Every Bitcoin user is supposed to have their own full copy of a blockchain. Unfortunately, it takes more than 400 GB of storage and this number goes up every 10 minutes. Most smartphones and even laptops don’t have enough free space to store blockchain, which is a big problem. The first attempted solution is called SPV (BIP 37), short for Simple Payment Verification. SPV-enabled Bitcoin wallets aren’t required to store a full copy of blockchain, and they often need less than a few hundreds of megabytes.

SPV is not an ideal protocol, and it has some serious flaws. Even if it was flawless, having fewer copies of blockchain weakens the whole Bitcoin network. You should consider running your own full node if you’re in a position to do so. For other situations, it’s nice to have a way of using Bitcoin without setting up a full node. Being able to install a Bitcoin wallet by a single tap on your phone screen certainly helps the adoption.

I’ve been playing with RaspiBlitz recently, mostly because I wanted to evaluate the current state of Lightning Network. It’s been a pleasure, so far, but it requires some technical know-how, and you also need a few hundred dollars worth of hardware in order to bring up a node. This doesn’t look like something with an explosive potential for mass adoption, which led me to the following question: is it possible to have a Lightning wallet without having a full node? I’d love to have such an app on my phone.

It turned up, there are a few ways to run a Lightning wallet without having a full copy of Blockchain. The most interesting one is called Neutrino, or BIP 157 / BIP 158. It can also be used by Bitcoin wallets, and it’s supposed to replace SPV. This means that we can totally have a reasonably secure and private Lightning wallets in the form of simple mobile apps with no extra costs or manual setup. Looks like the future of Lightning Network is bright.