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chains/schain
zeekay 6552bd69cd schain: Stage 2 — cryptographically verifiable signed pinned-writer (deletes raft's serialized writer)
The Stage-1 allocate gate was owner-gated in LOGIC (pinning.IsOwner over the
block's threaded proposer) but UNENFORCEABLE by a verifying node: a Lux block
carries no verifiable proposer, and resolving one (GetValidatorSet) can be a
network call, so the gate could not run inside the pure, local block apply. The
chain was therefore unsafe for >1 validator.

Make ownership self-attested and cryptographically verifiable:

- AllocateTx gains Signer/SignerScheme/SignerPubKey/Sig + Epoch/Nonce/Fingerprint.
  Sig is an ML-DSA signature (FIPS 204, the SAME scheme the validator NodeID
  derives from) over the SP 800-185-framed bytes Range|Count|Epoch|Nonce|
  Fingerprint. The owning proposer signs at BuildBlock with its staking key.

- Verify (applyAllocate) is pure + local: recompute owner = pinning.Owner(R,
  V@epoch); require Signer == owner; re-derive the NodeID from the carried public
  key (ids.DeriveMLDSA — the NodeID is a SHAKE256-384 commitment to the key) and
  require it to equal Signer; ML-DSA-verify the signature. Any failure rejects the
  whole block (fail closed).

- Validator-set locality: GetValidatorOutput carries no ML-DSA key, so Verify
  binds the key via the NodeID commitment instead of a set lookup, and uses the
  EpochFingerprint carried in the tx (recomputed from the local snapshot) as the
  DESIGN 6.4 guard — the network call (set resolution) happens in BuildBlock,
  never in Verify.

A non-owner's forged allocate is unverifiable by construction: it cannot sign as
the owner (no key), and claiming the owner's NodeID with a foreign key fails the
re-derivation. This is the property that replaces raft's serialized writer.

Tests (real ML-DSA keys, production NodeID derivation, no bypass): owner-signed
accepted + contiguous/monotonic; non-owner-with-VALID-key rejected; forged sig
rejected; foreign-key-for-owner-NodeID rejected; tampered tx rejected; epoch and
fingerprint mismatch rejected; verifier accepts owner-signed block regardless of
relay; state-root/manifest tests stay green. Full schain suite green under -race.
2026-06-25 15:47:37 -07:00
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