Crypto Twitter is Wrong: This is How Rollups *Really* Work

[Music] [Music] where are we there we go okay oh wait wait wait that's the that's a all right so um I've been kind of ill the last couple days uh sitting on the toilet so if I seem defeated and disheveled that's why um but this isn't the first time I was getting ill on this trip I've been in Bangkok for about a month or in Thailand um and the last time I was doing this I started tweeting and getting really mad at people on the internet and I realized that I'm not the only one that needs to get their together uh we better start agreeing on stuff or ethereum is cooked so that's the new talk I'm going to start this talk by telling you a little story um you know it's December 11th 1998 it's a mild day at Cape canaval Florida and some NASA smart cookies at Nasa are going to send a Orbiter over toor Mars right so they throw that thing on the on the rocket and then send it off wow yeah neat right great so it's a long tense journey to n Mars this whole thing takes like nine months $500 million a bunch of people's entire lives built into this thing goes all the way to Mars and then it's finally time for orbital insertion right so this is what's supposed to happen right rocket goes like this oh look it orbits Mars right that's what we expect yeah that's what we want but what actually happens is this this oh oh oh no it's way too low and then bam you know the whole thing falls apart uh the whole thing slams into Mars's atmosphere Falls to Pieces so why what happened what happened to this thing well the smart cookies at NASA went over to Lockheed and they said hey Lockheed you know what can you pass me that meter stick and lockheed's like yeah and Lockheed gives the meter stick to NASA and NASA's like hey Lockheed what this is a bleeping yard stick it turns out that Lockheed the whole time was building instruments that were returning data in US customary units why everyone would use as metric but the moral of this story right oopsie sorry the moral of the story is that shared definitions make or break projects if you don't agree on the words that we're saying you're never going to get anywhere and today while ethereum is facing more competition than ever we're wasting so much time talking past each other we're all saying the same things with different words and everyone hates each other so I asked the internet on Twitter what they think an L2 is and here are some of the responses I got an L2 is a chain that settles to an L1 an L2 is a cultural extension of ethereum like Cutlery a layer two is a function description not a specific design or form and I give up on the other definition let's just stop saying L2 it's a nightmare the reality is that we can't build the future of ethereum if we keep using these differing definitions we can't do it unless we have shared clear definitions shared clear definitions allow us to see the whole picture right and you can fill in the gaps if you're building a puzzle what do you do you build the frame first and then you fill in the gaps right now we're building ethereum by just putting puzzles in random pieces and so we better start writing a dictionary or we're going to end up like the Mars Orbiter so you know call it whatever you want but I think we need to build this I think we need to build the encyclopedia theoria and I think we need to get on it now um like any good dictionary the first word in any encyclopedia is artvark that's right and Arthur is an arvar I don't know what doesn't look like an arvar looks like a bear I don't think that they should have called him an arvar but whatever the next word is rollup now why roll up well when I ask people on Twitter what an L2 is nobody could agree but when I asked people what a rollup was I actually got surprisingly coherent answers and kind of the average that I got is this a rollup is just a normal blockchain that uses another blockchain for ordering and data availability all right that's that so let's kind of walk through it let's explain this right blockchain 101 what even is a blockchain right let's crack open ethereum what is a blockchain well it's composed of three main parts we have state that's the what the world of the blockchain looks like we have transactions that's how people change the blockchain and we have the state transition function which is the rules by which a transaction actually modifies the state we have two properties that are really important for any blockchain we have ordering right now let's say that wizard hat sends one eth to Timmy and Timmy sends one East to pretty hat person right that's fine we know that that works but if we swap the ordering and we say that the first transaction happens second and vice versa and Timmy tries to send one e a pretty hat person well if we look at the initial State we know that Timmy didn't have any eth and so this doesn't work right so ordering is really important no ordering no blockchain data availability is critical right what is that well it's really just a fancy way to say that you can actually download the transactions if you can't download the transactions and they fade away then the whole blockchain Fades away right if you if you can't execute the transactions because you don't have them in the first place you can't compute the state no transactions no block blockchain all right so blockchains use consensus mechanisms to establish ordering and data availability and there's an asterisk there but don't worry about it but it basically works so you know we know what a consensus mechanism is we have Bitcoin right so whoever has the most money and lights it on fire wins that's proof of work we have ethereum whoever has the most money wins that's great very human love that it's not plutocratic at all uh so these futuristic systems are complicated and costly and the reality is that they're very difficult and expensive to build in the first place I mean you try to build ethereum's proof of stake from scratch Good Luck then they're also challenging to maintain so even if you didn't build them in the first place just to run them is really hard and I think this is underappreciated but usually you need a token to reward participants right Bitcoin has Bitcoin eth has eth and the reality is that a lot of people for a lot of reasons don't want to make tokens cool so rollups solve this problem by Outsourcing consensus to another blockchain right this is all that a rollup really does let's explain how a rollup works by just giving an example so Timmy wants to send a transaction what does Timmy do he sticks the transaction into the M poool on the rollup just like you would in ethereum and then the validator or sometimes the block producer and we call it the sequencer sometimes uh takes that transaction and shoves it into a block with lots of other transactions and then it puts on its little Timmy hat and it grabs that block and it goes over to the ethereum mol where it tosses the block into an ethereum transaction puts the block into the ethereum men poool gets picked up by an ethereum block producer puts it into a block right this is a bridge but it gives you the basic idea validators come in they say okay sign off looks good take the block shove it into the ethereum blockchain now if you open that transaction back up there you go there's your rollup block right and now there might be older transactions that have older rollup blocks and older transactions that have older rollup blocks and because all of these blocks and the block data is just being shoved into ethereum transactions you get all of the the guarantees from ethereum about ordering and data availability about ethereum transactions right if you know that ethereum transactions are going to be ordered then you know if you put a rollup block into an ethereum transaction it'll be ordered too so to kind of recap that a rollup is just a normal blockchain that uses another blockchain for ordering and data availability right okay so if you've watched this talk and you kind of have some idea of what a rollup is then you might be asking where does the ZK or optimistic bit come in because we always talk about ZK Roll-Ups and optimistic rollups and and I never mention ZK or optimistic stuff at all in that description in order to understand this we first have to talk about bridges right what are bridges well you've probably used one before we kind of know what they do right they're applications they let you send tokens and data and stuff between different blockchains how do they actually work well all bridges basically work the same way you have two chains and then you stick two smart contracts one on each chain right these are two independent chains and someone comes by Timmy comes by and puts an eth or whatever into the smart contract on the first chain and then Timmy goes to the smart contract on the other chain and says money please and now the smart contract in the first chain needs to think well how am I actually going to verify what happened on op mainnet the problem is that this is a smart contract I mean if you were going to do this you would probably just run an OP main net node and it would love to do this as well you could just run a full op Main node inside of the smart contract but it's a smart contract it can't do that it's a resource constrained environment and we're not able to actually verify the full chain explicitly like this so instead the smart contract asks for a proof it asks for a succinct way to verify the state on the other chain and then Timmy comes up with a proof gives it to the roll up or to the uh gives it to the bridge smart contract and the bridge smart contract takes look at that proof verifies it according to some rules and then you know poops out some eth on the other side right so Timmy walks off and now you've completed your Bridge transaction this is generally the way that all bridges work whether it's a multisig proof or an optimistic proof or a ZK proof each time what's happening is that smart contract is using some Abridged metric to decide what's going on on the foreign chain so what I want you to get out of this is that proofs are things that Bridges use rollups don't use proofs Bridges use proofs right and this has some really weird implications I really want to want to have you internalize this because it sort of means that this word that we've been throwing around ZK rollup or optimistic rollup doesn't make a lot of sense because rollups use proofs or rollups sorry rollups don't use proofs Bridges use proofs right so if it's the bridge if ZK or optimistic is a descriptor of the bridge then why are we applying that descriptor to the rollup well where does this come from I think that there's a lot of historical context the answer is that basically rollups think that bridges are useful this is because it's useful to be able to pull economic activity from one chain to another and so rollup teams build these official Bridges and these Bridges because of the special relationship between a rollup and its parent chain can be these kind of special bridges that are more secure than Bridges between two arbitrary chains now the fact that it's the rollup teams that build these Bridges is just a coincidence of the fact that the rollup teams know the most about the thing but there's nothing really stopping any arbitrary person from building that bridge because it's official and because it is The Branding of the chain it becomes naturally popular and when people put more and more assets into that bridge it gets more and more influence over the social consensus of the L2 if the L2 wants to for work the bridge has to agree right or all of those assets on the bridge are not going to be worth anything on the fored Chain so and then of course at the end of the day the official Bridge has some sort of proof system and the result is that the rollup gets its name from That official Bridge all right so really to hammer at home one last time proofs are things that Bridges use rollups don't use proofs Bridges do so what what's the point of all this well well you know like I could I'm glad I'm disheveled because I can look really crazy when I'm saying this but essentially all this stuff about ZK Roll-Ups and optimistic Roll-Ups and there being a war and fighting between all these teams it's kind of fake news and and we're just creating this tension between teams for no good reason right and the other thing is that ZK and optimistic rollup is just really terribly limiting if you think this way you can't imagine new things like what if there's a chain with two massive Bridges at the same time and one's a ZK and one's an optimistic Bridge what is it a ZK rollup or an optimistic rollup who knows what if it's a chain with no bridge at all and then someone puts a bridge on that chain but the person who does that is just a random person what if there's a chain that posts blocks to two other blockchains or if there's a bridge with more than one proof system all these things are things that you can imagine if you're not constrained in this way so again at the end of the day Vicken Stein good quote limits of my language are the limits of my world and the reality is that our language just doesn't leave any room for novel constructions when people want to build something new they can't because they don't have the language to do it and so you're stuck with two really bad options and you can see this option number one is you make up a completely new term right so you first you get L1 L2 L3 optimistic role up ZK rollup plasma validium optimium volition Sovereign rollup like no one knows what any of this stuff is if I quizzed half of you you'd all be wrong right no one knows what this stuff is how am I supposed to convince a user to use my product if nobody knows what it is and the the other option which if you have less grupal you just do this you just co-opt an existing term you take a term that other people like like evm equivalence or you know rollup or L2 or whatever and you just decide that your chain is going to have that too and because we don't have good definitions everyone loses right every single person loses teams lose users lose the reality is that everyone's confused and so our language just isn't flexible enough for people to be able to build these things the end result of all this is that no one's working together you know how many times I've heard that quote the fact that there's an I think in front of that is insane what do you mean I think we're all just building the same CH same thing we should know if we're all building the same thing right it doesn't make any sense why are we doing this to ourselves and we're doing it because we don't have good shareed definitions so I was trying to figure out you know a couple weeks ago I'm I'm scaffolding these slides I'm I'm trying to figure out how to end this talk um and then this thing happens and it kind of fits perfectly with the rest of the talk booster coming in hot for booster [Applause] catch booster fds is [Music] saved andite 13 of those Raptor engines and this view is incredible right now I can't wait for us to hear the sonic boom Landing burn start up we can see those Chopsticks this is absolutely insane on first ever attemp we have successfully CAU the super heavy booster Gilla has caught the booster chip Ian power CL ninal Starship has enter those people those people share definitions all of them they all agree on the same thing and if you're ethereum today you can't do that ethereum can't land that and I know every single person wants to experience what those people experience but the reality is ethereum today can't do it but we could right we could catch boosters we could do it whatever but we have to start working together to create Shar definitions if we don't do this it's never going to happen so please join me try to help write the encyclopedia e theia we've got two definitions right we've got roll up in arvar that's a really good start um and thank you please help formalize stuff scan the QR code there's an empty GitHub repo I'll add arvar to this later on uh and I'll take any and all questions thank you very much much appreciated [Music] that was a great talk Calvin all right so we have some great questions over here let's go through the first one wow very interesting it's lasagna layer to I mean if your lasagna has two layers I don't think it's very good lasagna let's put it that way uh is a cant a croissant a rollup yeah why not what I mean it might as well be like that's you could ask someone on Twitter they' say yeah um can we see the rocket launch again I feel like it might take up too much time but I'll send you the video afterwards if you come to me all right so I'm going to mark this as answered what about croissan is that a rollup because we do have one vote over here um is a wait which one is a ciss rollup yes so cro is a rollup yeah um what are some other terms and Concepts that need to finding that's a really good question I think L2 is a hopeless term so let's not bother with that one at first but things like Bridge is a really easy thing to define the stages for rollups right stage zero stage one stage two I think those things can be defined very very well and that would help a lot of people um and kind of just I mean honestly at the end of the day more than defining new terms I'd like for the ecosystem to start throwing away terms and red finding things like Sovereign rollup or validium or whatever in terms of these simpler things that we can all agree on cool and when these questions guys when will I be bleaching my hair again I don't know I mean today I guess why not great I'll bleach my hair today and I'll whatever why not what are some other terms and Concepts any we talked about that rollups don't use proofs Bridges use proofs but rollups use Bridges right without a bridge what distinguishes a rollup from a foreign chain well all chains use Bridges right the fact that we have Bridges is not unique to rollups the unique thing about rollups is that it allows you to build a special type of bridge that has better security properties than if you just had two completely unrelated chains um but the fact that that's true doesn't mean that that bridge has to be built by the same people that built the rollup and it doesn't mean that you can only have one of these and you don't even have to have any of them if you don't want um since rollups Outsource consensus doesn't mean that decentralizing the rollup doesn't make sense uh this is kind of a contentious topic I would say that the correct answer here is that decentralizing the rollup means a different thing than it would on the layer one uh because you have most of your security prop properties even if you have a centralized you know block producer or centralized sequencer you don't lose liveness right because you can do this special thing between the rollup and the parent chain and you don't lose safety and so this is generally why doing stuff like decentralizing the sequencer has been relatively low on the priority list of a lot of R rollup teams because you have very good security properties and you don't really lose much except for this kind of short-term liveness now eventually short-term liveness will become the most critical part uh but usually focusing time and effort on the bridges and making those bridges robust takes up more time for people all right I guess we have a few more minutes for one more question um how does charting fit into this it's what I do on the toilet all day um how does Shing fit into this I don't know I this is such a confusing question I could spent a whole minute working on it um I'm going to skip that one perfect that's Mark all right we can leave it there yeah great all right great thank you [Applause] Kevin thank you [Applause]