1 of 18

Introduction to

https://youtu.be/f1ZPXvoVyj8?t=3477

2 of 18

Speaker

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

2

3 of 18

Agenda

Overview of blockchain interoperability
What is Cordage
Cross-Chain Atomic Swap with Cordage
Demo
Milestones

3

4 of 18

Overview of�blockchain interoperability

4

5 of 18

Background

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

5

6 of 18

Types 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

6

7 of 18

Example 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

7

8 of 18

3 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

8

Trusted intermediaries

a party or a group of parties agree to carry out an action on blockchain B when some event on blockchain A takes place.

Data correctness is guaranteed by the majority of intermediaries' signatures.

So you have to implement consensus among intermediaries and need to take care of intermediaries' availability.

Relays

relayers read events in blockchain A and propagate them to blockchain B. smart contracts inside of blockchain B validate propagated data.

Data correctness and finality are verified on blockchain B so that anyone can be relayers.

The difference between ‘Trusted intermediaries scheme’ and ‘Relays scheme’ is that the propagated data’s correctness is assured by intermediaries.

On the other hand, relayers don’t need to assure correctness because blockchain B validates data by itself.

However, the relays scheme is very hard to implement. To validate propagated data, you need to implement blockchain A’s consensus by using blockchain B’s smart contract.

HTLC

setting up operations on blockchain A and blockchain B that have the same trigger, usually the revelation of the preimage of a particular hash

9 of 18

What is Cordage

9

10 of 18

Cordage 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?

10

11 of 18

Cordage’s 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

11

12 of 18

How Cordage’s interoperability scheme works

Propagating events

Make an ethereum transaction that includes data on Corda
Sign the transaction with the Ethereum private key owned by Corda Notary
Send the transaction to Ethereum node

Corda Notary signs to guarantee correctness and finality on Corda

Fetching events

Watch logs in transaction receipts on Ethereum
Parse logs by using ABI and encoder
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

12

13 of 18

Cross-Chain 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.

13

14 of 18

Cross-Chain 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

By running ProposeAtomicSwapFlow, Alice creates a ProposalState and asks Bob to sign
LockEtherFlow is started automatically by ProposeAtomicSwapFlow after its finality
By running StartEventWatchFlow once, Bob watches Ethereum logs with running EventWatchFlow every 10 seconds
SettleAtomicSwapFlow is started automatically by EventWatchFlow if it finds a targeted log (LockEtherEvent)
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

14

15 of 18

Demo

15

16 of 18

Milestones

16

17 of 18

Milestones

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

17

18 of 18

GitHub https://github.com/LayerXcom/cordage

Gitter chat https://gitter.im/LayerXcom/Cordage

18