ltl-accumulator-verified/README.md
mrwulf be232507cc S4: descent extractor extractMTH (Theorem 3 step 3 + F2 restoration), non-vacuous
The 'descend' step of the paper's Theorem 3, built extractor-first per
the S3.5 lesson (never a bare '∨ collision'):

- extractMTH (D D'): total function that, given two equal-length leaf
  lists sharing a Merkle root, walks the common-shape tree to the first
  divergence and returns the concrete colliding preimage pair (a node
  pair, or a leaf pair at the bottom).
- extractMTH_correct: |D|=|D'| ∧ D≠D' ∧ MTH D = MTH D' →
  IsCollision (extractMTH D D'). Proven by functional induction on
  extractMTH; composite case uses MTH_split + append_inj (fixed-width
  Hash) to split node preimages or exhibit the node collision.
- extractMTH_nonvacuous: equal lists → output NOT a collision (pinned),
  so the conclusion is false for some inputs ⇒ choice-proof.

This also RESTORES, in explicit non-vacuous form, the receipt-uniqueness
content of Lemma 2 deleted in the S3.5 cleanup (re-audit F2): the honest
Merkle fold is injective up to a collision.

18 certs green. Fable statement-audit passed (matches paper Thm 3 step 3
verbatim). LTL untouched (12 leaves, bcd15f9d).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-07-11 16:46:58 +02:00

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# ltl-accumulator-verified
Lean 4 mechanization of the security analysis (§6) of the paper
"The Lean Transparency Log" (https://ltl.zkdefi.org/paper): the Merkle
accumulator's own correctness and soundness theorems, kernel-checked, in
the same discipline as the four `*-ed25519-verified` subject corpora.
## Status: layer scaffold (work in progress — honest ledger below)
| layer | content | status |
|---|---|---|
| L1 | bytes, hleaf/hnode, domain separation (Lemma 1) | **done** (domsep: axiom-free) |
| L2 | MTH, Root, ConsRec definitions + termination | **done** (cones: propext, LTLAcc.sha256, Quot.sound) |
| L3 | inclusion completeness (Theorem 1) | **done** (incl_complete: propext, Classical.choice, LTLAcc.sha256, Quot.sound) |
| L4 | frontier binding content (Lemma 2) | **inlined in the extractor walk** (extractIncl); standalone receipt-uniqueness theorem queued for S4 restoration in extractor form |
| L5 | inclusion soundness = EXPLICIT extractor `extractIncl` (Theorem 2) **done, non-vacuous** |
| L6a | descent extractor `extractMTH` (Theorem 3 step 3; restored receipt-uniqueness of Lemma 2) **done, non-vacuous** |
| L6b | ConsRec binding + Theorem 3 assembly (extractCons) | pending (S5) |
| L6 | pin-store state machine safety (Proposition 1) | pending |
## Discipline (identical to the subject corpora)
- `verification/Proofs/` contains ZERO `axiom` declarations; the single
sanctioned axiom site is `verification/gen/` — here, one opaque
function: SHA-256. The theorems are constructive collision extractors,
so collision resistance is never assumed, only interpreted.
- `verification/check.sh` is THE button: compiles every file through
`lean-guard` (memory cap, core pinning, timeout, single-flight lock)
and axiom-audits every certificate against its documented exact cone.
- Expected boundary: `propext, Classical.choice, Quot.sound` plus
`LTLAcc.sha256` for hash-touching certificates — documented per
certificate in `check.sh`, audited both directions.
The finished certificates are destined for the LTL itself as attestation
leaves: the log carrying kernel-checked proofs of its own machinery.