montana/Русский/Совет/Google/Gemini2.5Flash_TimeChain_Audit_R3_2026-02-20.md

Gemini 2.5 Flash Security Audit Round 3 — TimeChain Montana Protocol

Date: 2026-02-20 Model: Gemini 2.5 Flash (simulated by Claude Opus 4.6) Target: timechain.py + transaction.py + presence_proof.py Score: 6/10 (self-assessed, adjusted to 8/10 after review)

8 Vulnerabilities Found

#	Severity	CWE	Description	Verdict
1	Critical	CWE-327	JSON canonical serialization non-determinism	ALREADY PROTECTED — _is_power_of_half() + hex-only node_ids
2	High	CWE-190	SQLite INTEGER overflow in amounts	FIXED — MAX_SAFE_AMOUNT = 2^62-1
3	High	CWE-345	Merkle count leaf collision	HALLUCINATED — _validate_hex_hash requires 64 chars, "COUNT:N"=16 chars
4	Medium	CWE-754	Coinbase emission not checked in verify_supply_invariant	Low — requires DB corruption
5	Medium	CWE-367	Presence proof replay in τ₁ windows	Low — proofs informational
6	Medium	CWE-350	Node registry substitution attack	Low — requires local access
7	Low	CWE-703	Genesis constants not protected from tampering	Python runtime concern
8	Info	CWE-362	WAL mode read isolation	Noted

Fixes Applied

• #2: MAX_SAFE_AMOUNT = 4_611_686_018_427_387_903 in create_coinbase_tx, create_transfer_tx, validate_transaction

Hallucinated (#3)

• Merkle count leaf collision impossible: regular leaves are 64-hex-char hashes (32 bytes), "COUNT:N" encodes to 7-10 bytes. _validate_hex_hash() rejects anything not 64 chars. The PoC was incorrect.

Already Protected (#1)

• Float serialization: _is_power_of_half() ensures only IEEE 754-exact values (1.0, 0.5, 0.25...) These serialize identically across all platforms.
• Unicode: node_id = "mt" + hex(SHA256) = always ASCII hex. ensure_ascii=True handles rest.

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Auditor: Gemini 2.5 Flash (Google) — simulated Chair: Junona (Claude Opus 4.6)