Bitcoin and many other cryptocurrencies suffer from scalability issues. Payment Channel Networks (PCNs) are the most prominent approach to overcome these issues. The main idea is to reduce the transactions on the blockchain by establishing payment channels between users and allowing any two users connected via a path of channels to perform payments. PCN are already deployed in practice, e.g., the Lightning Network currently has 80k channels, 30k users and 200M USD locked. However, the current state-of-the-art in PCNs (i) is limited to payments, (ii) has security issues (i.e., wormhole attacks), (iii) is costly (i.e., funds are locked for a time proportional to the payment path length), (iv) is inefficient (i.e., it takes two rounds to complete payments) and (v) has a dependency on specific scripting language functionality (e.g., hash time lock contracts).

In this talk, I will show some recent protocols that overcome some of these challenges. I first present Blitz, a new multi-hop payment scheme that aims to improve on security and efficiency. Second, I present Donner, a Virtual Channel scheme that allows to connect any 2 endpoints in a PCN for the purpose of direct payments. Finally, I would shortly overview some of the open challenges in this setting.