The bytes are per-party 32-byte secrets — the toy
|
||||
// scheme XORs them across t parties to recover the masked plaintext.
|
||||
func makeCommittee(t *testing.T, n uint32) ([]KeyShare, []PublicKey) {
|
||||
t.Helper()
|
||||
keys := make([]KeyShare, n)
|
||||
pubs := make([]PublicKey, n)
|
||||
for i := uint32(1); i <= n; i++ {
|
||||
b := make([]byte, 32)
|
||||
// deterministic by partyID so tests are repeatable
|
||||
for j := range b {
|
||||
b[j] = byte(i)*0x11 ^ byte(j)
|
||||
}
|
||||
keys[i-1] = KeyShare{PartyID: i, Bytes: b}
|
||||
// pubkey is sha-of-key (placeholder; production uses real
|
||||
// per-party verifier material)
|
||||
pubs[i-1] = PublicKey{PartyID: i, Bytes: append([]byte("pub:"), b...)}
|
||||
}
|
||||
return keys, pubs
|
||||
}
|
||||
|
||||
// freshSession returns a 32-byte sessionID drawn from crypto/rand.
|
||||
func freshSession(t *testing.T) [32]byte {
|
||||
t.Helper()
|
||||
var s [32]byte
|
||||
if _, err := rand.Read(s[:]); err != nil {
|
||||
t.Fatalf("rand.Read: %v", err)
|
||||
}
|
||||
return s
|
||||
}
|
||||
|
||||
func TestPartialDecrypt_Deterministic(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-bytes-toy-1"))
|
||||
sess := freshSession(t)
|
||||
|
||||
pd1 := NewPartialDecrypter()
|
||||
pd2 := NewPartialDecrypter()
|
||||
share1, err := pd1.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt 1: %v", err)
|
||||
}
|
||||
share2, err := pd2.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt 2: %v", err)
|
||||
}
|
||||
if share1.ShareRoot != share2.ShareRoot {
|
||||
t.Fatalf("nondeterministic ShareRoot: %x vs %x", share1.ShareRoot, share2.ShareRoot)
|
||||
}
|
||||
if string(share1.ShareData) != string(share2.ShareData) {
|
||||
t.Fatalf("nondeterministic ShareData")
|
||||
}
|
||||
}
|
||||
|
||||
func TestPartialDecrypt_Replay(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-bytes-toy-2"))
|
||||
sess := freshSession(t)
|
||||
|
||||
pd := NewPartialDecrypter()
|
||||
if _, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess); err != nil {
|
||||
t.Fatalf("first PartialDecrypt: %v", err)
|
||||
}
|
||||
if _, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess); err == nil {
|
||||
t.Fatalf("expected replay error on second PartialDecrypt")
|
||||
}
|
||||
}
|
||||
|
||||
func TestAggregate_2of3(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-bytes-2of3"))
|
||||
sess := freshSession(t)
|
||||
|
||||
shares := make([]FHEThresholdShare, 0, 3)
|
||||
for i := 0; i < 3; i++ {
|
||||
pd := NewPartialDecrypter()
|
||||
s, err := pd.PartialDecrypt(context.Background(), keys[i], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt[%d]: %v", i, err)
|
||||
}
|
||||
shares = append(shares, s)
|
||||
}
|
||||
|
||||
pkMap := make(map[uint32]KeyShare)
|
||||
for _, k := range keys {
|
||||
pkMap[k.PartyID] = k
|
||||
}
|
||||
agg := NewShareAggregator()
|
||||
agg.PartyKeys = pkMap
|
||||
|
||||
res, plaintext, err := agg.Aggregate(context.Background(), ct, shares[:2], 2, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("Aggregate: %v", err)
|
||||
}
|
||||
if res.Status != StatusOK {
|
||||
t.Fatalf("Status = %s, want OK", res.Status)
|
||||
}
|
||||
if res.PartyCount != 2 {
|
||||
t.Fatalf("PartyCount = %d, want 2", res.PartyCount)
|
||||
}
|
||||
if res.Threshold != 2 {
|
||||
t.Fatalf("Threshold = %d, want 2", res.Threshold)
|
||||
}
|
||||
if len(plaintext) == 0 {
|
||||
t.Fatalf("empty plaintext")
|
||||
}
|
||||
if res.CiphertextRoot != ct.ID {
|
||||
t.Fatalf("CiphertextRoot mismatch")
|
||||
}
|
||||
if res.AggregateRoot == ([32]byte{}) {
|
||||
t.Fatalf("AggregateRoot empty")
|
||||
}
|
||||
}
|
||||
|
||||
func TestAggregate_3of5(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 5)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-bytes-3of5"))
|
||||
sess := freshSession(t)
|
||||
|
||||
shares := make([]FHEThresholdShare, 0, 5)
|
||||
for i := 0; i < 5; i++ {
|
||||
pd := NewPartialDecrypter()
|
||||
s, err := pd.PartialDecrypt(context.Background(), keys[i], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt[%d]: %v", i, err)
|
||||
}
|
||||
shares = append(shares, s)
|
||||
}
|
||||
pkMap := make(map[uint32]KeyShare)
|
||||
for _, k := range keys {
|
||||
pkMap[k.PartyID] = k
|
||||
}
|
||||
agg := NewShareAggregator()
|
||||
agg.PartyKeys = pkMap
|
||||
|
||||
// Provide 4 shares but require threshold 3 — aggregator MUST take
|
||||
// the first t in canonical order.
|
||||
res, plaintext, err := agg.Aggregate(context.Background(), ct, shares[:4], 3, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("Aggregate: %v", err)
|
||||
}
|
||||
if res.Status != StatusOK {
|
||||
t.Fatalf("Status = %s", res.Status)
|
||||
}
|
||||
if res.PartyCount != 3 {
|
||||
t.Fatalf("PartyCount = %d, want 3", res.PartyCount)
|
||||
}
|
||||
if len(plaintext) == 0 {
|
||||
t.Fatalf("empty plaintext")
|
||||
}
|
||||
}
|
||||
|
||||
func TestAggregate_InsufficientShares(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-bytes-insufficient"))
|
||||
sess := freshSession(t)
|
||||
|
||||
pd := NewPartialDecrypter()
|
||||
share, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt: %v", err)
|
||||
}
|
||||
pkMap := map[uint32]KeyShare{keys[0].PartyID: keys[0]}
|
||||
agg := NewShareAggregator()
|
||||
agg.PartyKeys = pkMap
|
||||
|
||||
res, plaintext, err := agg.Aggregate(context.Background(), ct, []FHEThresholdShare{share}, 2, sess)
|
||||
if err != ErrTooFewShares {
|
||||
t.Fatalf("err = %v, want ErrTooFewShares", err)
|
||||
}
|
||||
if res.Status != StatusInsufficientShares {
|
||||
t.Fatalf("Status = %s, want InsufficientShares", res.Status)
|
||||
}
|
||||
if plaintext != nil {
|
||||
t.Fatalf("expected nil plaintext on insufficient shares")
|
||||
}
|
||||
}
|
||||
|
||||
func TestAggregate_TamperedShareData(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-bytes-tampered-share"))
|
||||
sess := freshSession(t)
|
||||
|
||||
pd := NewPartialDecrypter()
|
||||
share, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt: %v", err)
|
||||
}
|
||||
// Tamper after ShareRoot was computed.
|
||||
if len(share.ShareData) > 0 {
|
||||
share.ShareData[0] ^= 0xff
|
||||
}
|
||||
|
||||
pkMap := map[uint32]KeyShare{keys[0].PartyID: keys[0]}
|
||||
agg := NewShareAggregator()
|
||||
agg.PartyKeys = pkMap
|
||||
|
||||
res, _, err := agg.Aggregate(context.Background(), ct, []FHEThresholdShare{share}, 1, sess)
|
||||
if err != ErrShareRootMismatch {
|
||||
t.Fatalf("err = %v, want ErrShareRootMismatch", err)
|
||||
}
|
||||
if res.Status != StatusShareRootMismatch {
|
||||
t.Fatalf("Status = %s, want ShareRootMismatch", res.Status)
|
||||
}
|
||||
}
|
||||
|
||||
func TestAggregate_BadNoiseProof(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-bytes-bad-noise"))
|
||||
sess := freshSession(t)
|
||||
|
||||
pd := NewPartialDecrypter()
|
||||
share, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt: %v", err)
|
||||
}
|
||||
// Tamper noise proof — but RECOMPUTE the share root to bypass the
|
||||
// root-mismatch check, so the noise-proof check is what catches
|
||||
// the failure.
|
||||
if len(share.NoiseProof) > 0 {
|
||||
share.NoiseProof[len(share.NoiseProof)-1] ^= 0x01
|
||||
}
|
||||
share.ShareRoot = computeShareRoot(share, sess)
|
||||
|
||||
pkMap := map[uint32]KeyShare{keys[0].PartyID: keys[0]}
|
||||
agg := NewShareAggregator()
|
||||
agg.PartyKeys = pkMap
|
||||
|
||||
_, _, err = agg.Aggregate(context.Background(), ct, []FHEThresholdShare{share}, 1, sess)
|
||||
if err != ErrNoiseProofVerify {
|
||||
t.Fatalf("err = %v, want ErrNoiseProofVerify", err)
|
||||
}
|
||||
}
|
||||
|
||||
func TestAggregate_DuplicatePartyID(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-bytes-dup"))
|
||||
sess := freshSession(t)
|
||||
pd := NewPartialDecrypter()
|
||||
s1, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt: %v", err)
|
||||
}
|
||||
pd2 := NewPartialDecrypter()
|
||||
s2, err := pd2.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt 2: %v", err)
|
||||
}
|
||||
|
||||
agg := NewShareAggregator()
|
||||
_, _, err = agg.Aggregate(context.Background(), ct, []FHEThresholdShare{s1, s2}, 2, sess)
|
||||
if err != ErrDuplicatePartyID {
|
||||
t.Fatalf("err = %v, want ErrDuplicatePartyID", err)
|
||||
}
|
||||
}
|
||||
|
||||
func TestAggregate_WrongCiphertext(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct1 := NewFHECiphertext([]byte("ciphertext-1"))
|
||||
ct2 := NewFHECiphertext([]byte("ciphertext-2"))
|
||||
sess := freshSession(t)
|
||||
|
||||
pd := NewPartialDecrypter()
|
||||
share, err := pd.PartialDecrypt(context.Background(), keys[0], ct1, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt: %v", err)
|
||||
}
|
||||
// Aggregate against the wrong ciphertext.
|
||||
pkMap := map[uint32]KeyShare{keys[0].PartyID: keys[0]}
|
||||
agg := NewShareAggregator()
|
||||
agg.PartyKeys = pkMap
|
||||
|
||||
_, _, err = agg.Aggregate(context.Background(), ct2, []FHEThresholdShare{share}, 1, sess)
|
||||
if err != ErrCiphertextIDMismatch {
|
||||
t.Fatalf("err = %v, want ErrCiphertextIDMismatch", err)
|
||||
}
|
||||
}
|
||||
|
||||
func TestVerifyShareWithKey_HappyPath(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-verify"))
|
||||
sess := freshSession(t)
|
||||
|
||||
pd := NewPartialDecrypter()
|
||||
share, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt: %v", err)
|
||||
}
|
||||
v := NewShareVerifier()
|
||||
ok, err := v.VerifyShareWithKey(context.Background(), share, ct, keys[0], sess)
|
||||
if err != nil || !ok {
|
||||
t.Fatalf("VerifyShareWithKey: ok=%v err=%v", ok, err)
|
||||
}
|
||||
}
|
||||
|
||||
func TestVerifyShare_PublicPathFailsWithoutCDS(t *testing.T) {
|
||||
// Documentation test: until the CDS proof ships, the public-key
|
||||
// verification path returns ErrNoiseProofVerify. This test
|
||||
// guards against accidental success — if it ever turns green
|
||||
// without a CDS implementation, the verifier has been weakened.
|
||||
keys, pubs := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-public-verify"))
|
||||
sess := freshSession(t)
|
||||
pd := NewPartialDecrypter()
|
||||
share, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt: %v", err)
|
||||
}
|
||||
v := NewShareVerifier()
|
||||
ok, err := v.VerifyShare(context.Background(), share, ct, pubs[0], sess)
|
||||
if err != ErrNoiseProofVerify || ok {
|
||||
t.Fatalf("VerifyShare: ok=%v err=%v, want false + ErrNoiseProofVerify", ok, err)
|
||||
}
|
||||
}
|
||||
|
||||
func TestComputeTranscriptRoot_OrderInvariant(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 3)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-transcript"))
|
||||
sess := freshSession(t)
|
||||
|
||||
shares := make([]FHEThresholdShare, 3)
|
||||
for i := 0; i < 3; i++ {
|
||||
pd := NewPartialDecrypter()
|
||||
s, err := pd.PartialDecrypt(context.Background(), keys[i], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt[%d]: %v", i, err)
|
||||
}
|
||||
shares[i] = s
|
||||
}
|
||||
pkMap := make(map[uint32]KeyShare)
|
||||
for _, k := range keys {
|
||||
pkMap[k.PartyID] = k
|
||||
}
|
||||
agg := NewShareAggregator()
|
||||
agg.PartyKeys = pkMap
|
||||
|
||||
res1, _, err := agg.Aggregate(context.Background(), ct, shares, 3, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("Aggregate: %v", err)
|
||||
}
|
||||
root1 := ComputeTranscriptRoot(sess, res1, shares)
|
||||
|
||||
// Reorder shares — transcript root MUST be byte-equal because the
|
||||
// transcript canonicalizes by ascending PartyID.
|
||||
reordered := []FHEThresholdShare{shares[2], shares[0], shares[1]}
|
||||
res2, _, err := agg.Aggregate(context.Background(), ct, reordered, 3, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("Aggregate reordered: %v", err)
|
||||
}
|
||||
root2 := ComputeTranscriptRoot(sess, res2, reordered)
|
||||
if root1 != root2 {
|
||||
t.Fatalf("transcript root not order-invariant:\n %x\n %x", root1, root2)
|
||||
}
|
||||
}
|
||||
|
||||
func TestNoiseProof_VersionTagged(t *testing.T) {
|
||||
keys, _ := makeCommittee(t, 1)
|
||||
ct := NewFHECiphertext([]byte("ciphertext-version"))
|
||||
sess := freshSession(t)
|
||||
pd := NewPartialDecrypter()
|
||||
share, err := pd.PartialDecrypt(context.Background(), keys[0], ct, sess)
|
||||
if err != nil {
|
||||
t.Fatalf("PartialDecrypt: %v", err)
|
||||
}
|
||||
if len(share.NoiseProof) < 8 {
|
||||
t.Fatalf("noise proof too short")
|
||||
}
|
||||
// Bump version → verification fails.
|
||||
share.NoiseProof[3] = 0xff
|
||||
share.ShareRoot = computeShareRoot(share, sess)
|
||||
if verifyNoiseProof(keys[0], share, sess) {
|
||||
t.Fatalf("expected version mismatch to fail verification")
|
||||
}
|
||||
}
|
||||
|
||||
func TestStatus_String(t *testing.T) {
|
||||
cases := []struct {
|
||||
s FHEStatus
|
||||
want string
|
||||
}{
|
||||
{StatusOK, "OK"},
|
||||
{StatusInsufficientShares, "InsufficientShares"},
|
||||
{StatusNoiseProofFailed, "NoiseProofFailed"},
|
||||
{StatusShareRootMismatch, "ShareRootMismatch"},
|
||||
{StatusReplay, "Replay"},
|
||||
{StatusUnknownParty, "UnknownParty"},
|
||||
{StatusInvalidCiphertext, "InvalidCiphertext"},
|
||||
{FHEStatus(255), "Unknown"},
|
||||
}
|
||||
for _, c := range cases {
|
||||
if got := c.s.String(); got != c.want {
|
||||
t.Errorf("FHEStatus(%d).String() = %q, want %q", c.s, got, c.want)
|
||||
}
|
||||
}
|
||||
}
|
||||
@@ -0,0 +1,206 @@
|
||||
// Canonical encoding + transcript-root construction for the threshold
|
||||
// FHE service.
|
||||
//
|
||||
// Two roots flow through the protocol:
|
||||
//
|
||||
// ShareRoot = sha256(canonicalShare(share, sessionID))
|
||||
// ThresholdTranscriptRoot = keccak256(canonicalTranscript(...))
|
||||
//
|
||||
// Both encodings are length-prefixed, fixed-byte-order, and reject
|
||||
// trailing data. Determinism across CPU/Metal/CUDA/Go/C++ implementations
|
||||
// is exactly the byte-equivalence of these encodings — the same input
|
||||
// MUST produce the same root on every backend. This is the
|
||||
// `compose_root` step of the MPCVM four-kernel template.
|
||||
//
|
||||
// The keccak256 used for the transcript root matches the EVM/Quasar
|
||||
// keccak shape so the FHEPrecompileArtifact.ThresholdTranscriptRoot
|
||||
// field can be checked inside the cevm precompile dispatcher without
|
||||
// converting hash families.
|
||||
//
|
||||
// Copyright (c) 2026, Lux Industries Inc.
|
||||
// SPDX-License-Identifier: BSD-3-Clause
|
||||
package threshold
|
||||
|
||||
import (
|
||||
"crypto/sha256"
|
||||
"encoding/binary"
|
||||
"errors"
|
||||
"sort"
|
||||
|
||||
"golang.org/x/crypto/sha3"
|
||||
)
|
||||
|
||||
// ErrCanonical is returned when canonical encoding fails. Indicates a
|
||||
// caller-side bug (over-large field, nil pointer) — never a wire-side
|
||||
// failure.
|
||||
var ErrCanonical = errors.New("threshold: canonical encoding failed")
|
||||
|
||||
// canonicalShare encodes a share + sessionID into the byte slice that
|
||||
// is sha256'd to produce ShareRoot.
|
||||
//
|
||||
// Layout (length-prefixed, big-endian):
|
||||
//
|
||||
// domain "LUX/FHE/THRESHOLD/SHARE/v1" (26 bytes)
|
||||
// partyID uint32 BE (4 bytes)
|
||||
// ctID fixed 32 bytes (32 bytes)
|
||||
// sessionID fixed 32 bytes (32 bytes)
|
||||
// shareLen uint32 BE (4 bytes)
|
||||
// shareData shareLen bytes
|
||||
//
|
||||
// NoiseProof is intentionally NOT in the share root: the noise proof
|
||||
// commits to the same transcript and is verified independently. Mixing
|
||||
// it into ShareRoot would force aggregators to re-encode the entire
|
||||
// proof to verify a single share's identity — wasteful and brittle.
|
||||
func canonicalShare(s FHEThresholdShare, sessionID [32]byte) []byte {
|
||||
const domain = "LUX/FHE/THRESHOLD/SHARE/v1"
|
||||
out := make([]byte, 0, len(domain)+4+32+32+4+len(s.ShareData))
|
||||
out = append(out, domain...)
|
||||
out = appendU32(out, s.PartyID)
|
||||
out = append(out, s.CiphertextID[:]...)
|
||||
out = append(out, sessionID[:]...)
|
||||
out = appendU32(out, uint32(len(s.ShareData)))
|
||||
out = append(out, s.ShareData...)
|
||||
return out
|
||||
}
|
||||
|
||||
// computeShareRoot returns sha256(canonicalShare(share, sessionID)).
|
||||
func computeShareRoot(s FHEThresholdShare, sessionID [32]byte) [32]byte {
|
||||
return sha256.Sum256(canonicalShare(s, sessionID))
|
||||
}
|
||||
|
||||
// canonicalTranscript encodes the full threshold-decryption transcript
|
||||
// into the byte slice that is keccak256'd to produce
|
||||
// ThresholdTranscriptRoot.
|
||||
//
|
||||
// Layout:
|
||||
//
|
||||
// domain "LUX/FHE/THRESHOLD/TRANSCRIPT/v1" (31 bytes)
|
||||
// sessionID fixed 32 bytes
|
||||
// ctRoot fixed 32 bytes (CiphertextRoot from result)
|
||||
// partyCount uint32 BE
|
||||
// threshold uint32 BE
|
||||
// shareCount uint32 BE
|
||||
// shareRoots shareCount × 32 bytes (ascending PartyID order)
|
||||
// aggregateRoot fixed 32 bytes
|
||||
// statusU32 uint32 BE
|
||||
//
|
||||
// The sort-on-PartyID step is what makes the transcript byte-equal
|
||||
// across nodes that may receive shares in different network orders.
|
||||
func canonicalTranscript(
|
||||
sessionID [32]byte,
|
||||
result FHEThresholdResult,
|
||||
shareRoots [][32]byte,
|
||||
) []byte {
|
||||
const domain = "LUX/FHE/THRESHOLD/TRANSCRIPT/v1"
|
||||
out := make([]byte, 0, len(domain)+32+32+4+4+4+len(shareRoots)*32+32+4)
|
||||
out = append(out, domain...)
|
||||
out = append(out, sessionID[:]...)
|
||||
out = append(out, result.CiphertextRoot[:]...)
|
||||
out = appendU32(out, result.PartyCount)
|
||||
out = appendU32(out, result.Threshold)
|
||||
out = appendU32(out, uint32(len(shareRoots)))
|
||||
for _, sr := range shareRoots {
|
||||
out = append(out, sr[:]...)
|
||||
}
|
||||
out = append(out, result.AggregateRoot[:]...)
|
||||
out = appendU32(out, uint32(result.Status))
|
||||
return out
|
||||
}
|
||||
|
||||
// ComputeTranscriptRoot returns keccak256(canonicalTranscript(...)).
|
||||
//
|
||||
// This is the value that flows into
|
||||
// FHEPrecompileArtifact.ThresholdTranscriptRoot and is anchored by the
|
||||
// audit dispatcher (M-Chain in primary mode, local WORM in private
|
||||
// mode).
|
||||
func ComputeTranscriptRoot(
|
||||
sessionID [32]byte,
|
||||
result FHEThresholdResult,
|
||||
shares []FHEThresholdShare,
|
||||
) [32]byte {
|
||||
roots := make([][32]byte, len(shares))
|
||||
idxs := make([]int, len(shares))
|
||||
for i := range shares {
|
||||
idxs[i] = i
|
||||
}
|
||||
sort.Slice(idxs, func(a, b int) bool {
|
||||
return shares[idxs[a]].PartyID < shares[idxs[b]].PartyID
|
||||
})
|
||||
for i, idx := range idxs {
|
||||
roots[i] = shares[idx].ShareRoot
|
||||
}
|
||||
h := sha3.NewLegacyKeccak256()
|
||||
h.Write(canonicalTranscript(sessionID, result, roots))
|
||||
var out [32]byte
|
||||
copy(out[:], h.Sum(nil))
|
||||
return out
|
||||
}
|
||||
|
||||
// merkleShareRoot computes the Merkle root over share roots in
|
||||
// ascending PartyID order. Used to populate
|
||||
// FHEThresholdResult.ShareRoot. Pure sha256-of-pairs; matches the
|
||||
// gpukit transcript_root primitive's CPU oracle.
|
||||
func merkleShareRoot(shares []FHEThresholdShare) [32]byte {
|
||||
if len(shares) == 0 {
|
||||
return [32]byte{}
|
||||
}
|
||||
idxs := make([]int, len(shares))
|
||||
for i := range shares {
|
||||
idxs[i] = i
|
||||
}
|
||||
sort.Slice(idxs, func(a, b int) bool {
|
||||
return shares[idxs[a]].PartyID < shares[idxs[b]].PartyID
|
||||
})
|
||||
leaves := make([][32]byte, len(idxs))
|
||||
for i, idx := range idxs {
|
||||
leaves[i] = shares[idx].ShareRoot
|
||||
}
|
||||
for len(leaves) > 1 {
|
||||
next := make([][32]byte, 0, (len(leaves)+1)/2)
|
||||
for i := 0; i < len(leaves); i += 2 {
|
||||
var pair [64]byte
|
||||
copy(pair[:32], leaves[i][:])
|
||||
if i+1 < len(leaves) {
|
||||
copy(pair[32:], leaves[i+1][:])
|
||||
} else {
|
||||
copy(pair[32:], leaves[i][:])
|
||||
}
|
||||
next = append(next, sha256.Sum256(pair[:]))
|
||||
}
|
||||
leaves = next
|
||||
}
|
||||
return leaves[0]
|
||||
}
|
||||
|
||||
// ciphertextRoot computes sha256 of the ciphertext bytes — the value
|
||||
// stored on FHECiphertext.ID at construction and reused as
|
||||
// FHEThresholdResult.CiphertextRoot for single-input decrypts.
|
||||
func ciphertextRoot(ct FHECiphertext) [32]byte {
|
||||
return sha256.Sum256(ct.Bytes)
|
||||
}
|
||||
|
||||
// canonicalAggregate encodes the plaintext + party-count + threshold
|
||||
// into the byte slice that is sha256'd to produce AggregateRoot. Used
|
||||
// by the aggregator to commit to the output without revealing it
|
||||
// upstream.
|
||||
func canonicalAggregate(plaintext []byte, partyCount, threshold uint32) []byte {
|
||||
const domain = "LUX/FHE/THRESHOLD/AGGREGATE/v1"
|
||||
out := make([]byte, 0, len(domain)+4+len(plaintext)+4+4)
|
||||
out = append(out, domain...)
|
||||
out = appendU32(out, uint32(len(plaintext)))
|
||||
out = append(out, plaintext...)
|
||||
out = appendU32(out, partyCount)
|
||||
out = appendU32(out, threshold)
|
||||
return out
|
||||
}
|
||||
|
||||
// computeAggregateRoot returns sha256(canonicalAggregate(...)).
|
||||
func computeAggregateRoot(plaintext []byte, partyCount, threshold uint32) [32]byte {
|
||||
return sha256.Sum256(canonicalAggregate(plaintext, partyCount, threshold))
|
||||
}
|
||||
|
||||
func appendU32(b []byte, v uint32) []byte {
|
||||
var tmp [4]byte
|
||||
binary.BigEndian.PutUint32(tmp[:], v)
|
||||
return append(b, tmp[:]...)
|
||||
}
|
||||
@@ -0,0 +1,200 @@
|
||||
// Package threshold implements the t-of-n threshold FHE service layer
|
||||
// — partial decryption, share verification, and aggregate decryption —
|
||||
// composed on top of luxfi/fhe primitives (NTT, blind rotation, key
|
||||
// switching).
|
||||
//
|
||||
// The package is independent of any single FHE scheme: the service
|
||||
// interfaces accept opaque ciphertext bytes and party-keyed share
|
||||
// material, and the concrete implementations in this package target the
|
||||
// TFHE/FHEW path used by F-Chain. Other schemes (BFV, CKKS, BGV) plug in
|
||||
// by implementing the same interfaces.
|
||||
//
|
||||
// Design discipline:
|
||||
//
|
||||
// - Every wire object — share, transcript, aggregate — carries a
|
||||
// canonical sha256 root of its inputs. Verification and aggregation
|
||||
// re-derive these roots; mismatches fail closed with a typed status.
|
||||
//
|
||||
// - Partial decryption follows the MPCVM v0.62 four-kernel template:
|
||||
// `apply` decomposes the ciphertext into per-party operands;
|
||||
// `sweep` samples per-share noise and updates the Fiat-Shamir
|
||||
// transcript; `compute_leaves` produces the per-party share + noise
|
||||
// proof; `compose_root` keccaks the canonical encoding and emits the
|
||||
// ShareRoot. Each step has a single, unambiguous shape.
|
||||
//
|
||||
// - The package targets the dual-mode MPC dispatcher (sibling #115):
|
||||
// primary mode anchors the ThresholdTranscriptRoot to M-Chain; private
|
||||
// mode anchors to local WORM. The service emits the root either way;
|
||||
// the caller decides where it lands.
|
||||
//
|
||||
// Reference: LP-137-FHE-THRESHOLD.md.
|
||||
//
|
||||
// Copyright (c) 2026, Lux Industries Inc.
|
||||
// SPDX-License-Identifier: BSD-3-Clause
|
||||
package threshold
|
||||
|
||||
// FHEStatus is the verdict status emitted by the threshold service for
|
||||
// every share, transcript, and aggregate result. Wire stable: enum
|
||||
// values are fixed and MUST NOT be reordered. Add new statuses by
|
||||
// appending.
|
||||
type FHEStatus uint32
|
||||
|
||||
const (
|
||||
// StatusOK is the success status. The result fields are valid and the
|
||||
// plaintext (where present) is the correct decryption.
|
||||
StatusOK FHEStatus = 0
|
||||
|
||||
// StatusInsufficientShares indicates fewer than `Threshold` valid
|
||||
// shares were collected before aggregation. The result is undefined.
|
||||
StatusInsufficientShares FHEStatus = 1
|
||||
|
||||
// StatusNoiseProofFailed indicates a share's noise proof did not
|
||||
// verify against the Fiat-Shamir transcript. The share has been
|
||||
// rejected; the aggregate excludes it.
|
||||
StatusNoiseProofFailed FHEStatus = 2
|
||||
|
||||
// StatusShareRootMismatch indicates the canonical encoding of a
|
||||
// share's data does not match its declared ShareRoot. Indicates
|
||||
// tampering or serialization drift.
|
||||
StatusShareRootMismatch FHEStatus = 3
|
||||
|
||||
// StatusReplay indicates a sessionID has already been used for
|
||||
// partial decryption. The service refuses to re-issue a share for
|
||||
// the same (party, ciphertext, sessionID) tuple.
|
||||
StatusReplay FHEStatus = 4
|
||||
|
||||
// StatusUnknownParty indicates a share carried a PartyID outside
|
||||
// the configured set. The aggregator rejects it before verification.
|
||||
StatusUnknownParty FHEStatus = 5
|
||||
|
||||
// StatusInvalidCiphertext indicates the input ciphertext failed
|
||||
// scheme-level structural validation (header drift, length mismatch,
|
||||
// modulus mismatch).
|
||||
StatusInvalidCiphertext FHEStatus = 6
|
||||
)
|
||||
|
||||
// String returns a stable, human-readable name for the status.
|
||||
func (s FHEStatus) String() string {
|
||||
switch s {
|
||||
case StatusOK:
|
||||
return "OK"
|
||||
case StatusInsufficientShares:
|
||||
return "InsufficientShares"
|
||||
case StatusNoiseProofFailed:
|
||||
return "NoiseProofFailed"
|
||||
case StatusShareRootMismatch:
|
||||
return "ShareRootMismatch"
|
||||
case StatusReplay:
|
||||
return "Replay"
|
||||
case StatusUnknownParty:
|
||||
return "UnknownParty"
|
||||
case StatusInvalidCiphertext:
|
||||
return "InvalidCiphertext"
|
||||
default:
|
||||
return "Unknown"
|
||||
}
|
||||
}
|
||||
|
||||
// FHEThresholdShare is a single party's contribution to a threshold
|
||||
// decryption (or partial evaluation). It is the wire object produced by
|
||||
// PartialDecryptService.PartialDecrypt and consumed by both
|
||||
// ShareVerifyService.VerifyShare and ShareAggregateService.Aggregate.
|
||||
//
|
||||
// The ShareRoot field binds (PartyID, CiphertextID, ShareData) to a
|
||||
// single sha256 hash so downstream verifiers can detect replay,
|
||||
// reordering, and field-level tampering with a single comparison.
|
||||
type FHEThresholdShare struct {
|
||||
// PartyID is the 1-indexed party identifier. Party indices are part
|
||||
// of the keygen ceremony — every share for a given ciphertext must
|
||||
// carry a distinct PartyID.
|
||||
PartyID uint32
|
||||
|
||||
// CiphertextID is the sha256 of the canonical encoding of the
|
||||
// ciphertext this share decrypts. Allows the aggregator to reject
|
||||
// mismatched-ciphertext shares without re-decoding.
|
||||
CiphertextID [32]byte
|
||||
|
||||
// ShareData is the scheme-specific share payload — for TFHE this is
|
||||
// (b · sk_i + e_i) mod q packed as the canonical scheme bytes; for
|
||||
// BFV/CKKS this is the partial-decrypt polynomial. The threshold
|
||||
// package does not interpret the bytes; the FHEScheme bound at the
|
||||
// service layer does.
|
||||
ShareData []byte
|
||||
|
||||
// NoiseProof is the proof that the noise added during partial
|
||||
// decryption was sampled from the prescribed distribution within
|
||||
// the protocol-mandated bound. Production systems use a CDS-style
|
||||
// sigma-of-knowledge proof; see noise_proof.go for the reference
|
||||
// transcript construction.
|
||||
NoiseProof []byte
|
||||
|
||||
// ShareRoot is sha256(canonical(ShareData || PartyID || CiphertextID
|
||||
// || SessionID)). Verifiers MUST re-derive and compare; aggregators
|
||||
// MUST reject any share whose ShareRoot does not match.
|
||||
ShareRoot [32]byte
|
||||
}
|
||||
|
||||
// FHEThresholdResult is the aggregate of a threshold decryption: the
|
||||
// roots that flow into FHEPrecompileArtifact.ThresholdTranscriptRoot,
|
||||
// the party count and threshold actually realized, and the verdict
|
||||
// status.
|
||||
//
|
||||
// The aggregate plaintext (when Status == StatusOK) is returned out of
|
||||
// band by the aggregate service so callers can decide whether to log,
|
||||
// audit, or deliver it. The result struct itself only carries the roots
|
||||
// — those are the values bound into the precompile artifact and the
|
||||
// audit dispatcher.
|
||||
type FHEThresholdResult struct {
|
||||
// CiphertextRoot is sha256(canonical(input ciphertexts in canonical
|
||||
// order)). For single-ciphertext decrypts this is sha256 of the
|
||||
// ciphertext bytes; for multi-ciphertext aggregates (e.g. a vector
|
||||
// decrypt) it is the Merkle root.
|
||||
CiphertextRoot [32]byte
|
||||
|
||||
// ShareRoot is the Merkle root over all share roots used in the
|
||||
// aggregation, in canonical (ascending PartyID) order.
|
||||
ShareRoot [32]byte
|
||||
|
||||
// AggregateRoot is sha256(canonical(plaintext bytes || PartyCount ||
|
||||
// Threshold)). Callers anchoring to M-Chain or WORM use this as the
|
||||
// commitment to the aggregate output without revealing the plaintext.
|
||||
AggregateRoot [32]byte
|
||||
|
||||
// PartyCount is the number of valid shares actually combined.
|
||||
PartyCount uint32
|
||||
|
||||
// Threshold is the t value the protocol was configured for.
|
||||
Threshold uint32
|
||||
|
||||
// Status is the final verdict. StatusOK means the aggregate is valid
|
||||
// and the out-of-band plaintext bytes are the true decryption.
|
||||
Status FHEStatus
|
||||
}
|
||||
|
||||
// KeyShare is a single party's secret share of the threshold key. The
|
||||
// Bytes field is the scheme-specific encoding; the threshold package
|
||||
// does not interpret it. PartyID matches FHEThresholdShare.PartyID.
|
||||
type KeyShare struct {
|
||||
PartyID uint32
|
||||
Bytes []byte
|
||||
}
|
||||
|
||||
// PublicKey is the per-party public verification material. For TFHE
|
||||
// threshold this is the party's public commitment to its secret share;
|
||||
// for BFV/CKKS it is the public part of the partial-decrypt key.
|
||||
type PublicKey struct {
|
||||
PartyID uint32
|
||||
Bytes []byte
|
||||
}
|
||||
|
||||
// FHECiphertext is the opaque wire form of an FHE ciphertext. The
|
||||
// threshold package treats it as immutable bytes plus a 32-byte ID; the
|
||||
// scheme-specific decoder is plugged in via the service constructor.
|
||||
type FHECiphertext struct {
|
||||
// ID is sha256 of Bytes. Computed once at construction; aggregators
|
||||
// re-check before use.
|
||||
ID [32]byte
|
||||
|
||||
// Bytes is the canonical scheme-specific encoding.
|
||||
Bytes []byte
|
||||
}
|
||||
Reference in New Issue
Block a user