Electrum Wallet Founder Thomas Voegtin discussed in an interview during the Bitcoin Wednesday Amsterdam, the current state of Lightning Network integration in its wallet which used to account for 10% of all Bitcoin transactions at some point.

The initial proposal for the integration started one and a half year ago, discussing the design and compononents needed to integrate Lightning:

One options would be to have the following setup:

• Normal ElectrumX
• Electrum Lightning Hub, based on an existing Lightning implementation, but supporting a new protocol for talking with the Electrum Client
• Transaction watcher would gain the capability to watch for send breach remedy transactions
• A btcd instance would be needed in addition if lnd is used

The Electrum Client would not need to do Lightning routing, since it would always talk directly to the Lightning Hub over a custom protocol. Maybe the hub could be implemented as talking to something like lncli, so that it wouldn’t be necessary to fork.

The Electrum Client would be an independent Lightning node, so the server would need to hold money but users should fund their own channels with the server. So a client would only be able to receive after opening a channel itself.

Although the developers are running security tests to ensure high level of safety for users, deterministic wallet recovery using seeds will not be possible since the transactions will be offchain. This is a particularity of lightning channels and not Electrum wallet itself. Users will still be able to restore “Bitcoin” keys using the seed as before, however, they will not be able to recover lightning channels from the seed. It means any bitcoin that was locked in channels will be lost if not backed up properly beforehand. The Electrum developers aim to address this issue by including a backup service which will save an “encrypted” backup of lightning channels where the user is trusted to not loose.

The integration has already started and the developers can “already send and receive Bitcoin on the lightning network” although this is currently done on the Testnet to ensure it is fully safe before making it available for users on Mainnet.

A Watchtower service within Electrum is also underway because it is a basic requirement for Lighning Networks that the channels be watched at all times. Furthermore, “tech savy” users will be able to use the Watchtower component to deploy their own watchtowers.

On the UI/API side, the design is made such that it will resemble the original Electrum wallet focusing on usability while feeling familiar for existing users. It is intended to have the usual “send and receive screens” although the mode of operation will be different. Users also don’t have to interact with the Lightning Network all the time.

Release is scheduled for the end of 2018 although it may go beyond that.