WTF is the pessimistic proof | Devcon SEA

[Music] hi thank you MOS for the presentation and thank you everybody for coming my name is ignazi Ramos I work at polygon at the protocol team and today I will be presenting what the frog is the pessimistic proof but before going straight to the pessimistic proof let me give you a bit of context and nowaday one of the problems of of blockchain not being mainstream in my opinion is the the fragmentation there are a lot of good projects and they have to deploy in all the chains but the worst thing is that for the user experience this is like very very bad because they may want to use for one reason or another or or or another more than one chain Two Chains whatever number of chains so if they want to move assets from one chain to another one sometimes there are delays some sometimes it's difficult to track hike fees they have to wait a lot this is why um from polygon we propose the aggregation layer the agregation layer connects Sovereign chains together unifying liquidity users and state but with the feel of a single chain a multi-chain web that is better for the user experience better for Network effects and better for security we think for example like internet well where everything is built at the top top of the same protocol the TCP IP in the aggregation layer we will be aggregating chain in a unified bridge and they not have to be only evbm chain compatibles they can only be like what we call Sovereign chains for example a Solana whatever chain that they maintain like an state of their balances but with this system there is a problem what happen if one of these change is compromised what happen if one of these chains has a back that the bridge gets brain what will happen is that the other chains will be affected because of the insecurity of one of the other chains this is where we introduce the pessimistic proof the pessimistic proof has this name because it pessimistically thinks that any of the chains that are added in the aggregation layer can be vulnerable so it tries to secure this how does it do it the solution is to architect the aggregation layer in a way that assumes that every prer can be un sound the pessimistic proof guarantees that even if a PR for a particular chain is UN sound that Pro cannot drain more funds than are currently deposited on that chain in this way a sound issue cannot infect the rest of the ecosystem so this means that every time a chain wants to submit their Bridges to be Consolidated he will has to attach a proof proving that he has enough balance to execute those bridges the proving system that will um handle all of these the proof generation and the verification can be any of the advaned like General BMS like for example dis for example R zero or sp1 so let's go a bit deeper on the pessimistic proof now we will get a bit more Tech but it will be anyway very high yes very high level at least this is a aligning talk so it will be it will painless so we handle this the proof generation with the3 we have the local balance Tre the local Exit 3 and the nullifier threee the local balance Tre is the one that handles the balance of each one of the tokens in the network each one of the Le has the following information the origin network of the token the token address and the balance the origin Network and the token address completely define a token so this balance is the one that handles all the balances of the tokens in the CH in in one in each one of the chains another one is the local Exit 3 the local Exit 3 grow sequentially every time a bridge is created so in each one of the in each one of the leaves he has the information of a bridge a even yes and the third one is the nullifier tree the nullifier tree basically it's used for the um aggregation layer um to avoid the double spending I will explain it later and finally the step steps for computing this proof are this four well here it's a a very summarize oface first of all you apply the Bridge exit to all local exit three generating the new local exit three after that we apply the bridge exits and imported Bridges The Bridge exit are the one that are generated from my chain that want to transfer assets to other chains and the imported bridges are the ones that are generated in other chains I want to transfer assets to my chain so we compute them and we add them to the local balance Tre generating a new local balance tree finally we check the nullifiers we check that none of this bridge that we importing has already been computed or has already been Consolidated or spent and finally we check that none of the balances in the local balance three is lower than zero meaning that we can compute all these Bridges with the balances that we have in our chain so that will be anything from from my side thank you very much and if you have any question okay let's give a big round of applause for ignasi thank you ignasi for um for this presentation so these proofs apart from their name they're actually very fun apart from being pessimistic right we have time for for a few questions I will hit you with the red box which you talk at this is a microphone so please raise your hand if you have a question for ignasi it's not easy right yes please okay great presentation so my question is is this only for polygon networks or is supposed to work no no it will support any chain like um in the example there were like the cdks and the C which are polygon network but it can support like any chain that handles a balance of the state as I said it can even handle Solana fantastic it doesn't even have to be evm compatible great because it's one of the Chang is responsible of the state transition more yeah there please so um this sounds like a um security uh measure how does this help with like interoperability sorry what can you repat the last pessimistic proof sounds from yes it's 100% security security does it help does it simplify interoperability in any way like you say Solana could use pessimistic proofs like does does will does this help sending assets from one chain to the other that yes it helps in the way that you are sure that this chain has enough funds to be transferred so you the only thing you have to do is um verify that proof you don't have like to if in case now on the bridges wait that the transaction is finalized or in case of an optimistic roll up wait this days for the withdraw this will not be happening that make um the interoperability very fast okay thank you all that was it uh yes we have let's go like very I'll be here around anyway thank you okay well no that's it thank you ignasi thanks again