Expanding Bitcoin’s Global Reach Using Lightning with Rusty Russell – Blockstream Talk #33

Welcome back to blockstream talk today We're speaking with Rusty Russell about The lightning Network Rusty is one of my Favorite guys to talk to and we had a Lot of fun in this conversation we Covered a lot of ground including my Recent trip to El Salvador and some General observations about how the Lightning network is being used on the Ground in s Salvador we also covered Updates on green light and green Wallet's recent lightning integration as Always if you found the conversation Useful don't forget to like subscribe And Share Rusty welcome back to the podcast thank You it's good to be back on is this Number two or number three I think it's Number two is it number three wow okay Uh you spot there uh it's at least two Um I I get a feeling it should be three Is it you know we should do this more Regularly for not if it's not already up To three anyway yeah yeah definitely so I think you know we covered your Background and all of that in the Previous podcast but I think maybe just For anyone who might be new we might Want to go through that again so can you Share a bit about your background and What your role is at uh blog stream sure Um I'm an open source developer for the Last like 25 years um that's been like

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My full-time gig uh people keep paying Me to write code that I give away which Is kind of you know at the time I Started was you would not have convinced Me that that was going to happen but um You know uh basically at the end of the Day people people want the tech right And so um know about uh eight almost Nine years ago now I uh um I joined Blockstream um and part of that was was Basically to work on Lightning which at The time didn't exist it was it was on Paper uh no one was really going to Implement it um and I was like okay cool Well this seems like a cool thing to do Um let's let's go and try to try to make An implementation um and that fed Through into the spec process and you Know um and everything that has happened Since then so that's that's kind of my Background I've always been an open Source coder uh and I guess and I am the I think the Most most senior or like longest longest Serving blockstream engineer at the Company uh so I guess that's my other Other claim to fame very very nice oh so You mentioned the the implementations For lightning so how do you there's Multiple implementations so maybe you Could run us through quickly what the Main implementations are and then how do You guys work together developing Lightning Network across all of those

Implementations right okay so there's Sort of four main ones um there's um Lighting Labs have L&D there's uh uh Async have eair and Phoenix uh their Mobile Wallet um we have core lightning Of course uh from blockstream and there Is um uh LDK from what used to be called Square crypto is now called SP spal uh Those people um and that's more but That's more of a kind of a a Construction set of pieces uh so it's Kind of a different approach there uh Each of them in a completely different Programming language so there's kind of Something for everyone in there um but The way it works is there's a there's a Spec that basically we follow uh and That's kind of a negotiated spec on kind Of what we think we should do how we Should add features and things like that It's pretty carefully designed so that We can make progress so that we can uh Add new features make them optional Things like that so people can kind of Experiment but also we can go cool okay We want to migrate uh we found a better Way of doing it you know uh we want to Migrate the network across let's do it Stages so the result is a pretty smooth Experience for users and sort of a Continuous continuous Improvement both In implementations and in the specs that They follow so it's you know we have Bi-weekly meetings um and every so often

Every 12 18 months there's like a Face-to-face Gathering somewhere of all Contributors from all the teams and we Kind of get together and hash things out And that's always a a pile of fun um to To just you know to kind of geek out Over the details on these things um that That users won't really care about but It's really important to get right um When when your real money's on the line Which users do care about they do care About that's right they care about when It doesn't work right that's right and Fun fact about aair I just learned from You that aair actually means lightning In French that's right so apparently the The theair pastry kind of that people Think of is basically because that's That kind of whipped cream supposed to Look like a lightning bolt apparently so I'm I'm a Western Canadian so I know no French but I do speak Chinese okay Perfect That's right so as the leading Contributor to the open source core Lightning implementation can you share Some thoughts on your development Philosophy for for me robustness is Incredibly important um you're trying to Add new features but at the same time You were trying to continually keep Ahead of the changes that involves you Know redoing your internals trying to Keep everything kind of tight um and

That's all that's that's a trade-off it Takes like years of experience um Sometimes you just have to stop Everything and kind of rework something Because over time things have built up And changed and you're like okay this is No longer fit for purpose we need to Redo this and that's always a bit of a Juggle um I feel that you know Um the job of an experienced engineer is To be the people who break things right You're the ones who have to go and go Right okay no this has all got to be Redone right um whereas that's that's Classic a classic way to tarpet yourself If you're not a senior Dev so that's Generally the way I work um I'm very Open very collaborative that's that's Been most of my career in open source so You know uh a bunch of people post at Stuff you can follow along all the Gory Details on GitHub we also have a Community call every second week on the Alternate weeks when the spec call isn't Pretty much um we have the cor lightting Community call um and people can drop in There and and talk about what they're Working on and and and things like that That's that's always a great to see move Fast and break things is not an Appropriate Philosophy for financial Technology no so that's this is this is Very much uh you know it's it's got to Work first and foremost um you know we

Have for example uh when we deprecate Something in Coral lightning um we have Traditionally given two full releases we Have release every three months so you Know you'll get six months before it Actually gets removed you get a a Warning we're actually backing off on That and making it even even slower the Next release or the release after we'll Have a new deprecation mechanism so Basically we will introduce the new Thing we won't deprecate the old thing We will give two releases then we'll Deprecate the old thing and then you'll Get two more releases then you get one Release where you can basically go no no No I still really need this and you'll Still be able to enable it manually um As a bit of a shut across the mouth kind Of it is going away in the next release But you know if you really need it you Can you can enable it for one one last Time um but generally we just try not to Churn too much um but inevitably you Know there are changes in the way the Network works and you're like well okay This is no longer really suitable and so You do have to to make changes but we Try very hard we are backwards Compatible since our 0.6 release which Is gosh I don't even know uh these days We use datebase releases so you can tell Uh you know the age of a release just by Looking at the number um but yeah we've

We've maintained compatibility since Then uh if you were running a node then As I was uh you can upgrade all the way To today uh without a hitch is that Maybe one of the key challenges for core Lightning development maintaining that Robustness and and and making progress At the same time absolutely so there's a Disproportion of work that goes on Behind the scenes to uh ensure backups Compatibility to make sure that we are Um that nose migrate smoothly uh between Releases and that you know that Everything's fit for purpose that we we You know we rework things that maybe we We took a shortcut in the first place Because that was fine you know fees go Up or something like that we need to get More robust um there's a lot of really Good feedback too from the spec process Because you're talking with other people Who are implementing completely Independently they go hey did you have This problem and you go oh yeah okay Here's how I solved it yeah but here's a Problem with that you know so there's a Lot of really good interaction between The teams uh because you know you're You're the handful of people in the World who are actually down in the you Know uh the bowels of this thing trying To trying to you know make it all work Um and that's actually incredibly Helpful too plus you know we generally

The other teams give really good bug Reports if there's a problem between two Implementations uh having someone on the Other side who can exactly tell exactly What's happening is is incredibly useful And I get I love those bug reports Because they usually like we do this This this and you do this and that's Wrong and here's the problem um and then Sometimes we debate we with spec says This we should do this but you know um a Lot of times um that that's that's Fantastic feedback you know uh to get so Yeah uh everyone's really really careful To make sure that things keep working And that you know it's it's a smooth Experience and we only add things after Now that said part of the balance right As you said like you kind of people want New features but also they want Incredible stability they never want Anything to change except things they Want to change um so we have a series of Experimental features uh this used to be You have to it used to be you had to do An experimental build now you can turn Them on individually at runtime you can Go cool okay I'm I'm I'm happy to test You know experimental implementation of Anchor or Channel upgrade or whatever Else goes in now that's a much more you Know if it breaks you get to keep two Pieces both pieces kind of deal um Obviously you know we we try to be

Robust with those but we don't guarantee Backwards compatibility um and it's it's An opportunity for us to test so that That lets us kind of split the Difference sometimes uh if there's some Work on the spec and we've got some you Know experimental spec changes we want We can turn that on in a limited way uh And see how that goes so you know we do That quite regularly and and users who Who have taste for that can can turn Those on and and and you know and spend S their hearts content yeah so so some Of those experimental features would you Characterize those as some of the kind Of achievements of the last maybe 12 or 18 months or absolutely right um you Know they tend to go sometimes they're Just internal things but generally they Tend to be protocol changes spec Improvements that are being proposed That we want to test out in the wild and That's how we do it we we enable Experimental option so people can turn On and play with it I tend to turn all The things on on my Note um just why not Um but for other people you know they Can they can choose their own they they Can choose their own risk appetite uh For how that's working and that that Generally works really really well last Time you were on we talked about Lightning adoption I think you probably Have to be pretty happy about the

General trend of adoption I mean we've Had a lot of price volatility over the Last couple of years obviously but it's Just been up and to the right in terms Of adoption um so what are your thoughts On that oh absolutely look you know it's It it's it's a slow grind right uh It gets better more users come on um we Hit we hit new and fun problems you know We improve things more users come on we Go round and round and round again um You know that's it's great to see um It's fantastic this adoption you know Seeing people using it simply because They need you know they need it as a Solution right rather than origin It was Kind of a novelty thing kind oh this Will be cool one day we're really Getting to the point where people using It because it's it's it's a requirement So that's that's fantastic to see and You know uh I see no reason I that that won't Continue at some point perhaps even you Know hockey s stick upwards which will Be a bit a bit you know you're never Quite ready for for that but you know We're as ready as we can be I I was in El Salvador recently for adopting Bitcoin and I don't normally use Lightning very often so I you know find A wallet go in there and put a couple Hundred bucks on it and then and then Mess around with it buy everything that

I can um got a bunch of t-shirts that Don't Fit I was looking for shirts for the Kids and they're like oh my wife's like Why are you buying like adult shirts for Children But anyway in in 10 years they'll have a Lot of Bitcoin shirts um so it's kind of Plan ahead right low time preference Right um so you know when I was looking For a wallet you I wasn't really sure What would be the best wallet um you Know I thought of of green right away so Is there can you give us any lightning Updates on on on green green is uh block Streams kind of you know sleeper wallet We've had uh a Bitcoin wallet since Forever we actually bought uh the Company behind green back in wellow Years and years ago now like really in The early days of block stream because We really loved the way they were doing It so that green is a non-custodial Wallet right so um they control one one Key but you you know there that that Times out it degrades to like your Single control so it gives you the The Best of Both Worlds right they can do Two-factor authentication for thresholds All those kind of things that you want Um but at the end of the day there's no Custody of funds they don't have any Control over your funds they can't stop Them except for like a limited period of

Time um and that that we really wanted To take that model and apply it to Lightning right because we don't want to Look after you know we we don't want to Have your Bitcoin thank you so um we Spent a long time trying to think about How to do this to the standards that That we want and the answer to us was Green light the where we host the Infrastructure but the keys in the Control stay with the user right um and So that way uh one of the obvious things To do then was integrate that into green Which has the same philosophy and also Hey a modern wallet you really want your Onchain funds and your lightning wallet Together um and so that that culminated We know we had to develop Green Light Christian Decker uh did a fantastic job Kind of building that Tech out and Making that robust and then you know the Final step was to attach green uh so you Can download green turn on lightning and You're actually we're actually hosting a Node for you uh that um but you're still Holding the key so we're just doing you Know uh all the all the maintenance and Things for you and upgrading you um and And you are control in control of your Funds at all times so yeah um look that Is a fantastic um wallet option that I Expect to only keep getting better is That live now yeah it's live now um you Just need to I think you need to still

Need to go in and turn on um I'm on on Android but you know uh that's it's it's There right there's no no waight no Waiting anymore no no downloading beta And stuff it's it's it's in by default So okay great that's very cool um Another thing that I bought with Lightning was I met um Miss Universal Salvador and she said um would you like To buy face cream and I just I found it A bit odd that she would you know come Up to me and Austin do I need face cream So I did buy a CBD face moisturizer from Um Miss Universal Salvador with with Lightning so you are looking very fresh You know hey I gave I gave it to the Wife so she Said she said This hey anyway um and and see that that I think is really interesting because The ability to um so this this is one One of my arguments with lightning is That it's very symmetrical Network right Uh people think of credit cards and Things like that which are very Asymmetrical Network right anyone can You know anyone who has a credit card Can use it to pay but um most of us Can't accept credit cards very easily Right there's a whole infrastructure and There's whole companies built on the Making it easier to accept credit cards Lightning doesn't have that problem Right if you can it it's it's if you're

On the light nowhere you can receive Payments almost more easily than you can Send them so um so there's a whole Undiscovered kind of uh niche of of Users there who uh who who can go do That and I think that that's part of the Cool thing is that they don't have to Ask anyone's permission they just start Using it and it just works yeah what do You think about these NFC cards I think Those are kind of cool too like Naka There's a couple of companies that has Th have those and they were you know Selling them in Al Salvador and people Were using them for coffee and stuff Like that I think that's kind of a neat Thing because you don't have to pull out Your pH right you've just got a card Which is great yeah yeah absolutely um And I look forward to you know this is The kind of thing that when you've got An open standard and you've got an open Spec you start implementing and people Get excited about it they go off and They do these wild things that maybe you Didn't think of or you didn't have the They put experience in one area they're Like hey we could we can combine these Two um and that stuff is always Fantastic to watch yeah definitely and You know since your last appearance on On the podcast are you seeing a Difference in in the way that people are Using a lightning Network at all you

Know as adoption grows are people using It friendly yeah I I mean we're seeing a More professional kind of uh you know uh We're kind of doing that slow migration It's not it's not like chalk and cheese But there's very much the hobbyist end And then there's like kind of more the Professional end um inevitably Mainstream adoption means you end up With more more of the professional end And less of the hobbyist end but both of Them both of them are growing um just The mix is you know is definitely Evolving towards you know you know Lighting is my business right kind of Thing rather than just hey I'm running It because it's cool um or you know hey I wanted to I want to buy face cream in El Salvador so I Sol the lightning Wallet right there's there's more you Know uh we are seeing more kind of like Industrial adoption and driving things In that way which you know is is Fantastic that those users um discover I Love those users because one one one They they they're really invested right So they give they tend to be like you Know um they give you really good bug Reports if something goes wrong um they Give really good Fair feedback on you Know hey this this I really like this I Don't like this and things like that um But also they tend to hit scale problems First right so they tend to be hey we've

Got a no it's got like you know 10,000 Channels and and here's our problems um That most of us you know won't see in The short term at least so one of the Things that I noticed was different is I Remember a couple of years ago there was A top end on Lightning payments I think It was was it $400 or a couple hundred Doar right right so um we had um we had A restriction in the early days like Kind of training reels on the light Network where you could only have there Were two actually two restrictions one Is a 32bit uh number the amount of Millat you could send which at the time You start any was about 10 bucks and now It's like a lot more than that but um You know uh and there was also a maximum Total Channel size that you could have Which was a different number um so um The the so-called Wombo option uh which Basically uh turns both these off is Interestingly finally the default now in The upcoming lightning release so one of The things that we we finally kind of Took that off you had an option to turn On for a long time but now that option Does does nothing it's on by default um In fact there was a Dev option to turn It off but generally you can't turn it Off uh because if you have the funds you Can you can just spend them that's that Has become pretty uh ubiquitous Throughout the network and but it only

Really makes differ you know makes sense These days if you're doing recently Large transfers yeah that's that's Pretty cool I mean I saw a bunch of People paying for bigger ticket items Like you know like expensive dinners and And then on the platform Formerly Known His Twitter I saw a guy do a hotel Payment for like 13 or $1,400 which is Pretty cool so I mean that's a that's a Pretty chunky payment for for lightning Network isn't it I mean that's pretty Cool yeah and that's that's part of what We're seeing with the Professionalization right so people Running bigger nodes uh more volume and Things like that it does clear the road A little bit and you know make make you Know make make more lanes for the rest Of us when we do need to to to make Larger amounts so that trend is Definitely uh up and to the right as Well yeah that's very cool and what are Your thoughts on custodial versus Non-custodial I mean when I was looking For wallets um I ended up uh downloading Blink which I think you know it worked As advertised it's it's popular in all Salvador was great but um you know when When you sign up and you send your Bitcoin over and you know you didn't put In a seed and your or you didn't record Your seed you're um you kind of like Okay well there's there goes my Bitcoin

I guess it doesn't matter if it's a Couple hundred dollars you know you Don't really sweat it but look there's There's always going to be a uh you know Uh our our job I always feel is to make A non-custodial as competive and useful And fully featured as possible right um And this this is kind of the block Stream story like look at green right It's like how do we do a wallet where You can have something else sign off and So you can have restrictions on what you Can spend without giving over control of Your funds right um and there are clever Answers to this in a lot of times you Know it's green light is exactly the Same thing how do you not have to have a Home node and all those things that that You know your phone inter operates with Um but still keep keep the control of Your funds um so you know I I think There will always be a spectrum of some Extent right um so I you know and Sometimes it's easy just to go full Custodial right cool you just you just Give me all the money and I'll sort it Out right um that is kind of somewhat Lazy I think um and for the rest of us It's to try really our job is to try Really hard to make sure that the full Self- custodial uh experience is as Competitive if not more competitive um You know as you say I think down the the Low end that that's fine right whatever

Um you know if if it's if it's petty Cash um then I don't you know it's hard To get to work drop about um but if if You it's easy to slide into that option Where you don't have realistically you Know you need to have a PhD in computer Science in order to operate your own Node that's not going to you know that's Not open to most people right whereas You want somebody to go cool I started With a custodial wallet and but then you Know the amount started to get up there And I went well well now it's time for Me to Take Back Control now that said um The the non-custodial experiences are Getting pretty good these days um you Know but there there even there there Are compromises right if you use an LSP And you do a zeroc channel you're Generally there's some trust involved in You know that early stage before the Confirmation is involved right it's not Absolute and you know there are Definitely caveats around that but That's a reasonably comfortable you know So there might be an hour where Potentially you know you haven't Actually got the funds yet um I'm still Waiting um but you know it's it's it's At least limited so there there is a Spectrum of of I think of of custody and Things like that um but you know we're Still kind of exploring it and I think It's important to push as hard as

Possible to make sure that everyone can Custody their own funds and that's just Fundamentally better for the Bitcoin Ecosystem yeah I think so and I think You know people get excited about things Reminds me of the ETF right like the ETF Is exciting because it makes number go Up but at the same time it's you know It's antithetical to a lot of what Bitcoin is about is that you're supposed To be able to you know you don't Splitting off the economic benefits of Bitcoin like it's supposed to be the Economic benefits that pull you into it And you learn by doing and you take Custody of your own funds you take some Responsibility um and and uh yeah the ETF makes me kind of reminds me of that As well Perhaps Perhaps Perhaps the ETF Will get hacked and people will learn a Very hard lesson about you know not Their keys etc etc right um you know People ever learn that lesson I just Feel like that's I'm still waiting for My mount's money right so I I don't know I I cannot throw stones here yeah yeah That's funny well I mean to be fair back Then it was a lot harder to get your Hands on bitcoin right so I think that's Well to be fair I was literally trying To sell some at the time right so I just It was like a forced huddle right so I Can complain too much about the like 800 Bucks or whatever I did not get at the

Time uh well I still can but eventually In theory right I will probably I will Almost certainly come out ahead just for Fun what was the price you're looking to Sell at then was it like like 800 or 700 Or something or was it way lower it was Even less I think it was you know it was A handful of hundred it was like you Know was a couple of Bitcoin whatever um Now I'll get a small fraction of that Back in Bitcoin uh ideally presumably Hopefully eventually uh but you know Obviously economically like that was a Great Forest hotle um you'll get some Bch too Though Yeah yay yeah uh you know um I yeah That's right hey how about just round up The Bitcoin you can keep the bch that's Fine you can sleep easy knowing that Somewhere out there there's Auditors and Accountants and lawyers that are you Know enjoying a yacht that's right from The proceeds of this but but you know as I said I was literally trying to sell it I cannot complain too much about you Know uh the you know all all the things That happened along the way it was it's You know but yeah look I think those of Us who've been in the industry a while Have a healthy skepticism towards any Custodian but obviously the custodians Themselves it is so much in their Interest to present themselves as this

Polished you know uh not like a Cardboard fronted prop town which falls Over in the first Breeze which in Practice tends to be the way it works Right and you see this enough and you go And every every time right it's like oh Yeah no but the new ones the new Generation they're so much more Sophisticated than the old ones and Everything else and then something Happened actually no they were they were Just making it up too their security was One guy with a hard drive who you know Fell under a bus and now the Bitcoin had Gone or he fled to India whatever it was Right so you know we you see this movie There enough and you go no no I don't Believe that the new ones are the fully Professional these these people are not Going to steal your money um or steal or Lose right or send it to someone else Who gambles it away or all you know uh It's basically the same movie slight Variance so perhaps eventually people Will understand that custodians are a Risk and they are a a significant risk They're risk for you specifically and The risk in general um but you know we Are uh it it's It's we're not there because when you Can just print money to save things Right um your money isn't really at risk Right your bank goes under that's okay The government will at some point bail

It out there's guarantees right when You're dealing with hard assets this is Not a lesson that that many people have Had experiened with unless you've gone Through the Bitcoin thing um and that's Probably going to be something that's Going to take time to learn before People adjust to go if you really care You have to hold it yourself I mean Really decades because it's part of the Bitcoin adoption curve right there every Every cycle we pull in new people and Then they make you know the same Mistakes it feels like they make old Mistakes yeah absolutely look and and to Be fair right the Bitcoin journey I mean I always said to people you know wait me When bitcoin's 25 and I'll tell you Whether it's success or not and even That may be a bit soon because you know When you've got a project changing Something as fundamental as money right Uh which touches everyone and is is Poorly understood that ubiquitous right That's actually a massive social change Just by itself mean nothing else changes Right um you know and and most of us Only trust things that have been around You know you don't want to be the first On the boat right you want kind of it to Be pretty seaworthy and of you know been Around for a long time uh and that just Takes time right people you know it's Going to take a generation before you

Really get um people to be completely Comfortable with something and I expect The same thing with Bitcoin we're going To learn all these lessons and you know Um it's just yeah again you know it's a Long journey low time Preference definitely all right so we're You know it looks like price is getting Exciting again in Bitcoin we're touching Up around $40,000 it feels kind of like You know maybe like 2020 or 2016 20 Early 2017 kind of thing um and uh you Know main chain fees are starting to go Up again so what does lightning need to Do to adapt to that kind of situation There are a couple things that that we Did one thing that the last Fe Spike we Had really pushed is this idea of um Using anchor channels so um it used to Be enlightening you had to you know we Both agree on this transaction and Instead of going on chain we're just Holding it in case we need it um but we Had to decide what fees to do on that so We kind of you know what are fees going To be in a month or whenever I'm going To need this transaction you took a Number you doubled it kind of thing you Know and you hoped it was enough um That's bad because you're overc Committing on fees and as you know when Fees were di Minimus that was fine but As they started going up that starts to Really hurt should you need to use it so

We switched this case where you can Actually add fees afterwards it makes The transaction slightly bigger but you Can bring your own fees later um uh but That work wasn't complete because you Still have to have some fees because Your transaction itself has to get in The men pool so things get wild enough Then a transaction that doesn't even pay Enough won't even get a look in so Although the child that attached to it Will will cover the fee the way Bitcoin Works at the moment you sees the first One goes no I'm not going to even it's You know sorry you're you're you're not Even going to be in the first however Many megabytes 300 megabytes of Transaction whatever it is I'm just Going to drop you and then it sees the Second one goes well I don't even know What this is right so there's a thing Called package relay uh that's that's Being worked on in Bitcoin core where You basically send them along as a Package and then you can assess them go Oh well add it together this one and the Child that it depends on um or that that That that pays the Fe for it together That's definitely worth me you know Pushing through this you know basically It also means that in our original thing We just we pay zero fees PR it all goes In the child right so that is um a Bitcoin a Bitcoin thing that will help

Us be much more Dynamic with our fees You if if you need to use your emergency Transaction right that you're holding Because the peer did something bad or They went away whatever else then right Now you now you kind of now you can Decide how much is worth to you to close The channel um that's one thing um the Other thing is implementations are just Getting smarter with trying to avoid Force closes right it used to be in the Early days if the PE did anything wrong At all your solution was go on chain You're like I don't know what they said Go on chain right uh I think roast beef Was said you know the other side makes a Bad joke you're like right I'm going on Chain right because it was cheap right As that you know that pressure obviously Mounts now we're a lot more tolerant we Kind of give you give you a few goes Right to try to get things right um Before for will go on chain um and you Know obviously a lot more fee management Kind of well is this urgent or not now We look at htlcs time out what are they Worth uh at least in core lightning We'll look at it and we go huh okay so I've got like a 500 set htlc is it Really worth me going on chain for this We currently do uh by policy but when we Do we start going you know okay so if I Get it in six blocks i' I've got this Much at risk if I get it in 12 blocks

I've got this much at risk how what are The fees how much how much am I prepared To pay it's not worth me pushing into Six blocks because that's not you know I'm there's not that much funds at risk So so getting much more sophisticated About Channel management is about Closing is important but also opening Right um using single transaction we' We've long support the idea of a multif Fund Channel where you basically go open All these together and it produces one Transaction with the Dual funding Talking about experimental features um The protocol explicitly written so that You could be negotiating with multiple Independent parties to produce this Giant transaction that does everything At once uh it could be opens it could be Closes it could be all these things um And the other thing is of course Splicing where you can basically change Your channel on the Fly rather than have To open a second Channel or close this One and open this one um you can go Actually let's renegotiate this funding Transaction I want to put some funds in And the other side goes cool well I want To take some funds out or I want to put Some more funds in again you negotiate Between the two of you this new Transaction you put it on chain and this Happens while everything's still flowing Through so there's no stopping waiting

For confirmations and things you keep Using the old Channel until the new Channel basically gets confirmed and Then you you sub in atomically so you Know this is just engineering work and And uh and spec work that you know was Always going to come but becomes more Interesting when you're really trying to Optimize for onchain fees so we talked From the user perspective you know the Benefits of of green light if you're a Muppet like myself you you want it to be Uh You don't want to write you don't want To run a lightning node but you want to Have you don't want it to be custodial Either and you want to be able to use Lightning in your when you're in Al Sal Or buying you know when there's an Option to buy face cream from um a Beauty pageant contestant um so what Other in what other situations is green Light important and what are the main Use cases green light is you anywhere Anywhere you'd want a lightning node Right green light uh fits right in there Um it's much more programmatic so for Example people who want to have a have a Product like um you know maybe they have A game or something like that they want To have people access to real SATs then Um they can basically give out Greenlight nodes effectively to their Users right uh now there's original

Certific I think we allow you like a Thousand nodes before you have to come Talk to us and we'll figure out what Pricing is but you know um for the Moment in this phase we're just kind of Trying to encourage adoption and and and And you know and for us as core Lightning developers it gives us a great Insight into how people actually use Core lightning and you know rough Features things that we we we need to Work on so we get some really good Feedback um from just just having the Usage right so um at this point we're We're fairly fast and loose but anyone Who who basically wants lightning knowes Or importantly wants you know say you've Got a game or something rather than Having an ingame currency you go we're Just gonna use SATs and you know we Don't want to custody people's funds so We'll have the app just talk to Greenlight right and it'll be your node Running on your app um and that's kind Of cool because you know it's lightning So you can just transfer it you know if You've got some in-game currency in this Game you've got a lightning wallet over Here it's the same thing right you can Just transfer one of the Underappreciated things about green Light is because it's a node by itself You could have lots of different front Ends accessing it so you could you know

Have RTL you could have a game you Everything sharing the same node using Exactly the same front end uh sorry Exactly the same back end doing all that Control so um there are some really cool Ways to use green light that we're Starting to see people experiment with Is there is there much traction there I Mean that's a whole investment vertical From the last cycle right gamef and I Think the model is typically like they Issue some other token that may go up a 100 times but may also go to zero at any Given moment seems like you know just Using Bitcoin and lightning is such a No-brainer is is there much um traction Being made there it depends if you're Trying to make a game you're trying to Make a currency right uh if you're Trying to make a currency then you want Your own whatever um but the other thing Here is is there's and this is something Where where regulation makes sense right Um There's a big difference between being Custodial of people's funds and them Being custodial of their funds right From both an ethical uh and Regulatory Perspective if if if you're if if if you Are not the cust of the funds and you go Away or whatever rug pull or you go Bankrupt right you're a startup whatever Um they've still got their funds right Um and that's just what a much nicer

World to live in but also from a Regulatory point of view you're if You're deal starting to deal with Customer funds and things like that well Now have some questions um so the Greenlight model makes perfect sense for That oh thank you that's great that Makes a ton of sense um and then going Back to the wallet issue outside of Green what are some kind of wallet Recommendations that you have for Anybody um on their way to El Salvador Or something like that yeah so my Longtime favorite wallet has been Phoenix um by uh the async team um they Have been involved in lightning since The the original milon 2018 spec days um So they've been very active in and uh Spec developments particularly from a Wallet point of view um and doing a lot Of those those things um so uh that That's I've still got that on my phone It's still my it was you know for a long Time that was my go-to lightning wallet It is you know non-custodial has always Been non-custodial um very well thought Out very nice design um and and really Does some do some great things behind The scenes um they've just added Splicing um based on the splicing work That was pioneered in Coral lightning um Annoyingly they kind of beat us to Deployment um but you know uh it's it's Great to have you know a second set of

Eyes and everything else on that so uh They they because for them I mean you Know basically they're setting up Channels speculatively with users uh Based on incoming and rather than having To set up multiple channels and then at Some point they have to close them all Being able to splice funds in and splice Funds out on demand makes their service A lot more flexible so for them it was It was definitely a nice to have and It's based on the the splicing um spec Improvements that are an experimental Feature in cor lighting so um yeah it's Fantastic I love I love their work um And it's a they're a really good team Very cool so with with green um now Implementing lightning in the wallet so I guess we've got both major layer twos Now right we've got liquid and lightning What are the what are the benefits of That and what are maybe some other Wallets if any that are that have done That so as far as I know they're the First significant wallet that's done Both um which I think is great because It gives users a huge amount of choice As to what they can do um you know and I Think that actually opens really some Really interesting opportunities that You know I'm not going to um you Know I'm not going to like pre-announce Or anything here just I I there's a pile Of things that you can do on liquid that

Are interesting uh that that users want To do um you know the obvious being so Access to stable coins and things like That is it kind of an obvious liquid Feature uh but there's also yeah the Privacy things so um you know uh liquid Is very careful with um you know with Amounts and privacy and things like that That I think are quite interesting um And could be used uh you know could be Leveraged in a lightning context so you Know um expect to see more stuff in that Intersection I would say coming up okay Very cool you just touched on SP Splicing and earlier we talked about Some of these experimental features that You can flip on and off um can you Quickly explain what splicing and dual Funding are dual funding is the idea uh It's kind of an obvious idea that you You only realize if you're kind of Deep In The Weeds originally when lightning The first Lightning spec the 1.0 spec Came out um when you create a channel One side put the funds in I went hi Jesse I want to open a Channel with you And I'm putting These funds in you okay Cool I'll wait for those to appear on Chain and we'll go um the more Sophisticated way is to say hey I'm Going to put these funds in you go well Actually I'll put some funds into right So we kind of negotiate and I go okay Well then I'm going to have this change

Output and so rather than me just going There the transaction is going to appear Don't worry about it h TX ID um we would Actually negotiate it together and go Cool um because it's an opportunity I Mean it's slightly cheaper sometimes to Do that way um uh but also you know it Does allow us to have both sides put Funds in initially to a channel if they Want to and it opens the thing for Liquidity ads which is where basically Go cool I will you know in return for For money I will fund your channel right Uh it's an open spec so noes advertise Their their liquidity and they and you Can connect to them go cool I want to Take you up on that um on your offer Great uh I'll put this many stats in Therefore you'll put in whatever you Know your agreement is right so it's an Open Marketplace for for liquidity which I think is really important um and uh in In the lightning ecosystem so uh so That's dual funding now splicing is kind Of similar if you and I already have a Channel and go hey we want to change the Channel we want to like put more funds In we want to take funds out um you know That makes sense if you have like if you Think about um lightning is kind of a Hot wallet um and you know or your petty Cash but at some point it builds up Right you huh I've got a lot of funds in This channel I don't really need

Them I would like to push some of the Said that out to Cold Storage right at The moment the way you have to do it is You close the channel reopen a new Channel uh like close Channel spend some Of it out to your cold storage and then Reopen a new channel um well that's kind Of silly why hey you know our nodes can Talk to each other like cool I want to I've got this much funds in the channel Like it's half mine I want to take like Half of that send it out to this address There's going to be a new transaction And then it gives you the opportunity to Go okay well if you're reducing yours I'll reduce mine or like or this is Really useful for me I'm going to top The channel up whatever it is again we Negotiate what the transaction looks Like it goes on chain um and the channel Stays active the whole time but once the Full one's confirmed you can use the new Channel so technically you can use the Minimum of the two balances right you go Well if you're taking stuff out I'm not Going to let you start spending it now Because I know it's coming right so you Basically take the minimum um and once It's locked in you can go great we've we We forget the old one we're on the new Rules now you've got this much funds Available so um and of course another Twist is the zero comp where basically You effectively trust the other other

Guy to like get it right you go cool uh It's it's in Coreal lightning you have To Whit list beer for this uh we won't Let them do it by default well let know We got to wait for at least one confirm But um you know you can do it instantly If you're prepared to have a little bit Of trust in there that it's coming at Some point and what can users expect for This upcoming uh upcoming version 23.11 Right 23.11 of course for the November At least um we're up to rc3 uh which Will you know we've got we've got like Eight days it should be should be fine We'll make it uh um so one of the things Is that wbo's on by default so so large Channels is just enabled by default That's really nice um there's been some Cln rest improvements there's been like Improvements across the board uh that We're pretty happy with um one of the Cool things that happened this release Is that we finally completely got rid of The old developer builds um we used to Have you could turn developer on when You built it and you get a developer Version uh now everything's a developer Version you have to specify the Developer option and then you get access To all the developer things uh now that Can really break your note uh they're Designed for testing so don't do it but You know um it's just it's a nice thing We finally finally got that it just

Makes it a lot easier for us there's a Single single build and that's that's Everything um there's uh There's some new uh some new weight apis We working our way through this weight API where you can basically wait for Events that previously you would have to PLL for you say okay okay list list all The transactions okay right I'm Gonna Keep polling till something happens now There's a generic weight IPI you can say Wait for this thing uh you can wait for Things that have changed things that Have been added or things have been Deleted um and just you know it makes it For more efficient particularly when You're talking about really large notes Um so there's a whole infrastructure That's kind of we're working our way Through different subsystems that goes a Little bit more of that goes in every Release that's that's improved um and There's just generally um some pretty Nice uh across the board improvements That that I think people will like um And you know there every three months so There are some things that didn't make In this release that will definitely be A next release so uh we're looking Forward to those as well where should People that want to contribute to core Lightning where should they go for more Information and and what are maybe some Of the things that that you guys need

Help with right so there's the build on Layer 2 site and there's also our GitHub Site uh Um uh and we have you know as I said Previously we have bi-weekly meetings if That's time zone compatible for you uh That they're advertised on the build Layer to core lightning site um and we Talk about you know what's coming up and You know people just turn up and talk About things they working on things they Interested interested in and that's Really useful um if you're a developer Then the GitHub site is a pretty good Place to look for issues and and ask Questions uh we have a Discord as well Where you can you know turn up on the Dev Channel or or any of the channels And ask you know there are no foolish Questions um just ask uh and someone Will surely help you I noticed you've Used SATs a couple times in the Conversation today where do you stand in The uh the debate of bits versus SATs All SATs there's no point you know I Mean you know I I've been through enough Price changes now that're like you know Sat SATs is the standard um technically Um the the unit of account for light the Light network is mads like a thousandth Of aat um you know which is a little bit Ambitious because that's going to be a While before that's any significant Amount of money but technically you know

We go down to that it makes sense when Feeser percentage right so if you're Sending one at if if that's your basis How do you how do you account for that Now obviously when we settle on chain Eventually uh it gets rounded so the Miners get the the tiny tiny fraction of A SAT that's left over um but that That's how nodes account for each other We talking we talking Ms between Ourselves so obviously that puts me on a SAT standard okay got it and maybe to Wrap things up looking forward the next 12 or 18 months what what excites you The most about the the world of Lightning right wow okay so Um 128 in months I think we will see a Lot of really good improvements there's Some privacy improvements that we Definitely want to come uh that that are In in like early spec now um we're Seeing like tap rot channels so and Kudos out here to lightning Labs who've Really pushed this idea tap channels Quite hard it's been something that We've wanted to do but it hasn't reached The front of the queue where they've Really been pushing the spec work on Making that work um it requires a new Gossip system uh because we need to talk About currently to to to to tell the Network about a channel you have to Prove that you own it and that's very Much tied to the way channels work today

If we have a Tapo Channel and you want To prove you own it we obviously need Something different so it's kind of open Up the debate on on how do we do gossip At the moment because you gossip a um Now a private so one thing is private Channels become a lot more private at The moment you can kind of tell a Private Channel once it's closed you can See it's a two of two like why would you Do a two of two you're almost certainly A lightning Channel um with Tapo that Goes away uh they just look like normal Spins you BEC a lot L traceable now Obviously if you're telling Network by The way I have a channel and here I'm Proving I own the utxo then they know It's a lightning Channel um but even There there's some work uh some Experimental work going on to basically Uh reduce the amount that you have to Prove um you'll have to prove that you Own a utxo potentially but behind that You can have a number of channels so you Don't have to expose all your utxo now Even if you're a public node exposing Your utxos turns out to be a bad idea Because from knowing what your node what What coins your node owns um you can Then derive a whole of other anciliary Information right like oh that looks Like this one is also theirs and things Like that so it does leak more Information than we wanted to originally

And that's one of the reasons to kind of Wind that back the other that's Happening in privacy of course is the Bolt 12 work uh that's you know slow but About getting there um with onion Messages and onion routing which means That you can now um uh have a blinded Path which means that you can pay Somebody without knowing where they are On the network uh which is something We've wanted to do for a long time so The way it works today is the um you Know where the when you're paying Someone you know their node ID you know Basically where they on the network You' Got to find them don't know who's paying Them but there's no receiver privacy um That's a reasonable tradeoff to start With but think of the case of refunds Right um so I I pay you for something That's fine and you don't necessarily Know who I am great there I get all my Privacy but then you go oh sorry it Wasn't in stock I want to refund it at The moment it's like well okay well here Goes my either I have to choose between My privacy or my money right um that's That's unfortunate so even if just for That case uh you really want a way to go Cool here is a blinded path you can send Funds through this and it will get to me Right um but you I don't need to tell You anything about what my note is oh You're running one the biggest noes in

The network you must be Bitcoin Rich all That kind of stuff you don't you know uh You don't have to share that at all um So blinded paths are a big privacy wi so You know these these things just kind of Slowly improve the state of the network As a whole uh and give us definitely More options for things we can do oh That's very cool well really appreciate The time today Rusty and uh look forward To having you on more often in the Future fantastic thank you Jesse you bet Take Care

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