dav1d returned the §3.4 φ_PRG anchor-map review with a decision set:
HMAC-SHA-512 / 32-byte seed / uint32-be counter from 0 / SHALL-replace
all LOCKED; manifest field renamed; float-map prose corrected; two
ADDs (exhaustion guard + seed-independence rule); M1-policy separation.
Spec text (#000035 §3.4):
- Folded dav1d's full corrected §9.10 wording (RESPONSE_1 §1).
- Manifest field phi_prg_seed → anchor_prg_seed (purpose-scoped, not
implementation-scoped; phi_prg_seed kept only as a code-local alias;
phi_seed / m1_anchor_seed rejected as too vague / too policy-tied).
- Float map 2·(u32/2^32)−1 unchanged (KAT compat) but the prose now
says "uniform over a 2^32-point grid in [-1, 1) with negligible
finite-grid mean −2^−32" — NOT "unbiased". -1.0 reachable, +1.0
not. If exact zero-mean is ever needed → midpoint map x =
2·((u32+0.5)/2^32)−1 with a PHI_PRG_VERSION bump + new KATs, never
a silent change.
- Added dim_h ≤ 16·2^32 exhaustion guard (4-byte counter ceiling).
- Added seed-independence + single-purpose-seed requirements (seed
must be generated independently of model/data, not adversary-
selected, not reused for other PRG domains — no domain-separation
tag in v1).
- Added §9.10.1: M1 enablement is a mitigation-selection-policy
decision (e.g. skippable under #000034 NO_ALIGNMENT), not a §9.10
function-definition question; "MUST NOT claim M1 while still using
embed_hard_to_vec" prevents fake-M1 deployments.
- Added an endianness-confirmation note: big-endian is pinned to the
impl + KATs; flip only if v7 TLV convention turns out little-endian
(would need a PHI_PRG_VERSION bump).
- SHALL-replace wording kept (RFC-2119 strong mandate inside M1).
Implementation (arborist/substrate/anchor_prg.py):
- New dim_h > 16·2^32 → ValueError guard (clean message naming the
ceiling rather than overflowing the counter deep in _expand).
- bool dim_h now rejected explicitly (isinstance(True, int) is True).
- Module + function docstrings updated: manifest field is
anchor_prg_seed; seed-independence / single-purpose rules; corrected
float-map distribution wording (negligible mean −2^−32, not exactly
zero); endianness note.
Tests (tests/test_anchor_prg.py, 27 → 30):
- test_phi_prg_rejects_bool_dim_h (True/False params).
- test_phi_prg_rejects_dim_h_above_counter_ceiling.
Doc cross-refs: soft-hash-channel-analysis.md §9.2 + §11 status note
the dav1d-reviewed §9.10 wording + anchor_prg_seed field name.
#000035 ticket status + TICKETS.md row updated. AUTOCOUNT markers
for test_anchor_prg.py bumped 27 → 30 across 5 doc files.
Full suite: 2291 passed, 28 skipped.
russell@unturf.com
e894634406