 So, good morning everyone. Welcome to hyperlogical form. I think this is a great way to start off to kick off hyperlogical form, because interoperability is a really hot topic nowadays. My name is Rafael Balsher. I'm a PhD student at Technical Lisboa and researcher at Inesky Day. And I'll be talking a bit about interoperability. What is it? What are the current solutions available? And how can you get started working on this topic? As a side note, if you're interested into interoperability, I encourage you to also attend to other interoperability talks, specifically those from Shingo and Peter, from Hyperlogic Actors, from Pandit, from IBM, and also from Serra, that's going to present our recent work on interoperability. All right, so this is the outline. First, introducing interoperability, then introducing the current solution categories that tackle this problem. I'll introduce some examples, give some feature directions, and conclude this presentation. This presentation is based on a study conducted by my colleagues from Technical Lisboa and I. It's a survey on blockchain interoperability. It's accessible through that QR code that has been recently published at ACM Computing Service. So first of all, if we want a blockchain use case, we need to answer some questions. There's more than one entity needs to contribute data. That's typically the first question. If the answer is no, then we do not need a blockchain because we only have one entity participating in the system. The records need to be updated from time to time. If the answer is no, then we should instead use a database because blockchains typically provide immutability. It is actually not completely true because there are some recent advances in redactable blockchains, which means that you can change the content of a blockchain without compromising its integrity. This is for helping out with the issues around data privacy and protection. And if you feel all these conditions, you might have a useful blockchain use case. You need to check lots of conditions. So it tends to be a niche technology that it's very good to solve a certain subset of problems. And these technologies spread across hundreds of blockchains, which can answer to its specific use cases. That's valued at $260 billion. It was the market cap of cryptocurrencies a while ago. But we can see that there is a huge heterogeneity and a huge diversity of blockchains that come with a lot of value. What does this cause? The fact that there is fragmentation, that there are isolated silos of data and value that uses vendor locking and the risk of a blockchain deemed old, insecure, a bug, and the lack of standards makes it risky for enterprises to invest because it's a considerable investment. This is a light to the fact that there are no data migration tools available, or at least general-purpose blockchain migrators makes blockchain a difficult, reasonable investment, at first in first sight. And then comes the integration problem. If we want to connect our blockchain to another number of blockchains, the complexity rises quite quickly. So if we're connecting every pair of blockchains, if we have 10 ledgers, then we have about 15 integration scenarios, but you can see that that number grows quite quickly. And this is all part of the process. In the Gardner's Hype Cycle, we are probably located, we as in blockchain technology, in the slope of enlightenment. So it's where people start to understand that blockchain is not going to solve all problems that we have, but instead it's very good at solving certain problems. And this maturing process, where people start to understand this and where people start to explore the real use cases, are done in the slope of enlightenment. This is also where standards and interoperability is established. So the technology can reach its mass adoption and reach the plateau of productivity. The study is called a survey on blockchain interoperability past, present, and future trends. It was done in a quite long span and it was updated quite recently. In this survey, we analyzed about 300 documents where we analyzed systematically about 70 solutions dedicated to interoperability. Again, you can access this paper on the QR code. One of the first findings was that research trends on interoperability are rising. This is not a big surprise because interoperability is and will be more and more important as more and more blockings exist and as more and more diversity of blockings exist. So the number of search results on Google scholars, so this is regarding academic work mostly, is rising quite rapidly throughout the years. Our survey tries to cover most aspects related to interoperability, right? So there are some work on systemizing knowledge about interoperability. You can see some of the surveys there, but they are mostly focused on public connectors. That's what we call PC here in this table. We also explore blockchain of blockchain solutions and hybrid connectors that I'm going to explain a bit later as well as architecture for blockchain interoperability, these standards cross chain, cross category actually analysis of these different categories, some use cases and research directions. So we try to be generating an holistic view of this field. This is the main contribution of our work. We divide the solutions for watching interoperability into three categories. The green ones are public connectors. So they essentially connect public blockchains across each other and we have three subcategories, sidechains and relays, notary schemes and hash lot time contracts. I'm going to talk a bit more about this in a bit more detail. Then we have blockchain of blockchains, so essentially infrastructures like Polkadot and Cosmos, and then hybrid connectors that can connect not only public to private blockchains but also private to private blockchains and even non-public blockchains to centralized systems. So we have trusted relays or semi-trusted relays, blockchain agnostic protocols and blockchain migrators. And then we classify each solution that's on the references tab on the right according to a set of criteria. For example, in the asset type we can have data, so it's raw data, raw bytes. The plus sign indicates which one supports the transfer of raw data. And the red ones, the minuses represent the ones who cannot. We have data, payment tokens, P, and utility tokens. So essentially fungible, non-fungible tokens. Then we have the infrastructure, public blockchains, P, or non-public blockchains, so private blockchains, other types of hybrid decentralized ledgers, centralized systems, and P. Decentralization and essentially cross-chain realization. How are technically cross-chain transactions realized? How is the trust enforced in that cross-chain process? There are several ways of doing that. For example, I am mediated, or for example, escrowed cross-claim where you lock an asset in an origin block chain and you unlock it on the target block chain. The first public connector solution are sidechains and relays. A sidechain is an extension of the main chain that allows to offload competing power. So you can do different things that the main chain cannot do. An example of a sidechain of Bitcoin could be Ethereum or if we look it on the other way around, a sidechain of Ethereum can be Bitcoin because each block chain can post things on the other so we can offload functionality. Then we have relays that actually are relaying, transferring information from one chain to the other. If we combine those technologies, we can have something like the Bitcoin relay that is represented here. The Bitcoin relay is a smart contract on Ethereum that receives as input blockchain Bitcoin block headers. These Bitcoin block headers are sent as input by validators, by nodes, by Ethereum nodes, they receive a reward. Those nodes, those headers are computed and validated. This allows the Ethereum network, the smart contracts and nodes on the Ethereum network to be able to perform computation over those blocks which are essentially proofs that, they contain proofs that a certain transaction occurred in the Bitcoin blockchain. So it allows to conditionally execute transactions based on what happened at the Bitcoin network. The second subcategory are notary schemes. Notary schemes are centralized systems typically that perform the role of a mediator. So in case of exchanges and users can give dollars, they exchange buys or acquires Bitcoin, another cryptocurrency for example, and they give it back to the users on their walls. They're also decentralized exchanges but for the sake of time we're not covering them. Hashtag time contracts are so far a very good way to perform cross-chain functionality without the trust of the intermediary. These figure is from the cross-claim paper presentation, a very good paper and a very good presentation where hashtag time contracts are stead. So basically hashtag time contract is a scheme, a mechanism where two parties participating on two blockchains create a smart contract that has some conditional logic for transferring an asset to the other party on both blockchains. So essentially that is a secret that is generated in this case by Alice and she publishes a smart contract on her blockchain such that if you provide that secret, actually she publishes the hash on that secret, then she'll transfer you the asset. Bob sees this smart contract and publishes another smart contract with that secret with the same hash encoded in the smart contract which means that if Alice provides the secret, then Bob sends her the tokens that she wants on the blockchain and then he has the secret so he can redeem his assets on the other blockchain. Then blockchain of blockchains are frameworks that provide essentially a full stack for creating blockchain decentralized apps or blockchain specific apps more concretely and they come with let's say free interoperability because typically those infrastructures have as a mean of connecting its subchains a relay chain. So it's the interoperability processes are conducted via a blockchain or via a network that relays transactions and assures the overall global state consistency. In case of Polkadot it's based on parachains that are essentially shards of the main chain that allows to run application specific blockchains. There are some entities, some nodes that collect the transactions from there, from each parachain that produce blocks and that send the blocks to the relay chain and that relay chain transmits the blocks to all the parachains or to the involved parachains and this allows cross parachain communication cross parachain interoperability between the several chains and this is based on substrate that's developed in REST. This actually provides a good level of interoperability between the instances of that infrastructure not necessarily with other blockchains although there are apparatus called bridges that try to solve these problems and then we have hybrid connectors there is quite a lot of work in this category so I'm going to focus on trusted relays or semi-trusted relays in which you have included as examples hyperledger cactus, the most recent hyperledger project dedicated to interoperability and also ODEB, the open digital asset protocol. So hyperledger cactus is at the moment quite a fairly developed project there is still no version one release but it already supports a variety of ledgers fabric, hyperledger bezel, quorum, corda and there are some ongoing connectors being built like polka dots, aroha, sawtooth and so on. I won't be explaining cactus in detail because there's a presentation on it later by Peter and Shingo from hyperledger cactus but the idea is that you have a cactus node that's basically an API server with plugins that can connect to several ledgers and execute business logic. It has a plugin-based architecture it needs to be secured by default so one of the key principles is that double spans should not occur so it should preserve the underlying blockchains security it has low impact deployment, a plugin architecture so toffee, toffee, excuse me. This is an example of how a cactus network could be built and this is a long-term example where cactus is no longer a trusted relay but a semi-trusted relay where different organizations can establish a network of cactus nodes connected to different ledgers so you would not only... you would extend the trust boundaries of a single blockchain to a consortium of nodes that operate on those blockchains so you have cactus nodes as the most core unit and you could have a plugin called a consortium plugin and the goal of this plugin is to connect to other cactus nodes and to ensure that business logic is respected or at least that accountability is provided so if we agree to submit a transaction to Fabric when something happens on Ethereum we would be sure that if that condition is not respected we would know and this assumption is valid in the enterprise environment but other trust assumptions could be made now there are different plugins we could validate what's going on on Fabric we could connect to Ethereum-issued transactions and these nodes have really nicely nicely done SDKs that clients could connect to so we could build applications on top of these clients there are also some standards and supporting technologies around this topic in particular ISO, IEEE, the European Commission and IETF are working on standardizing blockchain interoperability it is a very difficult challenge because there's a lot of layers to be covered so the technical and synthetic layers are mostly technical work but on top of that the semantic layers require a lot of work from standardization bodies so in particular what is the protocol between two consortia that rules interoperability between blockchains what is an asset transfer what is data exchange and challenges like that the open-digital asset protocol tries to provide the answer to that and then we have other layers such as the application layer that rules out the domain of the applications built on top of those protocols and also for example the legal layer other supporting technologies include decentralized identifiers and verifiable credentials which promote identity portability that is very important in the blockchain interoperability area also we're starting to assist the emergence of cross-chain programming languages such as demos that will also provide a useful abstraction on managing from an application point of view several blockchains another concept that relates to this is the blockchain view ongoing work with my co-authors that helped on this paper a blockchain view is essentially a data abstraction that takes place that starts in building a snapshot of the original blockchain it builds something called a view that's a stakeholder specific view of those states that compose the blockchain then we can do interesting things with the views such as merging views checking differences between views and processing views these allow us to do interesting things such as auditing blockchain migration and analytics for example some topics I consider interesting for exploring and studying the interoperability between diverse different public private blockchains blockchain migration, decentralized identity, standardization blockchain of blockchain's approach these are very hot research areas nowadays so to conclude blockchain interoperability is an expansion people are starting to study it and to realize that it is needed for blockchain interoperability to mature in particular such as like the internet had its full potential when we started connecting local networks I believe something similar will happen with blockchain when we start connecting them will have network effects that so far we're not considering therefore it could promote flexibility, portability of solutions risk reduction bringing more players into blockchain finally it could promote mass adoption because data and value cells are eliminated and synergies are enhanced as a final tweet I'll leave you this enterprise blockchain technology course it's available as a hyperledger lab and it aims to teach the basics of the foundations of blockchain not only enterprise blockchain but also public blockchains as well as introducing Fabric 2.2 currently there's no module on blockchain interoperability but I hope hopefully that it's added to this course and this concludes my talk thank you very much for attending and I'll be happy to answer any questions if there are some questions I would like to ask you to write something on the Q&A or in the chat we still have 10 minutes you're all content there's a question from Friso sorry if I'm not pronouncing it correctly is Cardano also interoperable with hyperledger okay so Cardano is a public blockchain if I'm not mistaken has the other token right I know that those public blockchains are doing some efforts on interoperating with each other but I don't think that as their main scope interoperating with private blockchains is a priority so hyperledger has also a multitude of projects Fabric is one of the most popular it's private so I don't think they're doing that effort to solve this question we have several interoperability projects such as Cactus and Weaver to make Fabric in particular to interoperate with Cardano it would be adding a plug-in connector to Cactus that essentially takes Cardano's SDKs and then can compute things based on that I hope that answers your question there are some more questions one from Igor what is the best way to start exploring and investigating blockchain interoperability okay that's a very good question that I also had when I started my studies in 2019 at the time there was some work that's true but it was very fragmented it is still a bit fragmented actually because as I'm writing this survey things are evolving quite quickly and it's very difficult to catch up even if you're only doing that so what I would recommend you is to check those surveys that I have on the related work of my own survey and also my own survey because the goal of a survey is precisely to encompass all the work or most of the work that is being done in a particular area however, might be a limitation these surveys are more directed to academic work so they might leave out some grey literature like white papers out I've tried to cover that as well but there's so much material nowadays that it's difficult to keep up so if you know those basics those projects that are the core that are a bit older then I think that's a good basis for understanding the area in general thank you for the question Ralph asks when and when is your presentation available I think those will be available in YouTube in the hyperlogic channel when I don't know hopefully not too late then asks do you know institutions that certify blockchain solutions what do you mean I'm not sure what do you mean by that if you mean so if you could clarify the question it would be good if you mean certifying blockchain interoperability solutions no, I don't think so alright so could you please explain a bit more about the stakeholder specific views I don't get how that works but it sounds useful let me show you quickly so this is ongoing work it's very recent it's actually not published so the idea is that each stakeholder each participant on a blockchain has a different view they may have a different view of a blockchain okay in private blockchain this is in public blockchain so let's start there it happens with temporary forks right where we're different nodes and we temporarily see different chains right, eventually we choose the right one but those different forks might provide provide different information that we could reason about right on the other hand those views those different views are not temporary typically but they're permanent in the sense that we view different data if we have capabilities such as private data so this creates different views according to which private data collection are you participating at in case of fabric so the idea here is to collect the individual specific view of each stakeholder so we can for example compare them and see understand what one stakeholder can see at each moment of time and the other cannot this is very useful for other things for example if you want to migrate the blockchain solution this is also useful because we want all the stakeholders to be agreeing on the state to be migrated and if they cannot access the same state that's a problem so first we need to generate views for each one aggregate them into a consolidated view after that we can take the integrated view right and migrate the data of the system that is the general idea thank you for your question alright and I think we're running out of time but probably there's time for one or two more questions Thomas asks what's the channel name I suppose you're asking about the video it's hyper ledgers but for sure you will receive an email with that information Giacomo asks sorry I'm pretty sure I got the pronunciation wrong I think that's Italian which are the dangers in interoperability with malicious actors alright so one of the dangers and one of the major dangers I would say is that there at the moment there needs to be some sort of trust level between the networks that are interoperating right or between the gateways that are connecting those networks so in case of all that the open digital protocol that we're developing at the internet engineering task force the assumption is that the gateways are trusted the gateways are not lying because there are accountability mechanisms that keep track of the directions so if double spend actually occurs because I lied to you and I didn't lock my asset then they could be held accountable because their actions are tracked and then you could use the governance the legal frameworks to take action on that so interoperability requires trust assumptions because it's actually extending trust between partners so some scenarios require more trust other scenarios require less trust it's specific to the solution and this also partially answers the next question what's the most difficult saying into interoperability and I believe that one of them is to set boundaries set the right boundaries the right trust assumptions and enforce the right behavior in the protocols and those that are conducted such processes it's still all pretty recent all pretty new so it's difficult to get it right at the first time I would say all right and thank you very much everyone for attending it's really nice to be the speaker for your first session I hope you have a great hyperledger Global Forum cheers and take care