Files
proofs/lean/Crypto/SLHDSA.lean
zooqueenandHanzo Dev d3bff5e2dc proofs: drive Lean library to 0 errors, eliminate proof-by-assumption axioms
The lean/ proof library (88 files) had ~180 type-check errors across ~45 files
plus 31 proof-by-assumption axiom cheats. It now type-checks cleanly under
Lean 4.14.0 + Mathlib, with every theorem genuinely proven from definitions.

Errors fixed:
- Stale Mathlib imports: Data.Nat.Basic / Data.Int.Basic were removed this rev
  -> Data.Nat.Defs / Data.Int.Defs (57 files).
- Shared AI/Agent/Governance/Contract/DeFi/Ecology draft files: same proof-rot
  as the zoo-labs sibling library (now reconciled): omega missing in-scope
  bounds, dead tactics after simp, simp over-reduction, doc-comment placement,
  reserved-word binders, deriving Repr on Finset-bearing structs, noncomputable
  defs over opaque primitives.
- Consensus/Liveness: collapsed a 74-error cascade (undefined shared state model
  inlined from Safety.lean; the |>. pipe-projection vs comparison parse trap on
  14 lines rewritten to explicit dot projection).
- Crypto (BLS/FROST/Corona/Hybrid/threshold/FHE), Consensus, Protocol, Warp,
  Trust, GPU, Compute, Network, DeFi: brought structure invariants into scope
  for omega, Nat-division bounds via Nat.div_le_of_le_mul / Nat.div_mul_le_self,
  noncomputable over opaque crypto ops, deriving Inhabited for index access.

Integrity:
- Removed all 31 `theorem X := X_ax` cheats (axiom asserting the identical
  statement) and proved each from definitions; removed the UNSOUND
  content_addressed axiom (hash-injectivity over a struct with free fields).
- Quorum-intersection theorems (BFT/Quasar/Flare/Warp/BLS/GPU/Bridge): the draft
  hypothesis 3f<n is insufficient (n unbounded above makes them false); tightened
  to the optimal-resilience invariant n=3f+1 / 2t>n. Statement intent preserved.
- Net axiom change: -35 / +1 (the one addition, honesty_static, is a
  fixed-validator-set modeling assumption matching sibling files).
- Remaining axioms are trusted-base only: opaque crypto primitives (groups,
  pairings, hardness, hashes, FHE encrypt/decrypt, BLS soundness, forward
  secrecy, Fisher-Yates uniformity) and protocol modeling assumptions. No
  sorry/admit/native_decide. Verified all theorems trace to
  [propext, Classical.choice, Quot.sound] plus those primitives.

Co-authored-by: Hanzo Dev <[email protected]>
2026-06-02 05:54:28 -07:00

90 lines
2.8 KiB
Lean4

/-
Authors: Antje Worring, Zach Kelling
SLH-DSA (FIPS 205) Hash-Based Signature Correctness
The conservative backup in the hybrid scheme. SLH-DSA's security
relies ONLY on hash function properties — no lattice assumptions.
If ML-DSA falls to quantum or classical attack, SLH-DSA survives.
Based on SPHINCS+ (stateless hash-based signatures).
Maps to:
- luxfi/crypto: slhdsa package
- lux/node: validator hybrid identity (third signature)
Properties:
- Correctness: sign then verify succeeds
- Hash-only security: no lattice/group assumptions
- Stateless: no state tracking between signatures (unlike XMSS)
-/
import Mathlib.Data.Nat.Defs
import Mathlib.Tactic
namespace Crypto.SLHDSA
/-- SLH-DSA parameter sets (FIPS 205) -/
inductive ParamSet where
| slh128s -- SLH-DSA-SHA2-128s (small, slow)
| slh128f -- SLH-DSA-SHA2-128f (fast, larger)
| slh192s -- SLH-DSA-SHA2-192s
| slh256s -- SLH-DSA-SHA2-256s (maximum security)
deriving DecidableEq, Repr
/-- Signature sizes (bytes) -/
def sigSize : ParamSet → Nat
| .slh128s => 7856
| .slh128f => 17088
| .slh192s => 16224
| .slh256s => 29792
/-- Public key sizes (bytes) -/
def pkSize : ParamSet → Nat
| .slh128s => 32
| .slh128f => 32
| .slh192s => 48
| .slh256s => 64
/-- Security level (bits) -/
def securityBits : ParamSet → Nat
| .slh128s => 128
| .slh128f => 128
| .slh192s => 192
| .slh256s => 256
/-- Sign and verify (axiomatized) -/
axiom slhdsa_sign : ParamSet → Nat → Nat → Nat
axiom slhdsa_verify : ParamSet → Nat → Nat → Nat → Bool
/-- Correctness: valid keypair sign-then-verify succeeds -/
axiom slhdsa_correctness :
∀ (ps : ParamSet) (sk pk msg : Nat),
slhdsa_verify ps pk msg (slhdsa_sign ps sk msg) = true
/-- Hash-only security: security reduces to hash function properties.
No lattice, no discrete log, no factoring assumption. -/
axiom slhdsa_hash_only_security :
∀ (ps : ParamSet) (pk msg forgery : Nat),
slhdsa_verify ps pk msg forgery = true →
∃ (sk : Nat), forgery = slhdsa_sign ps sk msg
/-- 128s is the smallest signature -/
theorem slh128s_smallest : ∀ ps : ParamSet, sigSize .slh128s ≤ sigSize ps := by
intro ps; cases ps <;> simp [sigSize]
/-- All parameter sets have ≥ 128-bit security -/
theorem min_security_128 : ∀ ps : ParamSet, securityBits ps ≥ 128 := by
intro ps; cases ps <;> simp [securityBits]
/-- Public keys are compact (≤ 64 bytes) -/
theorem pk_compact : ∀ ps : ParamSet, pkSize ps ≤ 64 := by
intro ps; cases ps <;> simp [pkSize]
/-- Statelessness: signing is a pure function of (params, sk, msg).
No counter, no state tree updates. This is rfl by construction. -/
theorem stateless_signing (ps : ParamSet) (sk msg : Nat) :
slhdsa_sign ps sk msg = slhdsa_sign ps sk msg := rfl
end Crypto.SLHDSA