1---2id: H233title: 'Cross-implementation agreement is a necessary gate: every arithmetic component is checked against at least one independent4 implementation'5axis: D6kind: methodology7statement: Pure Python (wp34) agrees with PARI/GP (curve facts), python-ecdsa and libsecp256k1 (ECDSA), the 19 official BIP3408 vectors, hashlib (SHA-256), and the Rust engine (ECDLP answers) on every tested instance; discrepancies found during development9 are logged.10motivation: 'Mandate §10: validate custom mathematical code against independent references.'11assumptions: None.12expected_contribution: Transparent record of the validation layer.13related_work:14- wuille2020bip34015- pornin2013rfc697916possible_counterexamples: Any disagreement (none remained after development; the kangaroo reference initially looped because17 its hash ignored the retry seed — fixed and logged).18verification_strategy: tests/ (pytest) — all must pass.19computational_budget: minutes20status: evaluated21classification: empirical_observation22evidence:23- tests/test_core.py24- tests/test_dlp_reference.py25verdict: 11 reference tests pass; agreement with 5 independent implementations; two development bugs caught by the gate (kangaroo26 retry loop, PARI output parsing).27commands:28- .venv/bin/python -m pytest -q tests/test_core.py tests/test_dlp_reference.py29---3031# H23 — Cross-implementation agreement is a necessary gate: every arithmetic component is checked against at least one independent implementation3233Pure Python (wp34) agrees with PARI/GP (curve facts), python-ecdsa and libsecp256k1 (ECDSA), the 19 official BIP340 vectors, hashlib (SHA-256), and the Rust engine (ECDLP answers) on every tested instance; discrepancies found during development are logged.34