Watchtowers

A Lightning channel partner can cheat by broadcasting an old commitment tx. To detect and revert, the honest party must broadcast a "justice tx" within to_self_delay blocks. Watchtowers do this monitoring on your behalf when you're offline.

Threat model

Watchtower is untrusted for fund custody. It only learns:

• Channel txid (from txid_prefix you provide).
• Encrypted blob (the justice tx).

It does NOT learn:

• Channel balance.
• Counterparty identity.
• Payment activity.