Extrinsic signing no longer goes through ExtrinsicPayload.sign(pair). That helper
calls pair.sign(encoded, { withType: true }) and has nowhere to put a signing
context — and an ML-DSA pair refuses to sign without one, so before this the
extension simply threw.
The two lines it would have run are reproduced here with the context added:
encode the payload, BLAKE2b-256 it if it exceeds 256 bytes (Substrate's own rule
from unchecked_extrinsic.rs, which signer and runtime must apply identically),
then sign. Forking @polkadot/types to thread an option through was the
alternative, and is a far larger commitment for the same result.
The context comes from the payload's specVersion, because that is the only place
it can come from: spec >= 148 verifies under QUANTUS_EXTRINSIC, earlier specs
under the empty context, and only the caller knows which runtime it is talking
to. Getting it wrong produces a signature that is cryptographically valid,
rejected by the chain, and indistinguishable from a correct one without asking a
node — which is why both directions are pinned by tests rather than assumed.
Raw bytes use the **empty** context, deliberately not the extrinsic one. A
signature made for a dapp login must never be replayable as a transfer, and the
context is bound into the signature itself. u8aWrapBytes stays, but it is not
what provides that guarantee — it is polkadot-js's own <Bytes> wrapping, kept so
a verifier written against that convention still sees what it expects. For ML-DSA
the context is authoritative: it cannot be stripped or forgotten by a verifier
the way an in-band wrapper can.
No Quantus-specific bytes context is invented. Nothing else in the ecosystem
defines one — the chain and the SDK name only QUANTUS_EXTRINSIC — and making one
up would produce signatures no other Quantus tool could verify.
Raw signing returns sig||pk, which is not a convenience: the account id is a
one-way Poseidon2 hash of the public key, so a verifier holding only an address
cannot recover the key. The key has to travel with the signature. Pinned by a
test that verifies against the signer's address and nothing else.
79 tests pass; typecheck, lint and build:chrome clean.
Refs quantus/extension#4, quantus/common#5
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012uDUodEcRbBwNRi3UCmw8f
7fa26252f0
