Fully Discover the Balance of Lightning Network Payment Channels.

The Lightning Network is a payment channel network that runs on top of Bitcoin. It is an open network, in which anyone with a computing device capable of connecting to the Internet can participate. Every participant is referred as a node. The direct link between two nodes is called a payment channel. Two nodes connected by the payment channel can conduct transactions, even in parallel. If two nodes without connecting directly a payment channel want to trade, the sender needs to start the route discovery algorithm to find a payment path connecting the sender and the receiver. The route discovery algorithm is based on the channel capacity, and the ip address of the node is public. To protect the privacy of users, the specific distribution of balances in the channel is confidential. The channel capacity is public and has been determined at the beginning of the channel establishment. The balance is private and has been dynamically changing, which brings challenges to the routing discovery algorithm. A channel balance disclosure attack was proposed to reveal the channel balance of most channels in the network. In this paper, we propose an enhanced channel balance disclosure attack that can reveal the balance of any channel in the network. We utilize a payment channel that can contain multiple outstanding parallel transactions at the same time to break the limit of the maximum value of a single transaction, thereby revealing the user’s precise balance. We explore countermeasures against enhanced balance disclosure attacks.