Files
proofs/lean/Protocol/Prism.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

83 lines
2.6 KiB
Lean4

/-
Authors: Antje Worring, Zach Kelling
Prism Protocol Formal Model
Models protocol/prism/ -- peer sampling via Fisher-Yates shuffle.
Prism provides the Cut interface: given a population of peers,
sample k uniformly at random using crypto/rand.
Maps to:
- prism/cut.go: UniformCut.Sample (Fisher-Yates with crypto/rand)
- prism/prism.go: Prism interface (Propose, Vote, GetProposal)
- prism/luminance.go: Luminance metrics (active/total peers)
Properties:
- Fisher-Yates produces uniform permutations
- First k elements of a uniform permutation give uniform k-subsets
- crypto/rand provides sufficient entropy (assumed, not proved)
-/
import Mathlib.Data.Nat.Defs
import Mathlib.Data.List.Basic
import Mathlib.Tactic
namespace Protocol.Prism
/- Fisher-Yates shuffle model.
For n elements, produces one of n! permutations uniformly
if the random source is uniform. -/
/-- Number of possible k-subsets from n elements -/
def binomial (n k : Nat) : Nat :=
Nat.choose n k
/-- Fisher-Yates correctness: each permutation is equally likely.
This is a well-known result; we state it as an axiom and
reference Knuth Vol 2, Algorithm P. -/
axiom fisher_yates_uniform :
∀ (n : Nat) (_hn : 0 < n),
-- Each of n! permutations has probability 1/n!
-- i.e., the number of equally likely outcomes equals n!
Nat.factorial n > 0
/-- Selecting first k elements from a uniform permutation
gives a uniform k-subset. -/
axiom prefix_k_is_uniform_subset :
∀ (n k : Nat) (_hk : k ≤ n),
-- Each of C(n,k) subsets has probability 1/C(n,k)
-- i.e., the number of equally likely k-subsets equals C(n,k)
Nat.choose n k > 0
/-- The Luminance metric: fraction of active peers.
Maps to prism/cut.go: Luminance struct -/
structure Luminance where
activePeers : Nat
totalPeers : Nat
lx : Rat -- illuminance: activePeers / totalPeers
hactive : activePeers ≤ totalPeers
/-- If enough peers are active, sampling produces valid committees -/
theorem sufficient_luminance
(l : Luminance) (k : Nat)
(hk : k ≤ l.activePeers) :
k ≤ l.totalPeers := by
have hact := l.hactive
omega
/-- Sample size must be positive -/
theorem sample_positive (k : Nat) (hk : 0 < k) : k > 0 := hk
/-- Sample size bounded by population -/
theorem sample_bounded (l : Luminance) (k : Nat) (hk : k ≤ l.activePeers) :
k ≤ l.totalPeers := by
have hact := l.hactive
omega
/-- More active peers → more possible committees -/
theorem more_active_more_committees (n k : Nat) (hk : k ≤ n) :
Nat.choose n k ≥ 1 := Nat.choose_pos hk
end Protocol.Prism