3.0 KiB
PARAMS — FROST (Lux Profile)
Parameter-set registry for the Lux FROST profile. Pinned ciphersuites, threshold ranges, transcript-binding tags.
§1 Pinned ciphersuites
The Lux profile deploys exactly two ciphersuites:
1.1 FROST(Ed25519, SHA-512)
| Field | Value |
|---|---|
| Group | edwards25519 (curve25519 Edwards form) |
| Group order | 2^252 + 27742317777372353535851937790883648493 |
| Hash | SHA-512 |
| Transcript-binding tag | lux-frost-ed25519-v1 |
| Signature size | 64 bytes (compressed point + scalar) |
| LP | LP-4711 |
| Single-party verifier | crypto/ed25519 (Go stdlib) |
1.2 FROST(secp256k1, SHA-256) + Taproot
| Field | Value |
|---|---|
| Group | secp256k1 |
| Group order | 2^256 - 432420386565659656852420866394968145599 (curve order n) |
| Hash | SHA-256 |
| Transcript-binding tag | lux-frost-secp256k1-taproot-v1 |
| Signature size | 64 bytes (x-only point + scalar, BIP-340) |
| LP | LP-4712 |
| Single-party verifier | BIP-340 Taproot verification |
§2 Threshold ranges
Lux FROST instances must satisfy:
1 ≤ t ≤ n ≤ 1024
t ≥ 2 (single-signer is not a threshold scheme)
Configurations outside this range are rejected by keygen/ with
a typed error.
2.1 Recommended operating points
| Use case | Pinned (t, n) | Rationale |
|---|---|---|
| Lux bridge custody | (3, 5) | High availability with 60% Byzantine tolerance |
| Validator multi-sig | (5, 7) | Maps to 5-of-7 Lux validator default |
| Federated DEX custody | (7, 10) | Wider committee, same tolerance |
| Cross-chain relay | (4, 7) | Matches lss_frost.go defaults |
These are recommendations, not normative. Deployments may choose
any (t, n) within §2.
§3 Other parameters
3.1 Round count
FROST is a 2-round protocol:
- Round 1: commit (per-signer nonces)
- Round 2: reveal (per-signer signature shares)
The Lux profile does NOT add additional rounds.
3.2 Pre-processing (optional)
Round-1 commitments may be pre-computed in advance per Komlo- Goldberg §6. The Lux production deployments do NOT use pre-processing (round-1 commits are session-bound for replay prevention); pre-processing is an opt-in flag.
3.3 Identifiable abort
Round-2 share verification is mandatory and enforced by sign/.
There is no opt-out.
§4 Out-of-scope parameters
The following are CFRG draft parameters that the Lux profile pins specifically and does NOT make configurable:
- Hash output truncation
- Nonce-generation entropy budget (mandated full-entropy per round)
- DKG protocol (Lux uses its own DKG via
keygen/mirroring CFRG guidance, not a separate trusted-dealer mode)
§5 Cross-references
SPEC.md— protocol specREADME.md— overview + Tier label- LP-4710 / LP-4711 / LP-4712 / LP-4700
- Upstream: Komlo-Goldberg 2020 +
draft-irtf-cfrg-frost