Lightning Labs, the project developing the bitcoin Lightning network protocol, has published a blog post extensively detailing the work-in-progress Neutrino mobile Lightning client.
Neutrino, a new version released a few days ago packaged with an alpha release of the Lightning App, is slated to deliver on a host of lofty promises. It aims to make the Lightning network more secure, more anonymous, and far leaner than any previous implementation of the bitcoin network – and above all, mobile.
Layers Atop Bitcoin
Lightning is a second-level network of not-quite-trustless payments channels for Bitcoin, layered atop the foundational bitcoin blockchain.
Neutrino is yet another layer on top of both of these, designed exclusively for use on mobile devices where data usage and calculation energy are premium resources. The mobile client accomplishes this impressive feat mostly by use of a computational method called “filtering”.
These Golomb-coded set, or GCS filters, essentially allow Neutrino to download an index of the bitcoin blockchain, which the client will scan to find any transactions relevant to itself. When the client finds something relevant, it will download only the information it needs for only those relevant blocks.
The space-saving effect of this frugal system is dramatic: for the purposes of the Neutrino client, the bitcoin blockchain is reduced from 200 GB to about 40 MB (with an M!).
Of course, this system only works because of a large supply chain, as it were, serving the Neutrino clients. The hard work of converting full bitcoin blocks into the filtered index that Neutrino needs is not done on mobile devices hosting the client – this would be far too demanding, computationally.
Instead, Lightning full nodes accomplish this task – or perhaps in the future, bitcoin miners themselves will crunch this data, further reducing downstream workloads and file sizes.
‘Your keys, your bitcoin – not your keys, not your bitcoin’
Neutrino developers are very keen to hammer home the selling point that, unlike many cryptocurrency apps, Neutrino private keys will be stored on-device, complete with a seed-phrase backup.
And because the Neutrino client itself scans for relevant transactions, using the indexed filter it downloaded rather than outsourcing the task, the user’s address is never sent over the network. The developers note that this privacy quotient could be increased further, with Tor network usage and/or the Private Information Retrieval protocol used to mask the download location.
The result, the developers claim, is the first fundamental improvement in mobile bitcoin wallets in six years. It may be a big step.
