Meet YUI, one of the new Hyperledger Labs taking on cross-chain and off-chain operations

As enterprises and organizations increase their adoption and deployment of blockchain technology and networks, the overall complexity of systems are growing exponentially. While it’s exciting to see the expanding reach of blockchain, it also creates a host of new requirements for cross chain and off chain sharing of data, transactions and more. 

At Hyperledger Global Forum (HGF) 2020 in Phoenix, one group of developers got together to share their work and create a blockchain integration tool designed to allow users to securely integrate different blockchains. They brought their project to Hyperledger Labs and, within a few months, it was approved as Hyperledger Cactus

During this year’s HGF, three new Hyperledger Labs that are each tackling elements of cross-chain or off-chain operations are making their debuts: FireFly, Weaver and YUI. Read on to learn more about YUI.

Meet YUI 

By Jun Kimura (, CTO of Datachain (

YUI is a new Hyperledger Labs project to achieve interoperability between multiple heterogeneous ledgers. The word “YUI” is derived from a Japanese word to represent knot, join and connect.

YUI provides modules and middleware for cross-chain communication as well as modules and tools for cross-chain application development, including an explorer to track status and events for cross-chain environments.

This is the brief summary of YUI’s design principles.

Cross-Authentication: Cross-authentication allows blockchains to be interoperable without requiring a trusted third party by on-chain verification.

Blockchain-agnostic communication specs: By using a unified communication protocol, we can introduce a blockchain-agnostic message layer between blockchains.

Arbitrary data transfer and computation: By exchanging messages with a unified communication protocol, arbitrary data transfer and computation is possible. It also enables developers to implement arbitrary application logic that is not limited to a token transfer.

Avoid adding components that introduce additional trust: Introducing such components that need additional trust may decrease the level of security of a system as it would be bounded by the lowest security component in the system.

Do not introduce a new layer: Each actor (of ledgers) has only to interact with a respective ledger of its interest to complete a cross-chain operation unless the application has additional requirements.

Check out the YUI’s Lab page to learn more about the design principles of YUI:

High Level Architecture

For now, the modules and middleware for cross-chain communication (IBC Module) are available. The basic components of IBC Module are described in the following diagram:

As you can see on the diagram, we have an IBC Module on each ledger and a Relayer between them. As Client modules should be designed to support each underlying ledger, we have built different Client modules for each ledger such as Client modules for Hyperledger Fabric and for Hyperledger Besu.

For cross-chain communication, the design of YUI is based on Inter Blockchain Communication (IBC) protocol by Cosmos project, with extensions to support various Hyperledger projects.

Check out the IBC GitHub page to learn more about IBC and related words:

Get added background from this session at HGF: Fabric-IBC, Besu-IBC Combined with IRITA – Bringing Interoperability on Enterprise Blockchain – Zhiwei (Jeffrey) Hu, Shanghai Bianjie AI Co., Ltd. & Ryo Sato, Datachain, Inc.

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