Identity escrow wraps {tunnel_token,pbs_token} under the SAME R via age
(scrypt+ChaCha20-Poly1305), reusing the K-escrow pty; wrong R fails closed.
escrow.Create optionally emits the identity blob; escrow-create uploads it +
the non-secret directive; identity-consume recovers it (R by hand, never
logged). K-escrow + 10C Consume untouched. Closes slice 10 with hub v0.11.0;
operator-side rotation model (hub holds no Cloudflare write-power).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
internal/escrow: zero-knowledge escrow creation. R = 10 EFF-wordlist words
(crypto/rand, ~129 bits); wrap K under R via PBS-native key change-passphrase
driven over a stdlib pty (x/sys/unix; output discarded so R can't leak, F-A2);
self-verify the blob recovers K (fingerprint match) before shipping. Opt-in (b)
R-wrapped offline copy + (a) raw paperkey. Live K is byte-unchanged (operates on
a copy). --selftest=escrow-create (-storage/-paperkey/-offline/-upload). Posture
config field (zero_knowledge default). PBSEncKeyPath helper. Grounded by the
escrow spike findings.
Tests: R entropy>=128/format/uniqueness; integration round-trip (wrap->unwrap
fingerprint match, wrong-R fails, K byte-unchanged) guarded to linux+pbc.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>