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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]>
83 lines
2.6 KiB
Lean4
83 lines
2.6 KiB
Lean4
/-
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Authors: Antje Worring, Zoo Labs Foundation Research
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Prism Protocol Formal Model
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Models protocol/prism/ -- peer sampling via Fisher-Yates shuffle.
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Prism provides the Cut interface: given a population of peers,
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sample k uniformly at random using crypto/rand.
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Maps to:
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- prism/cut.go: UniformCut.Sample (Fisher-Yates with crypto/rand)
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- prism/prism.go: Prism interface (Propose, Vote, GetProposal)
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- prism/luminance.go: Luminance metrics (active/total peers)
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Properties:
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- Fisher-Yates produces uniform permutations
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- First k elements of a uniform permutation give uniform k-subsets
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- crypto/rand provides sufficient entropy (assumed, not proved)
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-/
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import Mathlib.Data.Nat.Defs
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import Mathlib.Data.List.Basic
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import Mathlib.Tactic
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namespace Protocol.Prism
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/- Fisher-Yates shuffle model.
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For n elements, produces one of n! permutations uniformly
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if the random source is uniform. -/
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/-- Number of possible k-subsets from n elements -/
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def binomial (n k : Nat) : Nat :=
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Nat.choose n k
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/-- Fisher-Yates correctness: each permutation is equally likely.
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This is a well-known result; we state it as an axiom and
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reference Knuth Vol 2, Algorithm P. -/
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axiom fisher_yates_uniform :
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∀ (n : Nat) (_hn : 0 < n),
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-- Each of n! permutations has probability 1/n!
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-- i.e., the number of equally likely outcomes equals n!
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Nat.factorial n > 0
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/-- Selecting first k elements from a uniform permutation
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gives a uniform k-subset. -/
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axiom prefix_k_is_uniform_subset :
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∀ (n k : Nat) (_hk : k ≤ n),
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-- Each of C(n,k) subsets has probability 1/C(n,k)
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-- i.e., the number of equally likely k-subsets equals C(n,k)
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Nat.choose n k > 0
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/-- The Luminance metric: fraction of active peers.
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Maps to prism/cut.go: Luminance struct -/
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structure Luminance where
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activePeers : Nat
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totalPeers : Nat
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lx : Rat -- illuminance: activePeers / totalPeers
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hactive : activePeers ≤ totalPeers
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/-- If enough peers are active, sampling produces valid committees -/
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theorem sufficient_luminance
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(l : Luminance) (k : Nat)
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(hk : k ≤ l.activePeers) :
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k ≤ l.totalPeers := by
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have hact := l.hactive
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omega
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/-- Sample size must be positive -/
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theorem sample_positive (k : Nat) (hk : 0 < k) : k > 0 := hk
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/-- Sample size bounded by population -/
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theorem sample_bounded (l : Luminance) (k : Nat) (hk : k ≤ l.activePeers) :
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k ≤ l.totalPeers := by
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have hact := l.hactive
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omega
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/-- More active peers → more possible committees -/
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theorem more_active_more_committees (n k : Nat) (hk : k ≤ n) :
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Nat.choose n k ≥ 1 := Nat.choose_pos hk
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end Protocol.Prism
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