RELAY_PROOF previously had no per-envelope dedup — every relay that
saw the gossipsub re-broadcast could extract the sender's FeeSig from
the envelope and submit its own RELAY_PROOF claim with its own
RelayPubKey. The tx-ID uniqueness check didn't help because tx.ID =
sha256(relayPubKey||envelopeID)[:16], which is unique per (relay,
envelope) pair. A malicious mesh of N relays could drain N× the fee
from the sender's balance for a single message.
Fix: record prefixRelayProof:<envelopeID> on first successful apply
and reject subsequent claims for the same envelope.
CONTACT_REQUEST previously overwrote any prior record (including a
blocked one) back to pending, letting spammers unblock themselves by
paying another MinContactFee. Now the handler reads the existing
record first and rejects the tx with "recipient has blocked sender"
when prev.Status == ContactBlocked. Block becomes sticky.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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