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Peter McCormack: Good to see you again. It’s going to be very difficult for me to do an interview with you without asking quite a bit about the past. I’ve been in this space probably a lot less than most people especially yourself. A couple of years and recently, I’ve been digging in the past, reading old Bitcoin talk threads and looking up old emails that were sent between various people at various times during the history of Bitcoin.

Peter McCormack: So, my questions may feel a bit basic at times but I’ve got so many things I do want to ask you. So, we’re a decade in. What are your overriding thoughts now? As you’ve essentially been in the project since the start.

Adam Back: I mean, I think people on the Cypherpunks list were interested in privacy technology, things like Tor, re-mailers for email privacy, and of the things applied cryptography things related to privacy that people were interested to achieve, the hardest and most Holy Grail application was a deployed electronic-cash system with some privacy and cash-like guarantees like bearer of immediate final settlement, and things like that.

Adam Back: That dates back to, what, 20 years now or something? And so it’s pretty exciting to people who were researching that, trying to figure out ways to make that work, and watching a couple of different systems try, and failing to make that work for various reasons. Like because they were centralised, or … I think that was the primary failure in the past, and also at the interfaces.

Adam Back: So Wey Dai and his B-money proposal, which was a 1998 proposal, said something interesting which was, he wanted to see an electronic-cash system without an interface to banks. Because one of the original systems by David Chaum, he made centralised electronic-cash servers with very good privacy properties, but the way he envisioned getting your money into and out of it, is you deposit money in a bank account. It would issue you coins and you could deposit them for a credit in your bank account. And so his company went bankrupt, and the double spend database was probably sold through the equivalent of eBay at the time or something. And that was the end of that.

Adam Back: I think that one of the most interesting things about Bitcoin, even though the privacy properties are worse … It is decentralised. It’s a fabric that can survive any one company. It’s very survivable. Individual companies can come and go, users can join or leave, and it will keep running as long as there is incentive for miners to mine it. Which is, you know, as long as there is a market value of any kind, that will be the case. The hash-rate might go up and down, and new equipment will be bought, different suppliers will be providing different services, but that survivability was always the missing ingredient before.

Peter McCormack: And do you think of Bitcoin now as still a project that can succeed or fail? Or do you think we’re at the point where it’s beyond that kind of beta feeling where it’s a success?

Adam Back: I think it’s … there’s a phenomena called the Lindy effect, which basically means the longer something has continued to be robust and survive, the more confidence people have that that will continue to be the case. And so it’s definitely a lot further along on that curve.

Adam Back: And I think another s … so I was hypothesizing in the past, that there should be a point at which it has a bootstrap. Where even if hypothetically all major governments outright banned it, it would continue in the same way that grey market goods are continued to be supplied, particularly in the electronic domain. Or let’s say, MP3-sharing, things like that. It’s not something that any particular government approves of typically, but it’s very hard to stop.

Adam Back: For electronic currency like Bitcoin, my hypothesised bootstrap was that everybody knows a friend-of-a-friend who would be willing to OTC trade for paper cash. And there’s pretty robust markets for OTC electronic cash these days, and there are like, millions and millions of users. And you do see very interesting evidence is the case, that this kind of bootstrap has happened, because some countries that have had a lot of Bitcoin interest, when on official terms they ban it, the OTC platforms see a huge spike in use and that means it’s time for the regulators to dial back their controls. Because they have more visibility if they regularise it than if they ban it, and it continues in the grey market, where they have no control. Less visibility.

Peter McCormack: So do you think in some ways that’s Bitcoin’s greatest achievement? That it has been able to survive despite whatever a government wants to do?

Adam Back: Yeah. I mean, it has a couple different uses, but I think the censor-resistant properties where you can, there’s no policy about who you can send to. There are no identities. There’s some kind of pseudonymity, privacy’s not perfect, it’s got a lot of traceability, but ultimately it’s very difficult for somebody to prevent you sending money to somebody somewhere else. And it has no awareness or care about which location the recipient’s in. And then you have the bearer properties, so it’s very hard to freeze, very hard to seize, probably harder to seize than physical gold coins or small gold bar in a safe or something because that’s a physical item that can be found. Where the Bitcoin, you’d never know ultimately if somebody put a reasonable amount of care in to it, it would be difficult to find the Bitcoin

short of contempt of court like things where you have some evidence they have some, and you demand they turn it over. Okay, that’s the ultimate recourse.

Adam Back: But for users I think an interesting concept is the true name concept. So there’s a science fiction book by Vernor Vinge called True Names. And it’s basically the concept that if somebody knows your name, they have some kind of power over you. Where if you’re kind of obscure, nobody knows who you are, or that you have an involvement in Bitcoin or that you’re involved in some online discussion group about politics, or current events or what have you, then you’re much more immune to interference.

Peter McCormack: Sounds very Jameson Locke.

Adam Back: Yeah. I mean I think, you know, some people who have acquired Bitcoin have done so in different ways. Some people have just you know, wire-transferred money to an exchange and bought the Bitcoins, and basically at this point all of the exchanges have KYC information and have a scan of your passport and so on. So those Bitcoins are pretty much linked to you. But there are people who had more of a privacy thought in mind early on when the accumulated Bitcoin, or they did so before there were exchanges. So their Bitcoin were you know, bought in a coffee shop at different times for a few hundred dollars in cash or something like that. So those are much less linked. And so from an asset-protection and not standing out as an easily identifiable person who has Bitcoins, those Bitcoins are in a way more valuable for that use case.

Peter McCormack: Right. Okay. So, whenever people ask me about Bitcoin, there’s a handful of podcasts I point them in the direction, specific interviews. And there was one you did with Epicenter a while ago. I’m going to ask you a question they asked you and that’s a very simple question, but the answer was, I found really interesting and I want a version of it on my podcast. So, it’s a very simple question, but what is Bitcoin?

Adam Back: What is Bitcoin? So … it’s a lot of things I guess, but it’s a kind of virtual currency. So I think the shortest version to somebody who isn’t aware of it and maybe isn’t computer-science specialised skillset is to say it’s electronic gold, basically. It’s also a bearer electronic cash.

Adam Back: I think the gold-like aspect is just to say that it has scarcity, there are a maximum number that can be mined, and the cost of mining goes up over time as the scarcity increases. And that it’s censor-resistant, and hard to seize and freeze. So I think that these are the key and interesting things.

Adam Back: And some people think about Bitcoin to say, because there are different things you can use it for, different users have different benefits in mind when they use it. So some people who are thinking, “Oh, this is great. It’s very cheap, low-value payments, lower fees.” And other people were more focused on the unseizability, and others were looking at it as an investment concept, right? Those former two properties are very interesting, so they’d like to invest in the potential for future value of that.

Adam Back: And people with different use-cases have different ways they would want to see Bitcoin optimised, so I think that caused some of the past debates about scalability and things like that. But Bitcoin has some pretty interesting properties that are interesting to many people, and you would want scalability for the primary reason that you would want anybody who wants to use those features to be able to. And to be able to do so at a reasonable cost. I think with scalability technology like Lightning, that’s closer to reach.

Adam Back: Lightning is being actively worked on for a couple years now, and is getting much easier to use. More channels, more users, and very fast adoption curve. Very high energy. Lots of people doing software development at the protocol level and the application, wallet and integration levels. So that’s well underway at this point. And it is a slightly different use-case, so you would use like a wallet that supports Lightning. I would expect that most smartphone wallets will support both within the next six months to a year, and actually if you’re using a smartphone wallet it will probably be by default making and receiving Lightning payments because it’s a wallet I think … on a smartphone you would typically not want to put more than you’d carry on cash in a physical wallet. And those are the kind of amounts that Lightning can cope with very well. And the security trade-offs are reasonable.

Peter McCormack: Okay. So I’m going to ask a few historical questions. Because it’s really interesting from me and I think for other people who weren’t around then.

Peter McCormack: Firstly, are you more excited now or than you were when you first discovered Bitcoin and the potential. Actually, let’s go with the question first. When you first read the whitepaper, did it feel different than all the other projects or was it just another attempt? Was this just another digital money and we’ll see what happens?

Adam Back: I did think the decentralisation was interesting, and you could see a connection to Wei Dai’s B-money, and Nick Szabo’s bit-gold concepts, which were kind of outlines. Not directly implementable. So I think that was interesting, and I had two thoughts. One of them is that it’s really not very private, because the previous electronic cash systems were providing extremely robust cryptographic privacy, but were only able to do that via a single server. So they had single-point failure.

Adam Back: Another thought was the security of the finality is unusual. Normally in cryptographic systems, let’s say you’re using PGP encryption. The cost to encrypt is a fraction of a second. The cost to decrypt without the keys is hundreds of years of supercomputers. So really asymmetric security model. Whereas with Bitcoin it’s more like an evenly-matched arms-race between the people that want to see the system operate normally, and some entities with mining equipment that want to disrupt it. And so the lack of an amplifier on the defensive side took some getting used to but I think ultimately, money works because people want it to work. And Bitcoin has benefited from … Even people who are on the attack side in terms of breaking protocols and hacking things find Bitcoin super interesting and so they’re reporting the bugs rather than trying to exploit them. In the early days. At this point, it’s quite robust.

Adam Back: So those were two thoughts. And then the third thought was, “Well, that’s pretty interesting. Let’s see if it bootstraps,” because you have to bear in mind that was zero market-value, no market-place, transactions, but just for fun basically. Like, the pizza transaction and things like that. And just people paying people for no reason. Like no exchange of goods. Like, “Here, have some coins to show that it works.”

Adam Back: So those were two thoughts. And then the third thought was, “Well, that’s pretty interesting. Let’s see if it bootstraps,” because you have to bear in mind that was zero market-value, no market-place, transactions, but just for fun basically. Like, the pizza transaction and things like that. And just people paying people for no reason. Like no exchange of goods. Like, “Here, have some coins to show that it works.”

Adam Back: So I thought all that’s pretty interesting and that maybe we’ll see if it bootstraps, and maybe as that became evident I was thinking, well, my skillset for most of my career has been in applied cryptography working on protocols including electronic payment protocols with cryptography. That maybe I could use that background. As the previous systems had very good privacy but didn’t bootstrap, here we have something with kind of weak privacy that is bootstrapped. Maybe we can incrementally improve on it. I mean, it’s much more challenging to have those kind of privacy features in a

distributed system, but there are different things you can do. So that’s kind of where confidential transactions came from, and some other ideas.

Adam Back: Confidential transactions got implemented in Elements open-sourced project that Blockstream worked on in the Liquid Network, which is an exchange settlement kind of Bitcoin sidechain.

Peter McCormack: I’ve got some questions on that coming up soon as well. When was the tipping point in the early days when it went from being, “Okay, this is an interesting project,” to “Okay, this is really exciting, we’re really on to something here?”

Adam Back: I think I thought the concept was very exciting, because you have got to bear in mind I spent a lot of my free time for probably half a decade there in the late ’90s early 2000s along with a number of other people trying to figure out different ways to make it work, or puzzling over previous electronic cash systems to make them peer-to-peer re-spendable or achieve other properties.

Adam Back: As you saw with Wei Dai’s B-money, and Nick Szabo’s bit-gold that the idea that you could use Hashcash and proof of work to mine a coin and try to make that decentralised was something that occurred to people within a year of being familiarised with the proof-of-work concept. That concept was there, but there were technical hurdles. Or technical economic-incentive game-theory hurdles that people didn’t manage to overcome, that Bitcoin finally did.

Adam Back: So definitely the idea that this is at a very interesting intersection of crypto-technology and societal impact, which is something that I find interesting in general. Like, PGP and Torrent. Things that shift the balance of power. And the internet itself. Publishing, and so on.

Adam Back: I mean, I certainly hoped it would bootstrap, but it wasn’t clear if it would. And there was a previous electronic cash system by David Chaum. He moved to the Netherlands, operated a company called DigiCash. And there was a demo electronic cash server, that he set up. And the company made the assurance that they would keep the demo running and it would never issue more than a million coins. And you could ask for coins just by emailing. They would send you some, like a faucet. So I had some of those coins, and a few …

Adam Back: Yeah, some of the people on the cypherpunks and cryptolists, it occurred to them to try and seize this opportunity to bootstrap this currency. So they did. Like, they sold T-shirts, and like, low to medium value items using it. And they figured a few thousand people, because it only had a million units, would maybe achieve a stable value. And because they called the tokens Beta Bucks, like dollars, people had a hint that, “Well, maybe it should be worth a dollar,” so they would typically use that as an exchange rate. So that was in progress, and I’d sold a couple of things on it as well as probably a few hundred other people. And then DigiCash went bankrupt, and that was the end of the double-spend database and so your coins were not provable.

Adam Back: That electronic cash system is, if I give you a coin you have to rush and deposit into the bank, otherwise I could spend it somewhere else and you wouldn’t know. So that feature was lost. That was informative.

Adam Back: So the idea that Bitcoin might bootstrap was connected in my mind with that event, but still it was an unknown, right? So … I think when it got maybe up to a dollar, which took quite a while, for there to be exchanges for the price to be a dollar, that kind of felt like, “Okay, well that sounds more like reaching the same kind of stage as the DigiCash kind of unsanctioned experiment by a bunch of guys on the mailing list.”

Peter McCormack: And then when we hit $20,000 how did you feel?

Adam Back: Well, that was like a pretty good price, and personally I’m expecting that Bitcoin has enough utility and potential value that we’ll see that and more in the future. It’s always had a lot of kind of deep volatility cycles. I see the market price mostly being driven by the future potential, and investors that are trying to invest in that future potential, or are interested in the digital gold asset protection, unseizable characteristics as kind of a counter-cyclical or insurance against geopolitical instability basically. And gold has some of that too.

Adam Back: So Bitcoin has some advantages to gold too, you can send it a distance at a very low cost, you can verify that it, it’s equivalent of assay it, so you know that it’s a real Bitcoin. Even a smartphone will refer to servers that tell you that and you can verify it yourself for pretty low cost. With gold, you have gold ETF inflation. Physical gold is sometimes being mixed or forged or what have you. So you could see Bitcoin becoming a competitor to gold. And if you look at private ownership for gold, for which there are various estimates for, that would already imply a quite optimistic price for Bitcoin, per Bitcoin. As people say, when you think about it, there are only going to be 21 million coins. There are-

Peter McCormack: A lot are lost.

Adam Back: … billions of people in the world. Some reasonable percentage of whom might find it interesting to own a little bit of Bitcoin.

Adam Back: There certainly are some countries where there is a kind of tradition of having private ownership of gold as a form of investment or savings, or where the local currency is fairly high inflation or something, just as a way to hold on to value. So Bitcoin can, I think, potentially compete in that area.

Adam Back: And people talk about the volatility, but I think longer term that will decrease, and presumably at some point it will get to the top of the adoption s-curve. Like internet use and cell-phone use where basically everybody who is interested in the use-case has heard about it and has adopted. And at that point, you should be at a more stable state. Now of course, gold is still relatively volatile, but I can see it getting to something like that. And that would be more of a stable value.

Peter McCormack: Right. So, I listened to an interview with Murad this week on Pomp’s show. And he said, “We need a volatile Bitcoin to become a global digital asset. The only way it can do that is to be volatile. To increase in price quite quickly. So I don’t find the volatility to be something I worry too much about.”

Peter McCormack: Do you find … Back to the other question I was asking. Do you find it more exciting now that Bitcoin has a global infrastructure, it has institutional interest, it has various different responses from governments, it’s a whole new set of problems to negotiate? Do you find this more interesting now than back when you had originally discovered it and were looking at whether it could bootstrap? How do you compare the two?

Adam Back: It’s definitely bootstrapped in several regards, and also in that it would continue even if somebody tried to shut it down. But also, some governments have kind of officially discouraged use or allowed use but discouraged exchanges, or different trade-offs. But for the most part it seems to have been accepted and regulations have been created to accommodate it in a lot of countries.

Adam Back: But I think it’s interesting to look at the differentiated use-cases. So, the use-cases that only Bitcoin can do, because if you look at those, those are the areas where existing systems can’t compete with it. So I think those are the censorship resistance, permissionlessness, you can just install a smartphone app and somebody can give you some money. There’s no registration, sign-up, approval, kind of process. And then censorship resistant payment, and bearer ownership are things that basically banks and other forms of payment can’t compete. And there’s a use-case for that in the world. There’s a use-case for physical cash in the world, and most societies acknowledge that there’s a need for physical cash for trade-off between privacy and state controls or things like that. So Bitcoin provides that in the internet domain. So I think the use-case is here to stay and there’s not really any scenario where that can go away.

Adam Back: But I do think it’s those unique differentiating things that were the most interesting thing to me in the beginning, and still now. Where some people may have been more kind of, investment use, or looking with interest when … whether a sovereign wealth fund would buy Bitcoin or something. So I mean, of course it’s fine and interesting if they do, but I don’t think that’s a differentiating use-case. Right? That’s more like a gold investment by the central bank of a country as a gold reserve or something. The interesting use-case is the end-user self-sovereignty that they can achieve by having some Bitcoin.

Adam Back: Now of course, companies in countries invest in all kinds of things including startups that are making self-publishing software or encryption software so it’s certainly to be expected that different investment vehicles would invest.

Peter McCormack: Well. Okay. Last kind of historical question. During the last 10 years, has your thought process … Has there been any significant changes in your opinion or thought process with relation to Bitcoin?

Adam Back: You can understand Bitcoin at different levels, but I think even the people who are implementing details of the protocol or thinking about cryptography protocols, or incentives and game-theory, are effectively still learning things, which might be surprising to some people. But I think for example, the fork issues that happened last year with the UASF … So apparently yesterday was the anniversary of the cancellation of 2x, Bitcoin 2x fork. So I think the way the game-theory played out there was instructive to everybody with all viewpoints. And the fact that Bitcoin completely shrugged off basically a large segment of the business and mining community, and said, “No, this is what the users want.”

Adam Back: And the economic incentives basically forced that to happen, was very positive for confidence in the long-term store of value potential and immutability which I think is pretty key. You can’t have like a business lobby or special interest coming along and saying, “Well, this is a nice internet protocol you have here, but we want to modify it to optimize for this use-case.”

Adam Back: Actually, there’s a quite interesting analogue with internet protocol governance going back to I think the early ’90s, where within the IETF, that was largely universities and academics, and practical developers working on protocols, and as internet companies building browsers and different appliances became larger and more influential, some of them started to think that they should have control of the internet protocols. And so they tried to bring about a governance change in the internet, in the IETF system so that companies could get a formal vote and they would be able to basically coordinate between a few companies to haggle over what they were going to vote on and change internet protocols. And it’s similar to the UASF situation, that ultimately the people who were historically working on internet protocols were able to reject that.

Adam Back: I think that was a very good thing, because a very commercialised control would be a much less valuable internet. It would be more restrictive and optimised for commercial interests. So it would trend back towards a kind of walled-garden centralised control thing and I think a lot of value actually comes from it being an open network with protocols that are basically open and for the users’ interest. So I think that was a mirror in Bitcoin going through that phase. To say, “No, actually, we want an open protocol process where basically there’s a decision-making process where there’s technical consensus, which means that the technical community agrees that an improvement has no significant and valid technical defects or better alternatives, and then also consensus among the users and investors and so on.

Adam Back: Some people were convinced and proven completely wrong about the influence of miners in the situation. They literally thought that miners decided on the protocol by the blocks they produce. But, some people saw it, some people didn’t. But the forcefulness with which that was proven, and the short time-period in which that view folded and collapsed was instructive and interesting. It’s basically like the-

Peter McCormack: Is that BIP148 proved that point?

Adam Back: Yeah. I think so. And the sort of game-theory that led to the cancellation of 2x, which I think was that they realised that the miner’s support was only philosophical. Because basically if the miner is mining gold, and they happen to have a big plot of copper to be mined over there and some business guy saying it would be better for us if we mined copper instead, and the miner said, “Yeah that would be good for us, we have a copper mine.”

Adam Back: Then we support that philosophically but then they realised that the market price for copper is like 1% of the price for Bitcoin. They’re not going to mine that for very long or they’ll be bankrupt, right? Presuming the cost of mining is the same. So I think the miners basically conveyed, you know, we can’t mine unprofitable things more than like, half a day or something. So, it’s not going to work unless the market agrees. And it’s kind of the same thing for companies right? If they’re selling something different that people don’t want to buy … basically it was kind of a market influence story.

Adam Back: And the other subtle thing is that the users who are running full nodes and the businesses … and many of the smartphone wallets kind of cross-check against a full-node these days … the software decides what’s Bitcoin to them. So if the miner mines something which is incompatible with that, they don’t even see it. It doesn’t show up in their software, it doesn’t look like they got paid. And so, essentially the miners have to follow those rules, where some people had the misconception that they decided those rules and the rest of the world would automatically follow. And that’s just technically not the way it works, in fact, in practice.

Peter McCormack: Yes, quite interesting. So another journey I’ve been on is going through the history of the scaling debate. And just seeing it the different points, the different views people have from the very early days. During that I found a quote from Barry Silbert where he said there were essentially three parties, miners, companies and devs. And he said, “When we tried to come to an agreement and the devs weren’t part of the conversation it was very easy to come to an agreement between the companies and the miners.”

Peter McCormack: And I thought, well of course, because it’s entirely financially motivated whereas the devs seem to come much from long-term user perspective, philosophical perspective. So I just kind of found that a very strange statement.

Adam Back: Yeah. I mean, I think it was no doubt done with good intent in the sense that as well as having a commercial interest they were interested in seeing adoption. Which, basically everybody is too, but at what cost? So-

Peter McCormack: And in what timeframe.

Adam Back: Yeah, yeah. In a real practical basis. I think there is another interesting aspect of that which is the three groups you mentioned, the businesses, the miners, and the developers, is that there is another very important and ignored group which is the users and their economic views. And that’s basically what won the day. And actually, the developers were very conscious going back many years ago that they don’t want control, and they don’t even want the appearance of control, because that’s risky. Bear in mind in the early days it was unclear if Bitcoin would be banned in major countries for example, right. In fact the UASF and BIP148 was not supported by most of the developers, so that was really more grass-roots. Sort of a small group of like a couple developers, one of them pseudonymous in fact, which is kind of interesting. Shaolin Fry implemented that and a couple of technical developers supported it vocally, but largely it was user groups, a number of small to medium sized businesses, and Bitcoin embassies, and Bitcoin meet-ups and so on, that were most vocal about it.

Adam Back: I think the other thing that helped, is you got a preview of what the market view would be. Some of the businesses would say, “Well, we have a million users and we represent them,” and that’s hard to evaluate in practice, right? They don’t actually know that if they continued down that path if they would have zero users the day afterwards. And so the Bitfinex put out a future, which then allowed you to see a market price. And the market price was very low compared to the business and miner support. So in the miner support, which turned out to be philosophical and not economically able to follow through on that, was kind of inverted. The price was under 10% and I think the miner support, the philosophical support was in the 90% at one point. But nevertheless, the economic viewpoint of the market, saw pretty much immediately and prevailed with pretty convincing finality.

Adam Back: So a lot of good things to learn from that. I think a number of the people involved in the 2x were kind of on the fence, or were a bit hesitant toward the whole thing. They just wanted to see some progress on scaling. Maybe weren’t quite as connected with the technical consensus process that comes from the ITF history. So I think they were reasonable debates to happen about it, right? I do think that this kind of 128 MB block size stuff is nonsense. That doesn’t make sense.

Peter McCormack: A new scaling war?

Adam Back: … Oh, yeah, I’ve barely paid attention to that, but I mean, some interesting things may come out of it because now you’re talking about the Bitcoin cash having another fork within itself into two or three forks-

Peter McCormack: Bcash-cash.

Adam Back: … yeah. I mean, what is it …

Peter McCormack: SV …

Adam Back: SV? I’m not really sure about-

Peter McCormack: ABC …

Adam Back: … yeah kinda, they need a better name than ABC, but okay. Yeah. So those two groups … I mean, it will maybe be instructive to see how that plays out because some of the players in that seem to be going at it with a different perspective. Like, at least claiming or posturing, that this time the miners are going to be more aggressive and burn money for a period of time. So the whole thing is within a small percentage of the overall hash rate, because the hash rate of the whole thing is like, 5%, 6%, 7% or something of Bitcoin’s hash rate. So you’re talking about sort of 2% or 3% pitted against 2% or 3%, but their seem to be a couple of big players who might have the pockets to kind of have a hash rate fight.

Adam Back: But it will be interesting, because I suspect that even so, it will come down to economic views of the users in that.

Peter McCormack: One of the things that I thought was most interesting out of all that, that I saw yesterday, was Roger Ver’s tipping his hat to Core about contentious forks, because he’s essentially experienced one himself now.

Adam Back: Yeah.

Peter McCormack: And I think he’s probably reflecting on that and going, “Okay, I get it now.”

Adam Back: Yeah.

Peter McCormack: I thought it was quite interesting.

Adam Back: Yeah. I think it’s positive for people to acknowledge that they’re wrong about something, and in a technical domain, people are very happy to do that generally, you know. The have a technical view that their protocol version is better and they argue forcefully. And then somebody points something out and they go, “Oh. A-ha. Yes you’re right. Okay, forget what I was saying. That was rubbish.”

Adam Back: So there’s no kind of pride in like, my proposal is really striving to find the best solution. And if somebody had a better solution, you’re excited to adopt it. It’s harder for people to do that in politics, and I think a lot of people participated in the scaling discussion as if it was politics, or something. Right? Which is not a good direction, because that’s where the Fiat currency is. It’s controlled by politicians, and banks that are influenceable in a pinch by central banks that are subject to moral hazard, ultimately. The Genesis block quote about moral hazard from Mervyn King and so on.

Adam Back: I think some people learned from the previous fork, and some people are learning from the new fork. But, people learn by different ways. Some people learn by analytics, some people learn by doing and seeing.

Peter McCormack: It’s kind of one hell of an immune system that Bitcoin’s built up this last 10 years. I was discussing it with somebody else, and I was saying these anti-fragilities, its immune system going through the civil wars, the Mount Gox collapse, Silk Road collapse, China banning … so many things. It’s kind of incredible it has survived. Why do you think it continues to survive because of that?

Adam Back: Well, like I said, I think-

Peter McCormack: Lindy effect.

Adam Back: … well, Lindy but, I mean, I think the anti-fragility is basically the people with interest to see it, to use it, and benefit from it, and see it as socially valuable. So they will do things like argue for UASF, and adopt install 148, and make economic statements in the market, like short the future, or sell one coin and buy another. So I think the economic forces are very important. And the technical anti-fragility is also important. If there are technical defects found, people will fix them. So it’s kind of like aircraft crash investigation becomes more robust over time, because any issues of at technical nature are fully and thoroughly investigated, and robust fixes put in place and deployed.

Peter McCormack: That’s my favourite, one of my favourite shows.

Adam Back: Oh, I’ve watched those. They’re great.

Peter McCormack: So, they actually got me over my fear of flying. I used to have a real bad fear of flying, and I’ve watched so many of those, it’s like, they’ve kind of fixed everything. My dad was an aircraft engineer, and he said that the final problem to fix is relying on pilots, because the majority of problems come down to them.

Peter McCormack: Wow, so we’ve covered … obviously we’ve covered a lot, and there’s probably a hundred more questions on the history I’d love to ask you. But I do also want to ask you about Liquid, because that’s the project of the moment. Some people are not going to understand what a sidechain is. So can you give the briefest explanation of what a sidechain is?

Adam Back: So it’s kind of an auxiliary chain. So you’ve got the main Bitcoin chain, which I think is the most robust and secure, partly because of the economics of the situation. Network effect and the amount of infrastructure, like ways to buy and sell, connections to merchants, things like that. So there’s an interest to build additional layers. So one layer is Lighting, which is on top of Bitcoin but preserves most of the bearer properties of Bitcoin. Security model’s a little bit different, but ultimately you have automated recourse to the Bitcoin chain.

Adam Back: Sidechains are another layering technique. So it’s a way to make another blockchain that is connected in some technical way to Bitcoin, and be able to move bitcoins into the sidechain and use them in there, and bring them back out again. The key part of that is that there is some firewall between Bitcoin and the sidechain, so if the sidechain were to have a technical issue, it wouldn’t affect Bitcoin. It would only put at risk people who had opted into that sidechain. So it becomes a vehicle where people can try new things, and that’s exactly what we did.

Adam Back: With the Liquid sidechain we implemented confidential transactions, and confidential assets which are pretty interesting cryptographic things that have some quite good cryptographic security assurances, and basically make similar security assumptions as the digital signatures used in Bitcoin already. So there’s much less technical risk than the SNARKs and other things that people have contemplated in some alt-coins. But nevertheless, it’s a new thing, and it has different trade-offs. Those transactions are bigger.

Adam Back: The kind of sidechain we built is a federated sidechain. So it’s not being mined, rather its blocks are being signed by two thirds, or over two thirds of members. And the members are exchanges and institutional traders, and things like that who anyway have the infrastructure to host in a secure data centre like their hot wallet and their cold wallet and things like that. So we give them another box with a hardware module in it that is a block signer

Adam Back: So, there’s a peer-to-peer network between them which users can join, and receive and validate blocks similarly to the way you do in Bitcoin, but the blocks are actually … the analogue for miners is this fixed set of signers. And so one of the interesting things about Bitcoin is that miners can join and leave dynamically. And actually you don’t even know who they are, they’re kind of anonymous. And that’s a feature. So with a sidechain, there’s a different trade-off which is it provides less assurances in some ways, because it’s a fixed set of signers. I mean, that could be changed with software or with users agreeing to port the state of the chain into another set of signers.

Peter McCormack: So, it’s slightly more centralised?

Adam Back: Yeah. Yeah. And the use-cases for …

Peter McCormack: But is it almost like, sorry, so it feels like you’re almost describing like a settlement layer into the exchange, so they can trade with each other quicker, faster, but they can settle back to the main chain?

Adam Back: Yeah. So, you can take sort of these pegged Bitcoins which are called L-BTC, you can take them back to the main Bitcoin chain, and if you’re going to cold-store them you would be advised to do that because they would be more secure. But what Liquid is providing is an alternative to leaving Bitcoins in the custody of a single exchange.

Adam Back: So what you can do is withdraw Liquid Bitcoins and other Liquid assets from an exchange into a hardware wallet or a smartphone wallet. And now you’re not vulnerable to the custody-failure of a single exchange, but you’re still trusting this automated peg that is secured by the hardware modules and all these servers. But you know, if you were to consider the scenario where all of those businesses decided to steal your money. It would take two thirds of them, so 11 out of 15 at the moment, in order to take the Bitcoins that are held in the automated peg. So you know, there’s certainly been a spotty history, further in the past more than recently, individual exchanges have failed, or lost custody of funds, or suspected that the exchange operators might have even taken them and pretended to be hacked or something. When you have funds out of the exchange, in Liquid format, you are less exposed to that. Because an individual exchange could do its worst, and it wouldn’t be able to take the funds.

Adam Back: So the idea is basically, because the network’s faster, it’s more plausible to keep your funds off the exchange and deposit them when you want to trade. And to be able to take arbitrage spreads, you want to be able to move money quite quickly, so one of the bottlenecks today is that more on the Fiat side it takes days sometimes to get money to an exchange. And by the time it gets there, maybe the spread is gone. So it’s kind of frustratingly slow. You can see the trades sort of drying up while you wait for your transfers.

Peter McCormack: And the same time though, and therefore, this could probably kill off a lot of the arbitrage opportunities?

Adam Back: Well it’s a trade-off. You get deeper liquidity, so basically you get more volume and the spreads become lower. But the overall volume grows. So there are reasons why this is beneficial to driving trade volume in general other than the arbitrage. Which is, you get more liquid and deeper markets. So sometimes people try to do a transfer Bitcoin, sell it and take a local wire-transfer. And sometimes they fail today, because liquidity’s too small in some

countries for like a medium sized business transfer or something. So you get more use, because those liquidity problems get fixed, and lack of liquidity has been one of the factors the regulators have used against approving ETFs so far. So it’s another input into having a deeper, more liquid market.

Adam Back: And the other think is user trust, right? So if users are able to trade with lower trust, they will be more inclined to trade. So other than having coins in your own custody and then depositing to trade them, there is a possibility to do a kind of atomic trade. So two users can have assets in their wallets which are managed by the automated peg, but they can place an order on the exchange while keeping their own custody, so they can use the exchange’s order book and matching, but they haven’t deposited their coins. They’ve sent a partially signed transaction to trade. So let’s say I want to sell a bitcoin for $6500. I sign half of the transaction to swap one bitcoin for $6500 and you do the other half because you want to buy a bitcoin. And then that can get matched in the exchange order books. All the exchange has is it’s partially signed orders, so the worst that could happen is somebody could be forced to pay $6500 for a bitcoin, and they can do that without hacking the exchange. They can just go on the market and do that.

Adam Back: So it presents a lot less risk. Ultimately you should be able to transact without exposing yourself to individual exchange custody. So that’s a kind of incremental step forward for today.

Peter McCormack: Right. So are LBTC collateralised by real mainchain bitcoins?

Adam Back: Yeah. What happens is there’s an automated peg. So as a user who wants some L-BTC you would probably go to an exchange and deposit Bitcoin and they would do it for you. And let you withdraw L-BTC. And that’s The Rock, which is one of the early people to implement this and make it directly available to users, that’s how they do it. So you can deposit Liquid Bitcoin or main chain Bitcoin, and you can withdraw main chain Bitcoin or Liquid Bitcoin. And they manage a pool of Liquid Bitcoin to do that. So they’re kind of swapping it for you.

Peter McCormack: You can’t create Liquid Bitcoin without real Bitcoin?

Adam Back: Right. Yeah, so the full nodes verify that. So the functionaries verify if, but you as an individual user, if you’re running a full node, you run a Liquid full node and you also run a Bitcoin full node. And it will complain if you don’t have a Bitcoin full node running to check against. If it sees a transaction coming on the network from somebody claiming to peg in, it will check that actually those funds exist on Bitcoin where they claim to be, and that the Bitcoin node agrees that those are real valid funds, verified by the Bitcoin node, and that the peg-in transaction is valid before it will recognise it and show it to you as Liquid Bitcoin on your node.

Adam Back: Running a full node on Liquid will be a little bit more expensive than Bitcoin, because these transactions are bigger and they have lots of crypto in them. Kind of like dozens of signatures per coin. But, you know, it’s within reach of a power user to do it. You can run it on a desktop, or a fast laptop, with a consumer internet connection and keep up. So it has that degree of self-reliance that you can see that what’s happening is what’s claimed to happen. Now, of course you are trusting that the exchange is operating the full … the functionaries we call them, the hardware servers … don’t gang up and two thirds of them take the Bitcoins out of underneath. If that would happen, you would see it, but there wouldn’t be much you could do about it apart from legally complain that they stole your money or something. Right?

Peter McCormack: There’s no … the game-theory isn’t there to do it though, right?

Adam Back: I mean, well, right. The operators of the network, they’re not miners so they don’t get a mining reward, but they economically benefit from the increased volume of faster trades. And so they have an incentive to see the continued operation of the system. There’s a different kind of incentive, but there’s an incentive to not interfere with this operation basically.

Peter McCormack: Okay. Like a weird comparison. You’ll probably hate it. But it sounds a little bit similar in some ways to EOS in terms of…

Adam Back: I think one key difference-

Peter McCormack: By the way I don’t like EOS but …

Adam Back: … yeah, I don’t know a huge amount about it, but I think one key difference is that it’s an automated peg with hardware modules. Where as far as I understand it with EOS there’s a lot of discretionary behaviour and phone-calls where things are decided and things like that. So there’s no mechanism for anything like that in Liquid. So it’s a peg, but it’s automated and it’s enforced by hardware modules.

Adam Back: It’s for traders, right? So people who are trading on exchanges, the exchanges know who they are. So it’s not like permission less, censorship-resistant assurance, anywhere near what Bitcoin would be. So for people who are looking at the use-case of benefiting from Bitcoin’s censor resistance and bearer status and things like that, they should use the Bitcoin chain. Liquid is a different trade-off. It’s another layer too, and it’s an incremental improvement over giving a single exchange sole custody of your funds. That’s it. Right?

Adam Back: If the alternative was you deposit money onto an exchange

and you’re worried that they exchange will make a technical failure

and lose all the funds, okay, Liquid will help you because you can

take them off the exchange until you’re ready to trade, knowing you

can deposit them within a minute or two.

Peter McCormack: Right. Okay, that makes sense. Is it trustless?

Adam Back: No. So …

Peter McCormack: Apologies.

Adam Back: No, no there was a healthy discussion on that topic over the last few days. The point is that …

Peter McCormack: I had to ask …

Adam Back: That’s fine. So, the point is that you can validate what’s going on. Liquid has been running since late September but we’re playing catch-up releasing software to support different features and there are more things to come as well.

Adam Back: We’ve released the block explorer that can inspect Liquid network transactions and Bitcoin transactions, so it’s a Bitcoin explorer too. And we also released the full nodes, so people can run a full node and have a higher assurance that this information is current than looking at the block explorer, which we’re running. So you have to trust us that the information reflects what’s actually happening in the network. So you can inspect it, and I think before we did that … Every time you release a new technology that’s kind of complicated and has different trade-offs, people try to wrap their heads around, “Okay, what does this do? What is the security model? Who can use it?”

Adam Back: And I think people had an assumption that it was exchanges only could transact and hold assets in it, or that it was a private network and you wouldn’t be able to look at it. And that wasn’t the case. But, putting full nodes into people’s hands and they themselves as power users being able to create an asset on it and get some Liquid Bitcoin and transact with it peer-to-peer … Oh. That made the point for them. “Oh, okay, this is, you know, you can transact with this more directly than we realised. That’s cool.”

Adam Back: But the trust model is what it is. It’s a trade-off, and it’s an incremental improvement on single-exchange custody. But the assets in it are, particularly the Liquid Bitcoin, are IOUs to that automated peg. And if that automated peg were to fail in some way, you’d have an IOU. You wouldn’t have Bitcoin. So it’s not as bearer … so I think the kind of indirection is, you have closer to trustless control of an IOU, but what good is control of an IOU if the person who has the actual assets won’t give them to you? That’s the distinction.

Adam Back: That’s inherently the case for many types of assets. Bitcoin’s a special asset class, which is directly bearer. Liquid Bitcoin’s are not as bearer. There’s an automated peg that you have an IOU to. But other assets that you see in blockchains like, Fiat coins, US dollar coins, Tether, Gemini US dollars, and others have some inherent custody risk. Which is, does the company that has the funds in a partner bank’s account dip into the funds? Or does the bank seize the funds? So you have that kind of risk. And that’s a palpable risk, because it’s still pretty hard in some places for exchanges to maintain stable banking relationships. So it’s typically not that they had the funds frozen, but the bank decided to stop offering services and they have to go find another bank and transfer the money. So there’s that kind of risk, that sort of custody risk.

Adam Back: Another one is people have used colour coins and tokens, and all different terms for it, but basically equivalent of some kind of shared interest in an enterprise. So whether that’s a profit-share, or a share ownership, or some kind of token, there is trust that the money that goes into it, will the company even build a product? Or keep the money? That’s definitely happened in a lot of cases. If they do build a successful product will they share the profits with you, or will they keep them? And even completely aside from blockchains, for example, with a Kickstarter that went into the Oculus Rift, the people who funded that company got some alpha-hardware, and the founders of the company sold it for billions of dollars.

Adam Back: So you have to pay attention to what you’re buying. If you’re buying a piece of alpha-hardware, or kind of a vanity token that shows, “I was there. I donated to build the early stages of this project,” doesn’t mean that they’ll benefit. And typically the investment contracts on a lot of the historic blockchain tokens that claimed to be investments, have very defective investment contracts. They’re kind of anti-investment contracts that say it’s a donation if you read the fine print.

Peter McCormack: Wow that’s interesting. I interviewed Brendan Eich, and obviously researched the BAT token. It’s a donation. I don’t think anybody who bought the BAT token thought they were making a donation. So, I’ve been through that as well. You can issue assets on Liquid?

Adam Back: Yeah, exactly. Some users have, you know, got themselves a small amount of Liquid Bitcoin which is the fee currency on Liquid. To create an asset is just a special kind of transaction. So the fee for creating an asset is nominal, 10 cents, 20 cents, or something like that. So you can do that, and then you have a key as an asset issuer that allows that you have control over the issue. You have ownership of the initial issued assets, and then you can transfer those to people. And there’s an optional feature where you can make it like a one-shot issuance, so there’s a defined number of coins and that’s it. You don’t have the ability to make any more. And there’s an option where you have a second key, which is a re-issuance key which allows you to issue more. And in a conventional company stock scenario, people do that. They take another investment round and they issue more stock, which dilutes the existing stockholders. So there are reasons you might want to do that.

Peter McCormack: So, you could create securities on …

Adam Back: Yeah. Well, you can create assets now …

Peter McCormack: Can you create a shitcoin on …

Adam Back: I mean, it doesn’t have mining, but you can certainly create coins with arbitrary claims about what you’re going to do with the coin, what it’s used for, what software you’re going to build or what company it represents but … the ability to create test token is a separable question as to whether one of the exchanges would list it.

Adam Back: And there are some people who are working on security tokens. So, basically working with existing stock exchanges to issue tokens that represent regulated securities. So I think in those they would take steps to ensure that the customer is in some way approved to buy a security in this country.

Peter McCormack: Accredited, yeah.

Adam Back: Yes, like an accredited investor, or I guess a customer of an online brokerage or something like that. Not everybody might be familiar, but a lot of existing financial products are restricted in different countries because there are different rules. So it’s quite common in Europe that you’ll see, if you read the fine print of a structured product it’ll say, “Not for sale in the US,” or something and vice versa. And that’s because the tax rules are different, the ownership rules are different, there are different restrictions, and so for regulated securities you have those sorts of questions. I think they’re typically done in partnership with a stock exchange or something.

Peter McCormack: Okay. Just a couple more questions on that. We haven’t rattled through many of my questions, but we’ve covered a lot. So you can do private transactions within Liquid, Liquid or Elements, is it both?

Adam Back: Both. Yeah, actually you can compile the Elements code and put the right configuration into its configuration file and use it on Liquid. So it’s compatible. It’s kind of open-source. And Liquid itself, the full node, is open-source as well. So the difference is basically default configurations to auto-connect to the Liquid network with the right parameters.

Peter McCormack: Okay, so my first question is, if you can offer private transactions on Liquid, are you potentially going to be facing questions from regulators around KYC and AML? Is that something that you’re thinking about or worried about?

Adam Back: Actually, when we first introduced confidential transactions, we had a thesis that blockchains that are fully transparent like Bitcoin … there was a lot of financial institution interest in understanding blockchains and using them for different applications … that the complete transparency would be a problem for adoption. Our thesis was, they would see this and think, “That’s very interesting. We can derive value from it, but it’s so transparent and public, that we’re scared to use it because we would divulge our trading positions, how much we’re paying our suppliers, when we’re doing a deal.”

Adam Back: Some public markets have a public ticker, or a delayed publication, but other markets are not like that. And so we thought, “Okay, this is probably a necessary ingredient, confidential transactions, to see widespread adoption.” And when we did release it, I actually saw that. That was how they took it. They took it positively that, that was a needed thing, that they could have basically commercial confidentiality and still derive a value from a publicly auditable blockchain.

Adam Back: There’s that, and in the Liquid domain, the users are customers of exchanges. To take bitcoins out of Liquid, you basically have to do it with the exchange. There is a security reason for this, which is that the peg-outs go to a cold-wallet controlled by the exchanges. So each exchange has a cold-wallet, and the hardware module enforces that this payout goes to these cold-wallets. So it’s just an additional security mechanism. So the only way to peg-out is to do it via an exchange, and all the exchanges know who their customers are. Some of the participants are institutional traders, so their customer is themselves as well.

Peter McCormack: Right. And where do you personally stand on privacy with the main Bitcoin chain, and do we have a potential another civil war coming with regard to that?

Adam Back: I mean, that was my first reaction to Bitcoin was like, the privacy needs to be improved. And fungibility as well, which is a related concept. So I would be personally very interested to see confidential transactions and things like that make their way into Bitcoin as people get more confidence about them, and as the technical trade-offs are better understood. And the assurances efficiency improves, like the size. They’re a little bit big, like a couple kilobytes, so they’re maybe about 10 times bigger than a regular transaction.

Adam Back: But to me, if you could pay one cent for a clear text transaction, or 10 cents for a confidential transaction, I’ll take that confidential transaction. A confidential transaction is a more powerful transaction. So it’s quite common that people will break Bitcoin transactions up into multiple transactions. Basically, in search of privacy. Particularly value privacy. So if they’re doing cold-storage, and they have 10 bitcoins, they’ll kind of like, make 10 one bitcoin stashes, and then if they want to dip into it to buy something, they’ll know that the person can see this transaction, but it’s coming from one bitcoin not from 10. That means for some uses, there are actually lots of transactions. So if a confidential transaction can do that same guarantee, but with a single transaction, then it kind of displaces multiple transactions. And the fact that it’s bigger is not as painful as you might assume at first.

Adam Back: I think it’s pretty interesting to see what people think about that. Because Bitcoin generally only accepts opt-in changes that nobody has a clearly articulable reason why it would be a bad thing, or something like that. One of the interesting things is the breakdown of views might be along different lines. Like orthogonal to the arguments about scaling. Because I think that scaling from my point of view, is well-achieved by Lightning Layer 2, because that has much more scalability. I would say on-chain scaling has very bad scalability because the overhead grows beyond linearly, it grows like n squared. So that’s a bad protocol to be scaling, because you push things up by a hundred times, and now you have 10,000 times the overhead on that. At some point, it becomes untenable. Lightning kind of solves that.

Adam Back: For fungibility and privacy … I participated in a reddit discussion thread a few years ago, and I posed a question actually, that Trace Mayer had put, about what do people consider, like users and investors, what do they consider to be key differentiating properties of Bitcoin? Like, if Bitcoin lost this property, if they would be much less interested? And it seemed like it was almost universal agreement on privacy and fungibility being key amongst users and investors. Okay, it’s just a small group of them, because that’s the reddit community, but the Bitcoin reddit these days is almost a million users or something. But there may be people that would have concerns about it, right? Maybe they think it might decrease a little bit the chances of certain types of investor buying it, or certain regulations, or financial products built on top of it being approved. But I would argue that a more fungible private Bitcoin is more valuable to its core use-case. So yeah.

Peter McCormack: No, I agree. Okay. Conscious of time. Final question. So we’ve had 10 years. Where do you see Bitcoin going over the next 10 years? What would you like to see? And what do you think is going to be important for it? What do you think we might be talking about if we sat down in another 10 years’ time?

Adam Back: I’d like to see more fungibility and privacy make its way in to Bitcoin, and in each major release of Bitcoin reference and the protocol, BIPS, there are usually a few incremental privacy improvements. Like, Dandelion is one thing that’s happening at the moment, and Schnorr signatures have some advantages and the taproot and graftrootd has some advantages, so there’s some continuous incremental. But I’d like to see some bolder things too. Like confidential transactions or things with effects in that area.

Adam Back: In terms of the evolution on that, 10 years is quite a long time, maybe we’ll get closer to the top of the s-curve and see some more stability and wider adoption, and wider groups of people using Bitcoin for different reasons. It has a lot of interesting properties that people can use it for quite diverse reasons. And I think, much more usability, certainly ETF products don’t provide the same guarantees, but as a way to get investment exposure, they’re a lot simpler for many people. I had friends ask, “Okay, how can I buy it?” And calling their broker every year or so and asking them, “Is there any way I can buy it?”

Adam Back: Within some countries there are a few exchange traded note products and things like that, but you would assume the those kind of financial wrapper products would start to be available so that it becomes easier. And I think the other direction you’ll see is some of the online brokerages have added Bitcoin as an asset that you can buy through their platforms so that’s another direction. The retail offerings are becoming wider as well. Square for example, with their cash app you can buy Bitcoin and I hear their Bitcoin sales are growing. They’re a public company so their quarterly statistics are published.

Peter McCormack: Wow. Okay this has been everything I thought it would be. Very easy, great conversation, so many things I didn’t get into but that’s fine. You can just finish off by telling people how to keep an eye on what’s happening at Blockstream with Liquid and yourself, and who you want to hear from if you want to hear from anyone?

Adam Back: To keep up with what we’re doing there’s a blog on the Blockstream.com site. We post updates, and there are a lot of things in the pipeline other than the explorer and Liquid full nodes, so we’ll be putting out a version of the Green Address wallet with Liquid support which will make it much easier to manage Liquid assets. We’re also working with Trezor and Ledger on hardware wallet support, so that will improve the security and provide another option for handling Liquid funds.

Adam Back: For people who are interested to try things out, there is an IRC channel. The Bitcoin core community slack has an Elements channel, where people are talking about Elements and Liquid, and try it out. Read the guides. There are some power user how-to guides on ElementsProject.org which is the open-source site for Elements.

Adam Back: If you’re an exchange, or trader, or OTC proprietary trader, certainly get in contact with Blockstream. We’d be interested to connect you with an existing exchange, or potentially join as a member as the network grows.

Peter McCormack: Fantastic. Thank you for coming on, Adam.

Adam Back: Thank you.

Peter McCormack: That was amazing.