Pitfalls

Overview

This document describes some exploits/pitfalls which the lightning-signer must mitigate.

• Shared Allowlist

Fee calculation when signer invoked multiple times

• Real inputs: 2 + 2 BTC
• Malory wants to sign a tx with output 3.
• Malory asks signer to sign tx with inputs 2 + 1 and then with inputs 1 + 2, where the signer signs the 2 input each time
• Signer thinks total is 3 each time, but it's actually 4
• 1 BTC is burned as fees

Taproot fixes this (signs all input values at once).