Gossip ingestion validation is incomplete (I-002)

[branarakic]

Migrated from dkg-v9 issue #73

Context

Feedback item I-002 — Severity: High

What has improved

• Gossip handling moved to dedicated GossipPublishHandler class
• Structural validation via validatePublishRequest() added
• Data stored as tentative first — old heuristic that trusted self-reported startKAId/publisherAddress is gone
• When gossip includes txHash + blockNumber, targeted on-chain verification promotes to confirmed

What remains

• Gossip messages themselves are not cryptographically signed
• No merkle verification of the gossip payload against claimed roots
• A malicious peer can broadcast structurally valid but fabricated data that will persist as tentative
• No signed ack on gossip path

Recommendation

Add publisher signature verification to gossip messages so receivers can reject unsigned or misattributed broadcasts before storing.

Evidence

• packages/agent/src/gossip-publish-handler.ts:115-199 (current validation)
• packages/agent/src/gossip-publish-handler.ts:187-189 (tentative-first)