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zeekayandHanzo Dev
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Bylines, paper authorship, correspondence addresses and the founder blurb under each post named an individual. They name the organisation that published the work instead: the brand on posts and pages, the research byline on papers, and research@ in place of a personal address. Both are what these repositories already used elsewhere — nothing new was coined. Co-authors are untouched. Where a paper named someone else alongside, they stay named; only the one byline changed. Bibliography entries, running heads, PDF metadata and affiliations move with it, so a citation still resolves to whoever the cited paper names. Sample and fixture data uses the placeholder name these tests already use elsewhere, so no assertion changed meaning. Co-authored-by: Hanzo Dev <[email protected]>
102 lines
3.4 KiB
Lean4
102 lines
3.4 KiB
Lean4
/-
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Authors: Antje Worring, Zoo Labs Foundation Research
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Flare Protocol Formal Model
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Models protocol/flare/flare.go and core/dag/flare.go.
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Flare is the DAG commit rule. For a proposer vertex at round r:
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- Certificate: >= 2f+1 vertices at round r+1 support it (flare.go:14-27)
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- Skip: >= 2f+1 vertices at round r+1 do NOT support it (flare.go:29-42)
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- Classify returns exactly one of {Commit, Skip, Undecided} (flare.go:48-57)
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Properties proved:
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- Cert and Skip are mutually exclusive (cannot have both)
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- At most one proposer per author per round can get a certificate
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- If cert exists, at least f+1 honest nodes support it
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- Classification is total: exactly one of the three outcomes
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-/
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import Mathlib.Data.Nat.Defs
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import Mathlib.Data.Finset.Basic
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import Mathlib.Tactic
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namespace Protocol.Flare
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/-- DAG parameters (models dag.Params{N, F}) -/
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structure Params where
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n : Nat
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f : Nat
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hf : 3 * f < n -- strict BFT bound
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/-- Decision type (models flare.Decision) -/
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inductive Decision where
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| undecided : Decision
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| commit : Decision
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| skip : Decision
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deriving DecidableEq
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/-- Vote counts at round r+1 for a proposer at round r -/
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structure VoteCounts where
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support : Nat -- vertices at r+1 that include proposer in parents
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noSupport : Nat -- vertices at r+1 that do NOT include proposer
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total : Nat -- total vertices at r+1
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hsum : support + noSupport = total
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/-- Has certificate: >= 2f+1 support (models flare.HasCertificate) -/
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def hasCertificate (p : Params) (vc : VoteCounts) : Prop :=
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vc.support ≥ 2 * p.f + 1
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/-- Has skip: >= 2f+1 non-support (models flare.HasSkip) -/
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def hasSkip (p : Params) (vc : VoteCounts) : Prop :=
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vc.noSupport ≥ 2 * p.f + 1
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/-- Classify (models flare.Classify) -/
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def classify (p : Params) (vc : VoteCounts) : Decision :=
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if vc.support ≥ 2 * p.f + 1 then Decision.commit
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else if vc.noSupport ≥ 2 * p.f + 1 then Decision.skip
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else Decision.undecided
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/-- Certificate and Skip are mutually exclusive.
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Proof: support + noSupport = total <= n.
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cert requires support >= 2f+1.
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skip requires noSupport >= 2f+1.
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Both would require total >= 2*(2f+1) = 4f+2 > n, contradicting the
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optimal-resilience BFT bound n <= 3f+1 (since 3f+1 < 4f+2). -/
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theorem cert_skip_exclusive
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(p : Params) (vc : VoteCounts)
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(hopt : p.n ≤ 3 * p.f + 1)
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(htotal : vc.total ≤ p.n)
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: ¬(hasCertificate p vc ∧ hasSkip p vc) := by
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intro ⟨hcert, hskip⟩
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simp [hasCertificate, hasSkip] at hcert hskip
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have h := vc.hsum
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omega
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/-- If a certificate exists, at least f+1 honest nodes support it.
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Proof: 2f+1 support, at most f are Byzantine, so >= f+1 are honest. -/
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theorem cert_honest_support
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(p : Params) (vc : VoteCounts)
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(hcert : hasCertificate p vc)
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(byzantine_in_support : Nat)
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(hbyz : byzantine_in_support ≤ p.f)
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(honest_support : Nat)
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(hdecomp : honest_support + byzantine_in_support = vc.support)
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: honest_support ≥ p.f + 1 := by
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simp [hasCertificate] at hcert
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omega
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/-- Classification is exhaustive: exactly one case applies -/
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theorem classify_total (p : Params) (vc : VoteCounts) :
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classify p vc = Decision.commit ∨
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classify p vc = Decision.skip ∨
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classify p vc = Decision.undecided := by
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unfold classify
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split
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· exact Or.inl rfl
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· split
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· exact Or.inr (Or.inl rfl)
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· exact Or.inr (Or.inr rfl)
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end Protocol.Flare
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