- Identity announcements: verify Ed25519 key validity and X25519 consistency - Envelope signatures: verify Ed25519 signatures on signed messages, drop invalid - Block header validation: height range, hash length, timestamp sanity checks - TX relay validation: hex validity, size bounds, version check before broadcast - Rate limiter struct for per-peer relay operations - Message sequence number field (seq) added to TypedEnvelope for ordering Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>