Transcript 0:00 [funky music] Welcome back to Bitcoin Season Two. 0:36 I'm Charlie Spears with Blockspace Media. Bitcoin Season Two is an era of new ideas on the oldest blockchain. It's the technical and the cultural smashed together. We feature new voices, new ideas, new topics. 0:51 Um, Bitcoin Season Two is produced by Blockspace Media, an independent B2B Bitcoin media company focused on the business of Bitcoin. 1:00 Make sure to check out our other shows, The Gwart Show, my personal favorite, and the Mining Pod. Hit us on our website, blockspace.media, and subscribe to our newsletter. 1:10 Also, anywhere podcasts are shown, YouTube, Spotify, Apple, you can find our content there. Again, make sure to subscribe to our newsletter. 1:18 Mondays and Fridays, we hit Bitcoin mining mergers, ordinals, Bitcoin technical discussion, soft fork proposals. We cover it all back to back in a short five to 10-minute read every Monday and Friday. 1:33 I'm joined today by Tyler Wittell and the pseudonymous Rindale of the Taproot Wizards. 1:39 We wanna talk about the process of creating the CatVM whitepaper, or whatever the new term for this monstrosity construction they've created. It created a lot of buzz this past week. So I'm gonna bring them up here. 1:54 Tyler and Rindale, welcome to Bitcoin Season Two. Hey, great to be here. Thanks for having us, Charlie. Yeah, so, um, I feel like, uh, you guys have really been leaning into your roles at Taproot Wizards. 2:08 You wear multiple, we might say, wizard hats. [laughs] Um, [laughs] you kind of act as, like, technical research and comms, and execute the projects. 2:19 Like, so to steal a line from Office Space, what would you say you guys actually do here at Taproot Wizards? Tyler, you wanna go first? Uh, sure. I would say I'm a sorcerer at Taproot Wizards. 2:35 I think that's the most pithy way to describe it. 2:38 Uh, by and large though, I, I would say I work a lot on our products, and I think the fun thing about being at Taproot Wizards is our products span everything from super technical things like CatVM, to producing a children's book that we can release- [laughs]... 2:55 to our community that hopefully explains that concept. And so what I really enjoy is getting to be really deep in the weeds one day, you know, chatting with Rindale about what is the construction of the system, 3:08 you know, how is it actually gonna work at a script level, and then also pop up and work with our community, you know, work on designing books like this, design the missions that we're doing. 3:20 And so it's a, it's a really, uh... I, I cannot imagine a better job to have. How about you, Rindale? Your s- your title is CTO, I believe, but what do you think of your role as? Yeah, it's, uh... 3:32 That's, that's the official title. On Twitter I write, um, Artificer, which, uh, is, like, a, a old school ordinals, uh, title. It used to be higher, uh, used in the protocol, but fewer people use that now. 3:46 It, it's, like, a wizard term for somebody that imbues items with magic, which, um, I think describes, you know, what I try to do. 3:55 So I, I kind of bounce between, uh, leading the technical execution of the, you know, products and services that we're building here at Taproot Wizards, and then also doing a lot of work on, uh, research and development for future, you know, products and services. 4:11 Um, we kind of do a mix of kind of pure R&D, trying to push Bitcoin forward, but something that I think separates us from a lot of other, uh, organizations in Bitcoin that do a lot of research is that we're doing it all in service of building, um, products that we, we actually want our customers to use. 4:33 And so, uh, we're, we're much more, uh, kind of practically oriented than I think a lot of other, uh, research organizations in Bitcoin. 4:42 And I, uh, try to lead the technical vision and execution of those two bodies of work. And a personal observation, both of those are actually classes in Dungeons and Dragons, both sorcerer and artificer. 4:59 So, um, I feel, I feel that a Taproot Wizards D&D group is right around the corner. Uh- [laughs] I'm an avid fantasy connoisseur, Charlie. Nice. I, I can't believe you're- So our fantasy role playing-... 5:12 just leaking alpha on this pod right now, Charlie. I can't believe you just did that. Yeah. Well, let me- Yeah. I know Casey actually has been trying out dungeon mastering. 5:21 So, uh, if we need another, um, if we need another, um, uh, you know, demon scare to sweep through the, the Bitcoin narrative, we can have our, uh... [laughs] Yeah, there's, there's not- We can recreate the '80s D&D. 5:34 Yeah, it, it's great to see that there's a little bit of satanic panic coming into the Bitcoin Season Two conversation. Uh, we could definitely use more of it. Yeah. 5:42 Yeah, it's on- only serves the, the wizard angle better. That's right. So okay, so you guys released this CatVM, I'm gonna use the term whitepaper until you correct me. Children's book. 5:52 What's the difference between- I'm gonna say children's book. Did not release a whitepaper. Gotcha. Children's book. 5:58 Like, what's the difference between a traditional whitepaper and this children's book, which we call CatVM-There and back again. 6:07 What, like, what are the material, uh, besides the, like, very obvious surface level stuff, what, like, what's different about this than a, than a traditional white paper? 6:16 I think one of the things we really tried to do in producing this children's book is give a lot of the motivation behind why CatVM is needed. 6:28 And so in a traditional white paper, I think what you would see is, one, it would be white and very boring, black and white. 6:36 Uh, and two, there would be a very quick motivation, and then it, it'd very quickly dive into the technical details of how this thing works. And I think we wanted to flip that script a little bit and say, 6:50 we, we kind of like, we get the technical details here, but what's really important here from a higher level is for people to understand what CatVM improves upon. 7:02 And so the point was to say, look, there's this history of bridges. They've failed for various reasons or don't work for various reasons. 7:09 CatVM will help solve that, and at a higher level, we're gonna need Opcat to do that. 7:15 And so I, I think it was really attempting to tell much more of a story, not just the story of young Rindale, but the story of Bitcoin's history of attempting to get, you know, off chain essentially, 7:30 and how can we tell that story in a way that makes sense to the average reader, the average Ordinals user, and then lace in some of these technical details for the people who are, 7:44 you know, wanting for that type of material. 7:48 Yeah, I, and I think on top of that, um, there's a pattern that we've seen a lot with, uh, a lot of the white papers that have come out in the last couple years, but also a lot of the protocol and technical designs that have come out, where people kind of start from a position of, you know, here's the tools that I have in the toolbox, what can I build with those? 8:10 And then, you know, now that I've built this thing, let me go and find demand for it. 8:17 And I think what we're really trying to do is, uh, you know, kind of start with where we see the demand already and, and where we see demand growing in Bitcoin, and then work backwards from there and say, "What are the systems that we need to build in order to meet that demand, and what's kind of the minimal set of things that we need in order to build those systems?" 8:40 So if, if you look at the structure of, uh, the CatVM children's story, it really is about, you know, saying, all right, there's all these people that want to get off chain. 8:52 They wanna be able to do other capabilities, um, either for, like, richer semantics or for privacy or for cost or for whatever reason, like, they wanna get off chain. Um, none of the existing solutions work. 9:06 The properties of a good solution would be, uh, that, like, you know, anybody can exit, that, um, it's, like, uh, not going to have prohibitive liquidity requirements on, like, the bridge operators, that it's not going to introduce, like, crazy risk for everybody who's using the bridge, like, et cetera. 9:26 And then we, we kind of said, all right, if you wanted to build that kind of system, like, how would you do that? 9:33 And our answer to that with sort of, like, the minimal, uh, set of changes against the Bitcoin that we have today is that you would enable Opcat, and you would, um, create a construction that we've, we've taken kind of, uh, a bunch of prior art, like, we're standing on the shoulders of giants, and we've, we've combined a bunch of constructions together using Opcat, and we are going to, uh, use that in order to build a bridge that we think people will actually use. 10:02 And so, you know, kind of instead of going from the, um, kind of starting with the details and then trying to work backwards to usage, we're really trying to start with the usage, work backwards the implementation details. 10:14 And then as Tyler said, we're trying to present that in a very accessible way, that people can read it and decide whether or not they're interested in this in the first place. 10:23 And then if they are excited about it, if they see the vision and the promise and they're excited by that, then they can dig into the technical details and start, you know, really trying to reason about, like, uh, how this thing is actually implemented. 10:37 Yeah, it's interesting because not a lot of, of similar works begin... 10:42 Like, a lot of, like, a, like a white paper might say, "There is this problem that exists, and here is a solution," whereas this children's book personalizes it, and it tells the story of you, Rindale, in fictional form- Whoa, ho- ho- hold on. 10:57 It's young Rindale. That's not me... young Rindale. It's a completely different person. Young Rindale. I'm sorry. Yeah. Yeah. 11:02 Okay, it's young, it's an alternative young Rindale in a fantasy world, and you desire to get off chain, and you explore the various options that we have and the pitfalls or lack of success or traction they've had. 11:16 So I kinda wanna pull back, and, uh, let's start with the, like, the process of you guys building this. I think this is one of the, one of my favorite, um, conversations too. 11:27 Like, h- like, how did you guys come up with the idea? How do you deliver this children's book, uh, to the world? Tyler, you also brought some visual de- demonstrations. Um, yeah, so what, how did this begin? Yeah. 11:45 So [laughs] it began with us waking up one morning. It, it, Rindale has come up with this amazing breakthrough, which is CatVM, and we're thinking about how to present it to the world. 11:59 And we get on our daily call, and Udi is like, "I had a dream last night, and in my dream, we wrote a children's book for this."And immediately all of us were like, "Yes, 12:11 this is, this is absolutely the way to present this." Um, it's just very on brand for us. It's very fun, and it will help us tell the story, which we actually think is a very important story. 12:21 So, uh, what happened is all of us kind of went into our little caves and worked on various story lines. And 12:30 I, I wanna share some of our early, early concept art with you today, 'cause I think it will be quite, quite fun. So- Yeah... let me, let me pull that up. Throw it up there. All right. So this, uh, 12:47 mess of things that we'll kind of poke around shows you how we got into this story. So I'll, I'll zoom in here, because this was really the... This was the first instantiation of, of this story. And 13:05 when, when we came up with this, this is, uh, y- you might notice some similarities to Bitland in, in my terrible drawings. But- Yeah, we have the same artist as Bitland here too. I, I know, I know. I'm still... 13:18 I'm sad that my, uh, little wizard never made it into to either of those. But, [laughs] uh, what you can see here is... 13:28 What we realized is the thing we're trying to s- tell is the story of getting on-chain to this off-chain, to layer two roll-up, whatever you wanna term this thing. 13:40 There are things we want to do with Bitcoin that we can't do today, and, and we are going to have to, you know, go off-chain to get there. And so 13:49 we went through and did some initial illustrations of kinda, "Okay, what have we tried so far?" You know, we've, we've tried Lightning. 13:58 I think Lightning has been promised for seven years, and it, it just, it, it, it hasn't really reached its potential. Um, and so, you know, w- I was like, "What should this be?" 14:07 Well, it's, it's the Lightning Wastelands, right? It's this thing, it was supposed to be off-chain. 14:13 You know, technically it is off-chain, but really you can't do anything you want to do there, and it doesn't work how you want it to work. Um, then we were... 14:24 Then I was like, "Okay, what, like, what is a multisig bridge?" Well, we all know about, like, the wormhole hacks and things like that and, and the perils of multisig bridges. 14:33 And so it felt only right that a multisig bridge was somehow collapsing, or you're getting sucked into a black hole or, or something like that in the middle of it. 14:44 And then I think BitVM has been the most recent thing that for the past six months has really captured the, the imagination and the hearts of our, our builders here. 14:54 But the more we looked into that, the more we were just like, "This, this seems like it, it, it's cool in concept, but it's always just gonna be imaginary. It's never gonna work in the real world." 15:04 And so, uh, you can see it's supported by these, uh, pre-signed Bitcoin transactions. Uh, yeah, for anyone from the Midwest, here's a guy who's asking you to hold his, uh, PSBT- Yeah [laughs]... 15:17 which was supposed to be, like, a, a Pabst Blue Ribbon. Um- Yeah... so I think, you know, our goal is to illustrate these as, as, like, fun and whimsical things that were happening. And then, you know, down here, 15:31 here's young Rhindale, and he's discovered the CatVM Bridge. It's, it, you know, it goes all the way across. It's very colorful, it's exciting. Uh, and as you can see, it's supported by a, a Merkle tree of, of cats. 15:45 And so what we really wanted to do was bake into these illustrations, you know, some truth about these systems, right? It, it's not just supposed to be... 15:58 If, if you really look at the drawings, the drawings aren't just, you know, fun and whimsical, but they, they actually do tell a story of what these various systems do and, and how they are designed. 16:13 And so that's, that's really w- was how we got started with this concept of, you know, off-chain, and chain, and, and bridging and, and all of that stuff. Yeah. 16:27 So, um, I kinda wanna go through, because I, I think you, you spend a very, like, appropriate amount of time introducing and walking page by page through the popular, um, known 16:44 techniques for accomplishing the off-chain bridge. And- Mm-hmm... 16:49 um, one of the first things you do, if I can share my screen, and if you're watching this, if you're listening to this on Spotify, definitely check out the YouTube. But you have... 16:59 You introduce this idea [laughs] of a bridge. Um, uh, and, uh, young Rhindale begins his journey in the multisig madlands. Yeah. And it's chaotic, and you have the risk of the bridge collapsing. Um, 17:16 and so you introduce this concept that we have to bridge in some capacity to another chain. And, um, you introduce multisig, pre-signed transactions, Lightning, before you get into the cat. 17:30 Can you just talk through just why the landscape, why the Bitcoin bridging landscape does rely on the infamous multisig setup here? Yeah. I'm... 17:45 So, like, th- the way that, you know, Bitcoin works right now is, um... So Bitcoin has a scripting system. 17:54 Like, when you make a Bitcoin transaction, if I go to send some Bitcoin to Charlie, um, I'm, I'm actually kind of sending my Bitcoin to a little program that he has the ability to satisfy. 18:09 So if you imagine Charlie has, like, a two of three multisig, like, what that actually means is-Um, the address for his coins are a little program that says, "Ah, here's three public keys. 18:23 If you show up with two signatures for them, then you can spend these coins." And there, there's like a couple different, um, you know, uh, mechanisms that we can put in those scripts. 18:34 So we can do signature checks, we can do what are called hash locks, where it's like, um, you know, here's the hash of a value. If you show up and you know the pre-image to that hash, then you can spend these coins. 18:46 So you can do signature checks, you can do hash locks, you can do time locks, so you know you can only spend this coin after some period of time has elapsed, and, um, that's kind of it. 18:57 Like, you can, you can combine those things together, you can do some basic arithmetic and a little bit of logic, but in general, you can put locks or conditions on your coins about, you know, who can spend them and when they can spend them. 19:13 But you can't really put any conditions on where your coins can be spent or, ah, sort of like how they can be spent. 19:21 And so if, if you wanna build a mechanism where, like, um, I, I lock up some coins in an, in a bridge or an address, which is really what this is, I, I send my coins to some address, and then I get my coins on another blockchain or a side chain or some payments layer or some, like, smart contract eCash mint or whatever, and I, you know, send those coins around, and then they're Tyler's coins now, and he goes to withdraw them, there's no way for the layer one Bitcoin nodes to be able to validate th-those transfers off chain. 20:01 Like, there's no way for the layer one Bitcoin node to know that Tyler is actually allowed to withdraw these coins. 20:08 So the way that we solve that problem today is either, um, we have effectively a big multisig, so I send my coins to this multisig, and then the operators of that multisig run some special software to validate the transfer rules of whatever this off-chain execution environment is, and then when Tyler goes to withdraw his coins, they validate like, "Yep, he's allowed to do this," and they just sign a transaction that sends the coins to Tyler. 20:38 So we're, we're just, like, asking, you know, some, some group of people or companies to just, you know, enforce validity checks for us and then just sign transactions. 20:49 That's, like, one approach, and then the other approach, which I think you're gonna get to in a minute, which is what happens with Lightning or BitVM or, um, other constructs, is we basically pre-sign a bunch of transactions ahead of time and then store these pre-signed transactions and broadcast them in the future if a certain set of conditions are met. 21:13 So it's kind of like we game out all the possible places that we think these coins should go in the future, collaboratively sign those transactions ahead of time, and then, you know, one party can, uh, uh, you know, um, broadcast the transaction in the future. 21:33 And, and, and, you know, the real challenge there is you have, like, a, a finite and known set of destinations for your coins ahead of time, which ends up leading to, like, liquidity issues, and it means that setup for this bridge ends up being very interactive because, like, everybody who has the keys has to trade around these pre-signed transactions ahead of time. 21:56 And so, um, you know, those, those characteristics mean that, that while these systems, you know, might work for something like a payment channel, it makes it really, really challenging to build, like, arbitrary bridges that don't have, um, some trade-off around either, like, liquidity or liveness or safety or something else. 22:16 Yeah, and yeah, you, uh... Let's, let's go back to this, uh, this idea of Lightning because, um, I think page, what is it, four of the storybook does summarize pretty succinctly, like, 22:31 that the Lightning bridge, these hash locks, they, they do create a very strong mechanism to move off chain, but it's a bridge to nowhere, as we describe. 22:43 Or maybe that's doing it a bit dirty, but you gotta, you gotta capture this idea in a children's book that's compelling to the reader. And, um, and for whatever reason, Lightning has not 22:57 delivered the user traction demand that, um, I think maybe a couple years ago a lot of people thought it would be. Um, you know, c-could you talk a little bit about just, uh, 23:14 the thought process behind, you know, uh, how we, uh, you know, where, what Lightning might be? Does this bridge to nowhere always lead to nowhere? Or, um, or where does that fit into the CatVM story? 23:33 Yeah. Uh, um, I, I, I think, you know, Lightning is, uh, it, it's, it's an incredibly useful system, and it's, it's, uh, technically, like, very impressive. I think the challenge here... 23:49 And, like, you know, we're, we're trying to make 23:52 a, a book that's accessible and kind of punchy and entertaining and kind of, like, gets the point across in a very succinct way, but, you know, I, I, I think, like, the, the kind of point behind, um, the, the messaging around Lightning is, you know, th-there was this idea that was really popular for a while I think it's still popular that we c- like anything you would ever need to do, you can do on Lightning. 24:18 So if you wanna do smart contracts, like, just do them on Lightning. If you wanna do, like, multi-party lending systems, like, you should build that on Lightning. 24:26 Like, anything that you can't do on layer one Bitcoin because it's too expensive or it's too slow or it's not expressive enough or whatever, like, just do it on Lightning.And, um, you know, Lightning is a really, really good system if you have, uh, participants who are online and they're willing to, uh, provision liquidity between each other, and you want them to be able to do, like, fast, low-cost payments between one another. 24:57 Lightning is a really amazing system, and the fact that you can, like, route Lightning payments across a bunch of those channels is, like, really cool. But, you know, 25:06 i-it's hard to do non-custodial Lightning on end user devices, um, both because currently Lightning requires a recipient to be off online in order to receive a payment. 25:18 So if you wanna do, like, a non-custodial, uh, Lightning phone wallet, then you've gotta, like, keep your phone out and awake when you're receiving a payment. 25:27 There's a bunch of people working on things to do, like offline Lightning receive, but that puts more, um, onus on having, like, a really capable Lightning service provider that, that, you know, handles that interactivity for you. 25:40 And then there's also just a lot of, like, liquidity and cost of capital issues that come with Lightning, 'cause in order to set up a Lightning channel, you have to lock up funds in order to, you know, send and receive payment. 25:53 And so if, if you want people to be able to just, like, quickly onboard to a system and start doing, uh, activity with it, that gets really difficult in, like, high-fee environments or when the cost of capital starts going up. 26:08 I think it's also, um, something where we don't really know how to do, like, multi-party Lightning in a safe and scalable way yet. 26:15 And so, you know, Lightning is, is kind of useful and, and good at a certain set of things that it's really, really good at, but it's, it's not the case that Lightning's gonna be a panacea for all L2s to do everything that they need to do. 26:28 And, and that's kind of the point that we were trying to get across, where, you know, uh, like, th-this is not gonna be the bridge to, to everything off chain. Yeah. 26:39 If I were to summarize it briefly, I'd say Lightning's promise was payments for Bitcoin, and I think what we've seen over the past six, seven years is that payments for Bitcoin is not a, a high demand use case as of today. 26:52 And so while Lightning gets you off chain, um, unfortunately payments for Bitcoin is just not, uh, a use case that is demanded in the real world right now. 27:06 And so, you know, had that been the case when Lightning was released, I think we would see potentially a lot more Lightning adoption, and we would've moved... 27:14 We would've worked through some of these technical issues and, and a lot of the other things. 27:19 But by and large, you know, Lightning offers payments, and as far as we've seen today, payments are not the thing people want to do with Bitcoin, by and large. 27:34 And payments have their own challenges and pitfalls and perhaps ceilings to, like, how feasible we can scale these payments with Lightning. And then the last before we get to young Reindel disillusioned 27:48 wa- wandering into the, the Merkle forest, we have the, um, the L2 village, uh, propelled and attracting, uh, venture capital and can be a bit of a Rube Goldberg machine. 28:04 Now, I know you guys have been-- this has been a, this own narrative the past few weeks, but just kinda describe to me some of the, again, the challenges we face with, with new proposals or the uncertainty that things like BitVM bring. 28:20 Like, it, it itself may not be this panacea or solution to creating these strong, compelling, robust bridges. Yeah. I think BitVM is a, a really cool design. 28:36 Um, it's just a cool thing. I don't wanna call it a bridge 'cause it's not, you know, uh, it, it is- Well, yeah... just a design of a system. 28:44 Um, and what BitVM does is it lets you encumber coins to some arbitrary computation that can be resolved on Bitcoin. And, and that's, that's really neat. 28:56 Like, that is something we did not think we could do before, and when Robin put out this phenomenal paper, it became clear that, you know, you could do this, um, starting by building a program from NAND gates on Bitcoin and up till where we are today. 29:13 But BitVM faces the same issue that Reindel talked about with Lightning of these liquidity requirements in a, in a slightly different way, in that if you want to use BitVM to get off chain to, you know... 29:28 If you wanna use it as a bridge, then the way it works is that you have to rely on, um, bridge operators fronting your payment off, you know, if you wanna go back from the, the off chain to Bitcoin, you have to rely on bridge operators fronting your payment. 29:47 And then only after they've done that can they go back to the BitVM bridge and say, "Hey, look, I've made all the payments that were requested. I would like to take the money out of the bridge I'm owed now." And I think 30:00 this is totally fine in small use cases, but if you want to design a, a second layer that is to scale Bitcoin, you ideally wanna see a lot of volume going into that. You wanna see a lot of use going into that. 30:13 And the larger these BitVM bridges get, the higher the, the capital requirements are essentially to safely operate these things. 30:22 So, you know, if we had a bridge the size of Arbitrum with seventeen billion dollars locked in it and people wanted to take a billion dollars out, 30:30 the bridge operator is required to first go and find a credit line for a billion dollars, make all those payments, and only after they've done that can they go back.To the actual bridge contract and say, "I'd like to take my, you know, my funds out of the bridge now. 30:47 Uh, look, I've made all the payments." And so, um, at the end of the day, I think BitVM is a very cool construct, but unfortunately it doesn't really solve getting, you know, mass user adoption off chain. And so 31:04 here is young Rhindell fearing that the citizens of the Isle of Chain will never safely reach off chain. He's explored all that the Isle of Chain has to offer, 31:17 and he grows weary from his journey, and he spies and takes refuge in the Merkle Tree Forest. And the story does a kind of a switch up, and it becomes, uh... and, and introduces, uh, a quantum cat. 31:33 So talk me through, um, uh, I mean, you could either explain what a Merkle tree or, or how, how you, how you chose to introduce this concept, um, or, uh, where does young Rhindell, uh, go from here? 31:51 Rhindell, do you wanna talk about your journey through the, the... Not your journey, young Rhindell's journey. It's not me, it's young Rhindell. Not you, it's young Rhindell. Yeah. Yeah. 31:59 So- It's like if my name were Charlie and his name were Charlie, we would not be the same person. Yeah. You guys are... Like, not all Charlies are the same person. So, um, yeah. So, you know, Merkle trees 32:11 are an incredibly useful data structure in, uh, you know, blockchain systems. They're used all over the place in kind of cryptocurrency systems. Um, the idea is that, uh, 32:26 you know, you can have a single hash, so like a 32 byte hash, that commits to a set of items, and then later on you can show up with one of those items and this thing called a, uh, either a Merkle inclusion proof or a Merkle authentication path, and it proves that that item was included in the set that you previously committed to. 32:56 So this is used all over the place. So for example, um, in a Bitcoin block header, one of the items, one of the fields in there is like a Merkle commitment to all the transactions in the block. 33:08 And so that commits to all the transactions that were confirmed in that block. 33:12 Uh, given, you know, one transaction, you can prove that the, the proof of work from that block header covers it, and if, if anybody kind of like changes the set of transactions, it, it breaks the Merkle proof. 33:24 So, um, th- these things are used all over the place because you can, you know, provide a, a little bit of data that lets you prove in the future that one of many, many items were included there. And, um, 33:40 if we have Op_Cat, we can actually validate Merkle proofs in Bitcoin scripts. 33:46 So going back to what we were talking about earlier, where you can do kind of hash locks and, um, signature checks and time locks, we would also be able to say, all right, uh, you know, when I put my coins into this UTXO or into this script, I'm committing to some set of items, and then later on at spend time, I have to show up with one of those items and, and prove that it's like one of the ones in the original set. 34:12 That's like just a generically useful construct in, in Bitcoin. Later on, we use it to build up CatVM, and so we needed to introduce this idea in like a fun and whimsical way. 34:24 And so the way that we did that is we have, uh, the protagonist, young Rhindell, like work his way through this complicated forest, and the cat shows him this path, and then later on he gets to remember like, oh, the cat taught me that. 34:38 And, uh, the, the path through the Merkle forest leads him to this library, and then in the library he finds, uh, some wisdom from some, some previous, uh, sorcerers or previous wizards. An arch, archmage. Yeah. 34:52 Andrew- So the first one is Archmage Poelstra... Archmage Poelstra. This is a, a nod to Andrew Poelstra, who's the head of research at Blockstream. Um, he put out a blog post, a... 35:00 or a couple blog posts a couple years ago called Sh- Cat and Schnorr Tricks. 35:04 And, um, this was this really brilliant observation that, um, if you pick particular values for the public key and the public nonce commitment in a Schnorr signature, then, uh, the value of your Schnorr signature is, um, kind of the hash of a bunch of parts of your transaction plus the number one. 35:28 And so, uh, what that lets you do is it lets you, uh, if you have Op_Cat and if you have Schnorr, Schnorr signatures, then it lets you get, um, parts of the transaction onto the stack, and then you can use Bitcoin's script to make assertions about it. 35:44 So earlier I was saying you can really only do like hash locks, time locks, and signature checks. 35:49 If you have Op_Cat and you have Schnorr signatures, then by building this special signature, you can now like look at the outputs of your transaction. 35:59 You can look at where the money's going, how many destinations there are, what those destination addresses are, where the money came from. 36:08 You, you get a lot more visibility into the transaction, and you can start making assertions over it. 36:15 And you embed, you sneak a, you put a sneaky little link to the Taper Wizards GitHub in here describing just a prototype- Mm-hmm... that I believe old Rhindell built, um, which, uh, prototypes a vault using Cat. Yeah. 36:31 Yeah. So this was, um, this was a really nice, uh, I think it's nice. It's a nice prototype of a vault. 36:38 So a vault is this construction where, um, youPut some coins into this, like, vault UTXO, and then when you wanna spend them you don't just send them to, to their final destination. 36:50 Instead, um, you have to go through this, like, unvaulting step where you say, "All right. I want to send... You know, I've got 10 Bitcoin in this UTXO. I wanna send one Bitcoin to Charlie." 37:02 Um, I don't just send them immediately to Charlie. Instead, I start this, like, pending withdrawal step, and my coins have to sit there for, like, a week, and then after a week, um, they can, they can go to Charlie. 37:17 And the idea is that in the happy path it kind of takes, you know, a week or a month or whatever you program, uh, your coins to be withdrawn from the vault. 37:26 But imagine somebody gets my, my keys, and they try to unvault my coins. 37:31 I might get a push notification on my phone that says, "Hey, your coins are being unvaulted," and I say, "No, that wasn't me," and I go and I can push a button, and it'll, um, kind of cancel the withdrawal by sending my coins either back to the vault or to a new set of, uh, to a new set of keys. 37:46 So or a different set of keys. 37:48 So, you know, um, a lot of custodial exchanges will support address whitelisting where you say, like, "These are the places that I want my coins to go when I withdraw them," and if I wanna send my coins anywhere else, uh, it takes, you know, seven days to add a new address. 38:03 You can do that today if you have, like, a trusted custodial exchange, but it'd be really great to be able to have that kind of logic enforced by Bitcoin nodes. 38:13 So a vault is a way using covenants to, um, you know, build that kind of construction where you have reactive security, where if somebody tries to steal your money, you can react after the fact and actually get it back. 38:26 And that concept of, you know, I've got my coins, and I can kind of optimistically withdraw them, and then if it's an invalid withdrawal, then there's a way of challenging that and, and kind of canceling it, is, is actually really similar to what we want in a bridge. 38:42 What we would love to be able to do in a bridge is say, "All right. 38:45 We've got my coins bridged to this, you know, payment system or this smart contract system or this auction house or whatever," and when I'm withdrawing coins a- back across the bridge, 38:57 if, if I'm being honest, then that just works, but if I'm trying to steal somebody else's coins, then there's a way for them to cancel that and keep me from taking the money. So young Reindel, uh, in the library, uh, 39:15 working his way through the book of spell, the books of spells, sees Archmage Pulstra. Then, um, he finds M-A-T-T, a spell by Salvatore, and I know you just kind of already, uh, touched on this, Reindel, but, um, w- 39:35 that leads us into the actual proposal for CatVM, um, here on page 11, where, uh, 39:50 you can start actually constructing these permissionless bridges. Can you talk me through what CatVM actually is, again, here in the kind of, like, revelatory moment for young Reindel? Yeah. 40:05 So there's this idea called MAT, which is, um, kind of the, uh, pr- uh, intellectual precursor to both CatVM and BitVM, and it's this idea that you can take an arbitrary off-chain program and encumber Bitcoin with, like, the, the result of that program, right? 40:26 So it has this kind of optimistic withdrawal path where you say, uh, "My coins can only be withdrawn if, if, uh, the result of this, like, off-chain program is, is valid," and in the happy path you just take the coins out, but there's kind of a holding period, and anybody can show up during that holding period and say, "No, uh, the result of this off-chain program is invalid, so you shouldn't take these coins." 40:53 Um, that's kind of the same shape as the vault that we just talked about, right? 40:57 But the difference is instead of just saying, "No, I don't want my money to leave," you say, "No, here's a fraud proof that you're not allowed to take those coins." 41:06 And so MAT was this idea of how you can build that kind of behavior using Cat plus, um, another covenant called Check Contract Verify, and the revelation that young Reindel has here in the library deep in the Merkle forest is that, um, the, the Cat and Schnorr tricks and the, uh, Merkle path verification that, that he learned from the Quantum Cat, that these two things on their own are powerful enough to build this, this whole MAT mechanism. 41:41 So if you combine these, these three ideas, what you have is a generic mechanism where you can say, um, "I wanna send my coins to an address that, uh, in order for them to be withdrawn, they have to go through this kind of time delayed holding period," and during that holding period, somebody can show up, and if they can, you know, uh, put me through this challenge response game where we adjudicate whether or not this arbitrary off-chain computation was valid, and if, if I lose, then the coins kind of go back to where they were, and if I win, then I get to take the coins. 42:22 And that mechanism is, you know, powerful enough and expressive enough for us to start building bridges to off-chain systems, whether those are other blockchains or side chains or things that we haven't thought of yet, where, um, y- you can have, like, arbitrary expressiveness in those systems and still have-A safe way for people to get their coins back onto layer one Bitcoin and do it in a way where you're not trusting, um, like, a centralized bridge operator to provide liquidity. 42:57 You're not trusting a bunch of multisig custodians to, like, honestly sign for a thing, um, and, and you don't have the, the kind of, um, complexity and issues that we talked about earlier. Yeah. And we get to then 43:12 my favorite page of the whole book, which is- It's the best page. It's the best page, and, ah, 43:22 in particular, shout out to, uh, Teresa Lieb, ah, for the art 'cause I think this is one of the more hopeful pages, ah, I've ever seen, and one of the more exciting ones, complete with the, ah, rainbow price chart in the background. 43:39 Um, and I see, I see a lot of the characters here crossing the Merkle tree bridge, and they're talking about things which excite me and, and kind of remind me even of a lot of the old, like, 43:55 Bitcoin experimentation that I, that I knew and grew to love, ah, early on. And you introduce some of these words, which I don't think... I don't really hear many Bitcoiners talking about, such as SNARKs or Plasma Cash. 44:10 Um, or even just this idea of trustlessly swapping coins. Like, there's always been a trustful component of that in Bitcoin, and, um, I was gonna kind of y- ask you guys, like, do you have, um... 44:25 what is your favorite, may I say, pet unlock that Cat, um, could enable? Oh, man. 44:36 Uh, I think SNARKs would be just really, really cool if we could do SNARKs or STARKs on, on Bitcoin. Um, 44:46 but I, I think for the, the Ordinals crowd, I, I think one of the coolest things is this idea of trustlessly swapping coins. 44:54 So I think there's a lot of issues in Ordinals today with the user experience, like, just bringing it back up to that level that people don't like. For instance, 45:05 a lot of people don't enjoy that if they buy something on Magic Eden, that there's 10 minutes during which anyone could snipe their Ordinal out of the mempool and, and pay a higher fee and run off with it. 45:19 Um, or that if we do an auction today, you either have some type of trusted mechanism where you have to pre-deposit things in a certain address, or you have to do a descending price auction. 45:31 And so I'm, I'm excited to see what we can do to just improve the overall Ordinals user experience with something like CatVM, where we can have Magic Eden build our marketplace on top of this, and when you click the buy button, it's, you know, it's yours. 45:49 You don't have to worry about who's gonna pay a higher fee in the middle. Where artists can come and say, "I wanna auction off my work, and here's an ascending price auction. 45:58 Pay in what you're willing to pay," and at the end, we distribute all the coins back to everyone who didn't win. And all you have to do is trust that the system works the way it's going to. 46:07 And so I think those types of products and things are really exciting and definitely things that we wanna explore further with CatVM. How about you, Rhindell? 46:19 What, uh, what's, uh, what's young Rhindell's dream, uh, unlock for CatVM here? Um, I think it's, it's a couple things. 46:31 So on, like, the L1 side, I think even without CatVM, just, like, the bridge constructs, or I'm sorry, the, the vault constructs getting really bulletproof is gonna be really valuable to just, like, hold your Bitcoin with. 46:45 Um, on the, on the CatVM stuff specifically, um, you know, what Tyler said I think is really interesting. I think there's, like, a lot of fun, 46:58 uh, valuable things that people wanna be able to do with, you know, Ordinals and other kind of on-Bitcoin assets that are just very difficult or, um, hard or impossible to do today. I think that stuff's really exciting. 47:13 I think also just, like, um, you know, as much as there's not demand for, you know, a lot of Bitcoin payments now, it would be really nice to have a payments layer where, you know, you install an app, and you get an address, and you can, like, post that address on Twitter, GitHub, you know, whatever, and then turn off your phone, and people could just send you money, and you don't have to worry [chuckles] 47:44 about, like, liquidity or channels or your phone coming online or, like, any of that stuff, and you can just, like, receive money, and it's private, right? 47:52 It's, like, uh, you don't have to worry about in 15 years if some, like, Chainalysis, uh, breakthrough is gonna uncover the linkage between all your payments. 48:01 Like, having just fast, cheap, offline capable, uh, not liquidity constrained payment layer for Bitcoin I think would just be really fantastic. 48:11 I, I don't know when there's gonna be demand for that, but, um, having a plausible path to be able to build it at some point in the future I think would be really exciting. 48:21 Um, and, you know, if, if that demand never actually materializes, those kinds of capabilities are still gonna be really useful for things like Ordinals trading and, um, you know, borrowing against your assets and, and doing all, all kinds of other financial activity on Bitcoin. 48:40 Yeah. You know what? I... 48:42 my, my takeaway from the, this last page, which shows all the, you know, suggests and floats some of the cool things you can do with Cat is that-There is something for everyone, whether you're the, the privacy, uh, as the-- your number one goal for Bitcoin. 49:01 Like, that's a very core component to a lot of old school and new school Bitcoin folks. 49:08 To whether you're the DGen who, uh, just wants to not get sniped for ordinals, or whether you're like the Eth tech, tech head who really likes SNARKs. Like, these are all, um... 49:20 Each of these has its own compelling unlock and use case for Cat. Um, if I'm not mistaken, like, there's still very little actual implementation of Cat to date. 49:33 Like, I think you-- the-- your prototype, Rindale, is one of the only ones, um, that I'm aware of. 49:42 Like, w- do you think that the, the Cat-- that one of just the, the missing components here is that people just need to workshop actual, actual, like, implementing Cat? 49:53 Do you think there's more things to even just be discovered, like, beyond simply just the theoretical that Pulstro wrote? Um, like, w- 50:03 are there maybe things that Cat-- that we haven't even identified, even amongst the handful of people even thinking and ideating on Cat? Is like, is there even more to this than just the children's storybook here? 50:17 Uh, that's a good question. I think, you know, I, I think it's fair to say that, like, we've been pushing the bounds on Cat research. 50:28 Um, there's, you know, some other folks that have been doing some experiments with Cat in other places like on Liquid, but I think, I think we've been really kind of pushing the envelope on Cat on Bitcoin. 50:39 Like, Cat, Cat on its own without other assumptions for things that just aren't gonna be on Bitcoin. 50:44 Um, I think one of the results of that research is we have a better idea of the kinds of things that Cat can enable technically. 50:56 Now, the, the thing that's, like, kind of always unknown is what the, you know, economic and market result of those things are gonna be, right? 51:05 Like, um, I, I, I think we spend a lot of time thinking about what are the systems that are more likely to gain traction and adoption and, and what things are less likely. 51:16 And, you know, that opinion is informed by watching fifteen years of development on Bitcoin and, like, multiple years of development in other ecosystems. 51:26 Um, you know, it, it's-- there was a little bit of a meme for a while that if we got op_cat, it would enable everything, and, and that's just not true. Like, Cat enables a very specific set of new capabilities in script. 51:40 You know, what people build with those is the, the thing that's, like, exciting and, and where we're gonna see more development. 51:48 Um, there are some more technical directions where it, it would be great to see more experimentation with Cat, and we're, we're certainly leading some of that, and we would encourage other people to experiment as well. 52:00 Like, you know, we talked about Merkle-ized, uh, lookup earlier. 52:04 There's a lot of cool ideas of, like, all right, what other things can we put into a Merkle tree, and, and how do we use that to emulate other opcodes or to, like, add other Bitcoin scripting capabilities? 52:15 So I, I don't know. I, I, I guess to summarize, I'd say, um, the, the future's kind of somewhere in the middle. 52:22 Like, it's, it's not the case that we know everything that people are gonna do with Cat, but it's also not the case that Cat, you know, blows open the doors to, um, unbounded computation on layer one. 52:35 It lets us encumber coins with, you know, uh, arbitrary off-chain computation, but it doesn't, like, turn Bitcoin into a different system than it is today. Yeah. So, 52:51 uh, I feel that kinda-- that, that, that resolves the, the Cat storybook as it is, um, so far. Um, how do you... You know, it's been a w- a week and a half, two weeks, I think, since you guys dropped this. 53:07 Um, like, looking back, how do you think it's been received? Do you think it advanced your own story of the Taproot Wizards well? Um, reflections on your first, uh, storybook, uh, uh, writing experience here. 53:27 Yeah. I, I think I've been really happy with how it's been perceived and received by the community. Um, 53:35 I think it's really gotten the point across that w- what we can do with Cat is these permissionless bridges where if you're on the L2 and you wanna come back, 53:45 you can do it, and you're in charge of your own destiny, and I think that's just something really important for us as system designers who want to design, you know, the, the scaling layer that Bitcoin deserves, and I think Cat is gonna allow us to do just that. 54:01 And so it's been really amazing to see the reception around that. I think that the technical community has been very excited as well, and I, I know Rindale, I'll let him speak more to that. 54:12 But it's, it's been really good to see people 54:17 who are more in the weeds technically look at our children's book and say, "Oh, I, I see what you're saying here, and actually this, this gives us really cool new primitives." 54:28 And so by and large, I think, um, it's been a, a, a smashing success as far, as far as I can tell. Uh, I look forward to getting a, a hard copy to distribute to my, uh, future children. Yeah, same. 54:42 Um, I think my, my only regret is, uh, I wish we would put page numbers on the pages. But otherwise it's been a smashing success. Um, I, I love it. 54:53 Uh, we, we've gotten a lot of feedback from people that, um-You know, despite us not calling this a white paper and, and saying over and over again that it's a children's story, a lot of people perceive this as a white paper, and have been telling us that this is like the first white paper that they have read in a long time, and that they enjoyed reading, and that they actually wanted to share with people. 55:15 Um, I, I think that there's, uh... 55:18 You know, a, a lot of times when you're putting out a new idea, your goal should be to, to make that idea accessible and understandable to, to the people that you wanna communicate with. 55:30 And sometimes I think people, um, spend a lot of time trying to, to dress up their ideas and, and make them like really formal, 'cause they think that's important. 55:39 And at the end of the day, like the, the goal here is that, you know, we think that we can build, uh, really, really useful systems that people will actually use if we have Opcat, and we want as many people to understand that idea as possible. 55:55 And, you know, some percentage of those people are gonna be really curious about it and are gonna wanna dig into the details, and the details matter, but, um, you know, we, we, we should be making, you know, new ideas and new breakthroughs in Bitcoin as accessible to as many people as possible so that, so that people can, can decide whether or not to engage with it. 56:14 So yeah, I'm, I'm thrilled with the book. Um, you know, who, who knows what wild and wacky new format we're gonna do next, but I, I think it'll be a lot of fun. 56:26 And yeah, and Reindel, you know, unlike, unlike the Quantum Cats, this is a PDF, so we can in fact update that AWS pointer- [laughs]... to point with page numbers. That's, that's true. Yeah, you know, it's really funny. 56:39 Uh, our, our production process for this was very different, 'cause like with Quantum Cats, we had to make sure that everything was absolutely perfect before we pushed anything. 56:50 And with this it's like, "Oh yeah, we'll, we'll update the PDF later if we need to," which was like not a thing that we're used to at Taproot Wizards. 56:58 Well, take some of the initial, uh, unwavering execution risk off your shoulders, Reindel. Um, and maybe, maybe we, maybe, uh, this will spawn an era where white papers aren't so stodgy and boring and uptight. 57:11 Maybe, uh, we'll look back and say this is the, the new white paper, and perhaps, uh, perhaps we'll see non-technical artists credited on very technical white papers. 57:23 That would be a really cool very Bitcoin Season 2 thing to happen. 57:27 Um, I wanna thank you guys so much, Tyler, Reindel, and the broader Taproot Wizards team who worked on this for joining me and explaining this arcane concept to, uh, me. Uh, thanks so much, guys. Thanks, Charlie. 57:44 Yeah, thanks for having us. Thanks for joining Bitcoin Season 2. Make sure to check out, uh, uh, Bitcoin Season 2 streamed and on podcast form wherever you listen to content. 57:58 Hit up blockspace.media, our website, and subscribe to the newsletter. Thank you very much.
