Public-facing architecture description of the FoF post-gating system
specified in docs/fof-spec/. Sits between section 20 (Encryption) and
section 21 (Delete Propagation). All subsections marked badge-planned.
Covers the user-facing 4-level visibility model, V_me primitive,
bio-post HPKE distribution, dual-mode operation (public-body+FoF-
comments vs FoFClosed), CDN-level comment verification, bucketed
padding scheme, revocation/rotation/key-burn lifecycle, PQ-readiness,
and the five ship-able layers.
Visibility variants table updated with the new FoFClosed row.
Disambiguation note added at top of section 20a noting this "vouch"
is the cryptographic V_me primitive, distinct from the directory
vouches in section 27. Reciprocal disambiguation note added at top
of section 27 pointing the other direction.
TOC entry added.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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