A Timeout Anonymous Payment Channel for Decentralized Currencies

Anonymous payment channel (APC) was introduced by Green and Miers (CCS’17) with the Bolt protocol. This work contributes with the growing body of work on off-chain channels aiming to enhance the scalability of cryptocurrencies in the number of (in this case, anonymous) transactions per second. Although Bolt presents a secure formulation, we observe that it requires cooperation between costumer/merchant, the protocol players, in order to complete the protocol. More concretely, in its current form, if the costumer does not cooperate, the protocol cannot complete. The reason is that the costumer is required to start the channel closing procedure and it is not clear what happens if it does not. In this work we address this problematic situation with a variant definition for APC, which takes into account a timeout parameter, and present a protocol construction.