Files
proofs/lean/Protocol/Flare.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

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/-
Authors: Antje Worring, Zach Kelling
Flare Protocol Formal Model
Models protocol/flare/flare.go and core/dag/flare.go.
Flare is the DAG commit rule. For a proposer vertex at round r:
- Certificate: >= 2f+1 vertices at round r+1 support it (flare.go:14-27)
- Skip: >= 2f+1 vertices at round r+1 do NOT support it (flare.go:29-42)
- Classify returns exactly one of {Commit, Skip, Undecided} (flare.go:48-57)
Properties proved:
- Cert and Skip are mutually exclusive (cannot have both)
- At most one proposer per author per round can get a certificate
- If cert exists, at least f+1 honest nodes support it
- Classification is total: exactly one of the three outcomes
-/
import Mathlib.Data.Nat.Defs
import Mathlib.Data.Finset.Basic
import Mathlib.Tactic
namespace Protocol.Flare
/-- DAG parameters (models dag.Params{N, F}) -/
structure Params where
n : Nat
f : Nat
hf : 3 * f < n -- strict BFT bound
/-- Decision type (models flare.Decision) -/
inductive Decision where
| undecided : Decision
| commit : Decision
| skip : Decision
deriving DecidableEq
/-- Vote counts at round r+1 for a proposer at round r -/
structure VoteCounts where
support : Nat -- vertices at r+1 that include proposer in parents
noSupport : Nat -- vertices at r+1 that do NOT include proposer
total : Nat -- total vertices at r+1
hsum : support + noSupport = total
/-- Has certificate: >= 2f+1 support (models flare.HasCertificate) -/
def hasCertificate (p : Params) (vc : VoteCounts) : Prop :=
vc.support ≥ 2 * p.f + 1
/-- Has skip: >= 2f+1 non-support (models flare.HasSkip) -/
def hasSkip (p : Params) (vc : VoteCounts) : Prop :=
vc.noSupport ≥ 2 * p.f + 1
/-- Classify (models flare.Classify) -/
def classify (p : Params) (vc : VoteCounts) : Decision :=
if vc.support ≥ 2 * p.f + 1 then Decision.commit
else if vc.noSupport ≥ 2 * p.f + 1 then Decision.skip
else Decision.undecided
/-- Certificate and Skip are mutually exclusive.
Proof: support + noSupport = total <= n.
cert requires support >= 2f+1.
skip requires noSupport >= 2f+1.
Both would require total >= 2*(2f+1) = 4f+2 > n, contradicting the
optimal-resilience BFT bound n <= 3f+1 (since 3f+1 < 4f+2). -/
theorem cert_skip_exclusive
(p : Params) (vc : VoteCounts)
(hopt : p.n ≤ 3 * p.f + 1)
(htotal : vc.total ≤ p.n)
: ¬(hasCertificate p vc ∧ hasSkip p vc) := by
intro ⟨hcert, hskip⟩
simp [hasCertificate, hasSkip] at hcert hskip
have h := vc.hsum
omega
/-- If a certificate exists, at least f+1 honest nodes support it.
Proof: 2f+1 support, at most f are Byzantine, so >= f+1 are honest. -/
theorem cert_honest_support
(p : Params) (vc : VoteCounts)
(hcert : hasCertificate p vc)
(byzantine_in_support : Nat)
(hbyz : byzantine_in_support ≤ p.f)
(honest_support : Nat)
(hdecomp : honest_support + byzantine_in_support = vc.support)
: honest_support ≥ p.f + 1 := by
simp [hasCertificate] at hcert
omega
/-- Classification is exhaustive: exactly one case applies -/
theorem classify_total (p : Params) (vc : VoteCounts) :
classify p vc = Decision.commit ∨
classify p vc = Decision.skip ∨
classify p vc = Decision.undecided := by
unfold classify
split
· exact Or.inl rfl
· split
· exact Or.inr (Or.inl rfl)
· exact Or.inr (Or.inr rfl)
end Protocol.Flare