The Daily Moon

Your daily (lunar) base where you will find all the lightning-related news outer space.

Rusty Russel | Connect the World

The ins and outs of Blockstream and BOLT12

This week, in Episode 18, we talk with Rusty, a Linux and Bitcoin developer and a Lightning OG from Blockstream! We owe a lot to this lead Lightning protocol developer!
Rusty started hacking C-lightning in August 2015 and wrote “Reaching The Ground with Lightning” in November that same year! He described how to do Lightning using only the coming Segwit proposal. With Blockstream they were the first Lightning implementation!
We talk about Blockstream Aqua, Jade, Blockstream Green and Blockstream AMP. 

And Rusty also covers all the advantages of Lightning Offers / BOLT12. Implementing BOLT12 will take some time but we already can philosophize what this will do for the adoption of Lightning and for all those merchants out there! Are you crazy about Lightning like Rusty and us? And do you like to follow all Lightning developments as closely as possible from a lead developer? Then don’t wait any longer and treat yourself to watch or listen to the full interview or start reading below! Enjoy!

Watch or listen to the full interview or start reading below! Enjoy!


Blockstream states on their website the release of its own implementation: “c-lightning” in February 2020. But we know that you released c-lightning v0.5 in October 2016. What was your role in it? Can you tell us more about that time?

Wait, what?  No, by October 2016 I’d released c-lightning v0.5, and used an indirect payment to Christian Decker to sell him a cat picture (for 0.1 testnet BTC).

We were the first lightning implementation; the spec process really kicked off in Milan in October; by that point there were three implementations in various stages, and we all had to adapt to the agreed specs (in our case, rewrite!).

What’s the idea behind the blockstream satellite?

It’s hard to censor because Bitcoin is naturally a broadcast system.

Whats the difference between Blockstream Aqua, Jade & Blockstream green? They are all wallets, you can also use Blockstream Jade & Green together.

Aqua was intended to be a lighter wallet; I’d ignore it in favor of Green.  Jade is our cheap off-the-shelf hardware wallet; the design is fully open source, and it’s like $45 USD.  You just reminded me to finally order one now they’re back in stock!

Is Blockstream green the most complete wallet at the moment on the market?

No, but it’s been around for a long time and is rock solid: I use it myself.  The non-custodial nature was unique at the time Blockstream bought it, and is still pretty unusual. Needs lightning support though 🙂

Blockstream AMP is an asset management platform that allows users to issue and manage assets such as stablecoins on the Liquid Network. Will oil, gold and other assets be implemented? Is this the start of DEFI on Bitcoin Network?

AMP is for registered securities: it’s an extra layer using multisig where the authorizer vets transactions.  You can issue assets normally of course.



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Lightning | Bolt12

You were the first Bitcoin developer to try implementing The Lightning Network during the summer of 2015. What did you exactly do at that moment?

I started hacking!  C-lightning 0.1 was in August 2015, which could open channels, do simple HTLCs.  The “deployable-lightning” paper called “Reaching The Ground with Lightning” was done in November, which described how to do lightning using only the coming segwit proposal. 

Developments in the Lightning Network and all tools around it are happening at an incredible speed! What’s the most necessary to develop to get more pre-coiners aboard? And what is being done to make it more user-friendly?

I think we need more ways people can earn sats.  That’s better than some weird fiat exchange, and with Lightning it’s finally feasible to pay out small amounts.

Most of our community members use LND at the moment. What’s the big difference between Acinq, Lnd & C-lightning ?

LND concentrated on great user docs, a turnkey system and general user adoption! 

ACINQ run the biggest node; their Phoenix wallet which is a delight to use and is probably my favorite decentralized wallet.

We have generally been content to push the specification forward and aim for a clean, solid implementation, with little attempt to market or gain user share. C-lightning is the most lightweight, and tends to have the most optional experimental features for all the pending spec enhancements.

My focus this year is on user adoption, starting with the coming release.  Lightning Labs are focussing now on proprietary service offerings and have dropped the ball on specification work, so we need to make sure that adoption of improvements doesn’t suffer, which means more users of c-lightning, Eclair and LDK


Not so long ago you posted a proposal for a new set of Lightning gossip messages. The goal is to maximize efficiency. Can you explain why this is so important and how it works?

Every node tells every other node about changes in the network.  That’s pretty inefficient, particularly when you first connect to a new node.  We have heuristics like only gossiping with some of our peers (3 for c-lightning) but too much of that makes the network less robust!  Fortunately, Pieter Wuille and others developed mini sketch, which is a clever way of encoding information so you can extract the differences; this can be used (and is, by Alex Myers who we recently hired) to make gossip really efficient.

At the moment it’s cheaper to send a big amount of sats onchain (layer 1), but do you think in the future we will see bigger amounts of sats moving on the Lightning Network ?

No, I expect Lightning fees will increase, and remain roughly proportional to amounts: there’ll always be a breakeven point. Perhaps more value, but maybe not more sats?

Does c-lightning also have a maximum of 27 hops route? We reached that limit while balancing a Ring of Fire with 65 Nodes.

Yes, it’s a protocol limit. But it used to be 20 until Christian introduced variable onion sizes!  27 is not too bad…

You worked on Bolt12/Lightning Offers. What are the biggest advantages when you compare it to Bolt11?

They’re a layer on top: they’re a static image, for a start.  They’re smaller, which helps the QR codes on old phone cameras. Still, they can contain much more information; from simple accounting things like a vendor field to complex things like weekly payments and fiat amounts.

We believe in a real use case for Lightning. Paying in sats for everyday stuff. The things merchants really need are the option for recurring payments and the possibility to refund. A customer needs to be able to have a payment proof.
Bolt12 provides a lot of solutions native within Lightning. What are the biggest obstacles that exist before Bolt12 will be broadly available and used?

OK, so this comes down to the spec process!  We need at least two independent implementations to work together before the spec can be final and we can start promoting it in the wild.  Then wallets need to implement it, which is a big ecosystem.  Of course you can enable it in c-lightning today, but support from other nodes is needed: it probably could be done as an add-on if they take too long, however.

We talked with Sevi of and learned what we also experience on a daily basis: The Lightning Network needs to be as fast as possible to compete with fiat money systems! Bolt12/Lightning Offers works as a two step system. Will this be a problem for the speed of the Lightning Network?

Not really: each hop in a payment takes 3 steps, but only two is needed for an offer to fetch an invoice. So it’s theoretically 60% slower, but in practice the fetching of the invoice also serves as a probe for what payment paths are available, so the actual payment attempt will take fewer retries.

How important is the Lightning Network for the existence of Bitcoin in the future?

Bitcoin will still exist; there’s a role for savings and big spending.  But Lightning makes it possible to spend efficiently without custodial risk introduced by “Bitcoin banks”.

Is the Lightning Network mature enough for mass adoption? 

If not, what needs to be improved? If so, are there things that you really want to see improved?

There is so much work to do!  We need to improve privacy, improve payment resilience, have more infrastructure for higher level operations like refunds, etc.

What is the latest thing you are working on, right now?

One of the most requested features: multiple channels to the same node….

Can you give some tips to Lightning users who just finished building their own node?

Yes!  A cool name is important 🙂

What is the biggest mistake you made related to lightning?

Technically?  Going fully duplex on the htlc interaction; it’s optimal, but way too complicated and has been a source of bugs and incompatibilities across all implementations.  I wanted to avoid it, but there were string advocates in Milan, so I designed the optimal protocol.

What was the most difficult experiment you did on/with lightning?

Hosting the second Lightning Summit in my hometown of Adelaide!


We have a lot of great developers in our community. If they want to start developing for Bitcoin/Lightning, where would you suggest they start?

Seriously, c-lightning.  It’s all about the plugins you can build; most of the interesting stuff happens there.  Building services on top of a c-lightning node is pretty easy, and getting easier.  Check out commando, one of my favorites: it lets you send your node commands through the lightning network itself!

Would you like to see a cold wallet integrated instead of the hot wallet we use at the moment for the onchain funds in a node. Do you think it is technically possible or do you have another solution in your mind?

You always need to be somewhat hot, but some signatures can be automated, so you don’t have to approve every single packet 🙂

Are there already merchants or public places (horeca) in Australia using LN ?

A few; these days “accepting Bitcoin” means “accepting Lightning”, so it’s not the painful experience it once was.

How can we participate with the Volcano Bonds? The bonds using the liquid network.

We will be doing technical parts of the bond infra, but I don’t know anything about the actual issuance.

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Picture of Ramon Korpel

Ramon Korpel

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