Shun Takagiwa / 高際 隼 Senior Software Architect, LayerX Inc. Core maintainer of Cordage • Joined LayerX Inc. since it was founded in August 2018 • Responsible for multiple projects as a technical lead ◦ e.g. MUFG, MITSUI & CO., LTD., Cryptorealty, etc • In charge of product concept design, agile software development, system design, implementation, and operation • The CEO Special Award 2019, The Core Values Award 2020 @shun_tak
Since Bitcoin, many blockchain products and use cases came out Increasing demands to connect other products • e.g. Quorum vs Corda in Ubin-Jasper project • e.g. Hyperledger Fabric vs Corda in Deutsche bank project Blockchain interoperability provides tighter and more secure coupling between platforms than is possible with existing systems
of blockchain interoperability • Connect blockchain and existing system ◦ e.g. Import Swift data into blockchain • Connect different dapps on the same blockchain ◦ e.g. Decentralized exchange (DEX) ◦ e.g. Decentralized finance (DeFi) • Connect the same type of different blockchains ◦ e.g. Quorum vs other Quorum • Connect different types of blockchains ◦ e.g. Quorum vs Corda From now, let’s discuss the latter 2 types of interoperability Typically discussed blockchain interoperability
Applications for blockchain interoperability • Cross-Chain Atomic Swap ◦ e.g. Cross-Chain DvP Settlement • Cross-Chain Oracle ◦ e.g. Take prices from Uniswap on Ethereum mainnet and use them on other blockchain • Pegged Asset ◦ e.g. Wrapped BTC • Asset Portability ◦ e.g. Move an asset between blockchain shards • Automatic Payment ◦ e.g. Transfer ether or bitcoin in accordance with OpenLaw's contract enforcement terms
schemes of blockchain interoperability Trusted intermediaries Relays HTLC Overview Trust model Majority of intermediaries honest Depends on each blockchains Depends on each blockchains Ease of implementation Medium Hard Easy Required functions • Fetching events • Propagating events • Intermediaries consensus • On-chain verification for intermediaries signatures • Fetching events • Propagating events • Verifying events correctness • Verifying events finality • Fetching data • Propagating data • Ability to time locking • Cryptographic hash function Applicability to use cases Any use cases (Some use cases require long-term intermediaries trust) Any use cases (Some use cases require bidirectional relays) Specialized to atomic swap (Asset portability and automatic payments are difficult) Ref: Chain Interoperability by Vitalik Buterin A B A B A B TI scheme depends on intermediaries honest while relays are too hard to implement In the consortium area, we can take advantage of blockchain operators to improve TI scheme security
makes the interoperability possible between Corda and Ethereum based blockchain without additional trusted intermediaries What is Cordage Features • Connect Ethereum based blockchain with Corda • No need to run an additional process So, how is Cordage’s interoperability scheme like?
interoperability scheme Trusted intermediaries Cordage scheme Overview Trust model Majority of intermediaries honest Depends on each blockchains Ease of implementation Medium Medium Required functions • Fetching events • Propagating events • Intermediaries consensus • On-chain verification for intermediaries signatures • Fetching events • Propagating events • Light client of blockchain B that works on blockchain A’s smart contract Applicability to use cases Any use cases (Some use cases require long-term intermediaries trust) Any use cases A B A B Same security level as relays Higher than TI scheme Easier than Relays Higher availability than TI scheme due to no intermediaries Corda is able to run the Ethereum light client
Cordage’s interoperability scheme works Propagating events 1. Make an ethereum transaction that includes data on Corda 2. Sign the transaction with the Ethereum private key owned by Corda Notary 3. Send the transaction to Ethereum node Corda Notary signs to guarantee correctness and finality on Corda Fetching events 1. Watch logs in transaction receipts on Ethereum 2. Parse logs by using ABI and encoder 3. Store them to Corda Both actions are run from Corda Nodes or Corda Notary, not the additional intermediaries Access authority to the Ethereum RPC endpoint is required 3. Send the tx 1. Watch logs 2-3. Parse and store logs 1-2. Make and sign the tx
Atomic Swap with Cordage Disclaimer This is a minimal viable product to confirm swapping assets in atomic among blockchains. You may need additional features in production such as the privacy feature.
Atomic Swap with Cordage Scenario • Ether and corporate bond are minted in advance • Alice wants to buy 100 amount of corporate bond that is owned by Bob ◦ Alice remits by ether to Bob (The unit price is specified with the initial corporate bond registration) ◦ Bob transfers 100 amount of corporate bond to Alice ◦ These are expected to happen in atomic Steps to cross-chain atomic swap 1. By running ProposeAtomicSwapFlow, Alice creates a ProposalState and asks Bob to sign 2. LockEtherFlow is started automatically by ProposeAtomicSwapFlow after its finality 3. By running StartEventWatchFlow once, Bob watches Ethereum logs with running EventWatchFlow every 5 seconds 4. SettleAtomicSwapFlow is started automatically by EventWatchFlow if it finds a targeted log (LockEtherEvent) 5. In the SettleAtomicSwapFlow, Bob transfers corporate bond to Alice, and at the same time Corda Notary unlocks and sends the ether to Bob https://github.com/LayerXcom/cordage/tree/ master/cross-chain-atomic-swap-cordapp
• Version 0.3 ◦ Implement exception scenario for cross-chain atomic swap (Currently under testing) • Improvements ◦ Enhance documentation ◦ Implement additional sample applications • Version 1.0 ◦ Transform modules to work as maven (gradle) libraries • New features ◦ Support Hyperledger Fabric
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