Demo: Interoperability with Hyperledger Lab YUI

Koji Matsumiya, a software engineer at Datachain, gave a presentation at Hyperledger Global Forum 2022.

Learn more about YUI from the link below.
https://github.com/hyperledger-labs/yui-docs

About the session
https://hgf22.sched.com/event/176nS?iframe=no
This session covers the basic idea of YUI and how to use YUI to achieve cross-chain transactions (interoperability) between different blockchains. YUI is a lab to achieve trustless interoperability between multiple heterogenous ledgers using Cosmos' IBC protocol. As YUI supports permissioned blockchains such as Hyperledger Fabric, Hyperledger Besu, Hyperledger Iroha and Corda, enterprise companies such as NTT DATA, JCB and HITACHI have conducted proof-of-concept using YUI. The session will explain how to implement YUI modules to enable interoperability in those use cases above.

Transcript

1. Copyright © 2022 Datachain, Inc. All Rights Reserved.
   Demo: Interoperability with
   Hyperledger Lab YUI

   Datachain, Inc
   Software Engineer
   Koji Matsumiya
   

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2. Copyright © 2022 Datachain, Inc. All Rights Reserved. 2
   Agenda
   ● What is YUI
   ● IBC Overview
   ● How YUI Works
   ● Comparison of Interoperability Methods
   ● Demo: Token Transfer between Hyperledger Fabric and Cosmos
   ● Current Work: LCP
   

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3. Copyright © 2022 Datachain, Inc. All Rights Reserved. 3
   What is YUI
   ● YUI is a Hyperledger Lab project to facilitate interoperability between multiple
   heterogeneous blockchains
   ● YUI provides modules and middleware for cross-chain communication
   ● YUI follows on Inter Blockchain Communication (IBC) protocol by Cosmos
   ● Core concepts
   ○ Do not require additional trust by on-chain verification
   ○ Support arbitrary data transfer and computation
   ○ Enable developers to develop chain-independent
   yui-fabric-ibc yui-ibc-solidity
   yui-corda-ibc
   YUI
   A Project to Achieve Interoperability Between Multiple Heterogeneous Ledgers
   Application Module
   IBC Module
   Development Tools
   Explorer
   etc.
   Modules to support the development of cross-chain contracts
   Client (on-chain) modules to support various ledgers in align with the design
   principles
   To be included in YUI
   Relayer
   Available in
   YUI
   a middleware to relay
   packets between sets
   of various ledgers.
   See also
   hyperledger-labs/yui-docs at the
   below link for more details
   https://github.com/hyperledger-labs/yui-docs
   To be included in YUI
   

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4. Copyright © 2022 Datachain, Inc. All Rights Reserved.
   Host Machine IBC Module
   4
   IBC Overview
   ● IBC is an implementation as the inter-blockchain communication protocol (ICS) by
   Interchain Foundation
   ● IBC is a layered protocol for interoperability between different ledgers
   ● IBC is the core piece of Cosmos
   ○ Cosmos provides Cosmos SDK to develop a blockchain
   ○ Enable Cosmos SDK-based blockchains interoperability
   ○ Cosmos Hub is a well-known network
   App Module
   Routing Module
   Handler Module
   Client Module
   Connection
   Module
   Channel Module
   Port Module
   App Module
   App Module
   B depends on A
   A B
   Module layout
   

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5. Copyright © 2022 Datachain, Inc. All Rights Reserved.
   IBC Modules
   5
   How YUI Works
   ● YUI enables interoperability with the IBC-based Light Client method
   ● Light clients are a core component to trace and verify counterparty states at local
   ○ Light clients require a block header for verification
   ○ One side needs to implement a light client of the other side
   ● Relayer has a role in the physical connection of IBC
   ○ Relayer detects and transmits packets from one to the other
   ○ Relayer is an off-chain process but is permissionless and trustless
   App Module
   Hyperledger Fabric
   App Module
   Cosmos
   yui-relayer
   off-chain process
   IBC Modules
   Fabric Client
   in yui-fabric-ibc
   6. Send a packet
   5. Verify a header & update
   8. Call a function
   2. Detect a packet
   1. Create a packet
   Flow: Cosmos send a packet to Hyperledger Fabric
   3. Get a latest header
   4. Submit a header
   7. Verify a packet
   Tendermint Client
   in ibc-go
   

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6. Copyright © 2022 Datachain, Inc. All Rights Reserved. 6
   Comparison of Interoperability Methods
   ● Pros for Light Client method
   ○ More secure
   External Validators method
   Trusted Third Party
   Verified by third party outside of both sides
   HTLC method
   Protocol using a hash lock and a time lock
   between parties
   Light Client method
   Verified one chain by the other
   This method is simple but does not
   support complex logic.
   This method requires no additional trust,
   but costs more for the chain.
   Blockchain X
   Token
   s
   方
   式
   を
   採
   用
   Blockchain Y
   Token
   Blockchain X
   Token
   Blockchain Y
   Token
   監視
   監視
   Blockchain X
   Blockchain Y
   Token
   Verify
   Hash
   Token
   Hash
   This method requires additional trust,
   but costs less for the chain.
   ● Cons for Light Client method
   ○ Low extensibility
   ○ High verification cost
   

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7. Copyright © 2022 Datachain, Inc. All Rights Reserved. 7
   Demo: Token transfer between Hyperledger Fabric and Cosmos
   ● Transfer fungible token between Hyperledger Fabric and Cosmos by ICS-20
   ○ ICS-20 is a specification in IBC/APP
   ○ Refer to fabric-cosmos-ibc-demo repository
   ● Main components
   ○ yui-relayer: Relayer implementation for IBC
   ○ yui-fabric-ibc: IBC implementation in Golang for Hyperledger Fabric.
   ○ ibc-go: IBC implementation in Golang for Cosmos/Tendermint
   ■ Tendermint is a PoS consensus algorithm
   Relayer
   Cosmos Fabric
   1. Call token transfer from
   Cosmos to Fabric
   2. Lock token &
   Create a packet
   3. Detect a packet &
   Send to Fabric
   4. Verify a packet &
   Mint token &
   Create an ack packet
   5. Detect an ack packet &
   Send to Cosmos
   6. Verify an ack packet &
   Succeeded
   * Note that this sequence is simplified.
   

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8. Copyright © 2022 Datachain, Inc. All Rights Reserved. 8
   Demo: Directory Structure
   The chaincode and contract include an IBC
   application that references the transfer module for
   Fabric and Cosmos
   The networks includes environments such as
   Dockerfile, utility scripts, and some configs for
   launch blockchain respectively
   The relayer refers to yui-relayer repository using
   Git-submodule
   The tests has demo scripts and relayer configs
   

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9. Copyright © 2022 Datachain, Inc. All Rights Reserved. 9
   Demo: How to implement business logic on Fabric and Cosmos
   ● Fabric
   ○ Running Chaincode like Smart Contract using Golang
   ○ The yui-fabric-ibc provides IBC Chaincode integrated Cosmos modules
   ○ Therefore, implement Cosmos modules as well as Cosmos blockchain
   ● Cosmos
   ○ Implement IBCModule based on Cosmos SDK in Golang
   type IBCModule interface {
   OnRecvPacket(
   ctx sdk.Context,
   packet channeltypes.Packet,
   relayer sdk.AccAddress,
   ) exported.Acknowledgement
   OnAcknowledgementPacket(
   ctx sdk.Context,
   packet channeltypes.Packet,
   acknowledgement []byte,
   relayer sdk.AccAddress,
   ) (*sdk.Result, error)
   OnTimeoutPacket(
   ctx sdk.Context,
   packet channeltypes.Packet,
   relayer sdk.AccAddress,
   ) (*sdk.Result, error)
   }
   05-port/…/module.go (showed only one part)
   type MsgServer interface {
   Transfer(context.Context, *MsgTransfer)
   (*MsgTransferResponse, error)
   transfer/…/msg_server.go
   Call when receiving a
   packet from Relayer
   Call when receiving an
   ack from Relayer
   Call when exceeding
   timeout
   There is an entry point to
   initiate token transfer
   

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10. Copyright © 2022 Datachain, Inc. All Rights Reserved. 10
    Demo: Relayer configurations
    {
    "src": {
    "chain-id": "ibc0",
    "client-id": "ibconeclient",
    "connection-id": "ibconeconnection",
    "channel-id": "ibconexfer",
    "port-id": "transfer",
    "order": "unordered",
    "version": "ics20-1"
    },
    "dst": {
    "chain-id": "ibc1",
    "client-id": "ibczeroclient",
    "connection-id": "ibczeroconnection",
    "channel-id": "ibczeroxfer",
    "port-id": "transfer",
    "order": "unordered",
    "version": "ics20-1"
    },
    "strategy": {
    "type": "naive"
    }
    }
    path.json
    {
    "@type": "/relayer.fabric.config.ChainConfig",
    "chain_id": "ibc1",
    "msp_id": "PlatformerMSP",
    "channel": "channel1",
    "chaincode_id": "trade",
    "connection_profile_path": "./ccp/platformer.yaml",
    "ibc_policies": ["PlatformerMSP"],
    "endorsement_policies": ["PlatformerMSP"],
    "msp_config_paths": ["./fixtures/msps/PlatformerMSP"]
    }
    ibc-1.json
    {
    "@type": "/relayer.tendermint.config.ChainConfig",
    "key": "testkey",
    "chain_id": "ibc0",
    "rpc_addr": "http://localhost:26657",
    "account_prefix": "cosmos",
    "gas_adjustment": 1.5,
    "gas_prices": "0.025stake",
    "trusting_period": "336h"
    }
    ibc-0.json
    Directory structure
    ● The path.json specifies a connection end to each other via IBC
    ● The ibc-x.json has a configuration to connect to one side
    ibc0 is Cosmos side
    ibc1 is Fabric side
    It is necessary to establish a
    connection via connection
    and channel handshake
    The port-id and version are
    needed to tie an application
    module
    const (
    ModuleName = "transfer"
    Version = "ics20-1"
    PortID = "transfer"
    )
    transfer/…/keys.go (showed only one part)
    

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11. Copyright © 2022 Datachain, Inc. All Rights Reserved.
    11
    Demo: Build
    ● Build IBC applications by make build
    .PHONY: build
    build:
    make -C chaincode build \
    && make -C contract build \
    && make -C relayer build
    Makefile
    .PHONY: build
    build:
    go build -mod=readonly -o $(CURDIR)/build/app $(CURDIR)/bin
    chaincode/Makefile
    .PHONY: build
    build:
    go build -mod=readonly -o ./build/simd ./simapp/simd
    contract/Makefile
    .PHONY: build
    build:
    go build -o ./build/uly .
    relayer/Makefile
    Build a Relayer CLI to interact with
    Fabric and Cosmos
    Build an IBC application
    with a transfer module for
    Fabric
    Build an IBC application
    with a transfer module for
    Cosmos
    As a result:
    

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12. Copyright © 2022 Datachain, Inc. All Rights Reserved. 12
    Demo: Setup
    ● Launch networks and initialize by make setup
    .PHONY: setup
    setup: start-cosmos start-fabric prepare
    .PHONY: start-fabric
    start-fabric:
    make -C networks/fabric start
    .PHONY: start-cosmos
    start-cosmos:
    make -C networks/cosmos up
    .PHONY: prepare
    prepare:
    make \
    RLY_BINARY=${CURDIR}/relayer/build/uly \
    TM_BINARY=${CURDIR}/contract/build/simd \
    MSPS_DIR=${CURDIR}/networks/fabric/msps \
    TM_DATA_DIR=${CURDIR}/networks/cosmos/fixtures/data \
    -C tests prepare
    Makefile
    The start-fabric launches the Fabric network as a
    Docker container
    The start-cosmos launches Cosmos network as a
    Docker container
    The prepare runs setup scripts and works below:
    - Initialize both networks
    - Create a light client respectively
    - Initiate opening handshake as defined by IBC
    Thus, It enables both chains to communicate via IBC
    

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13. Copyright © 2022 Datachain, Inc. All Rights Reserved. 13
    Demo: Setup
    ● As a result:
    Established channels
    Established connections
    Started Docker
    containers
    

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14. Copyright © 2022 Datachain, Inc. All Rights Reserved. 14
    Demo: Transfer via IBC
    ● Run a demo script by make transfer
    echo "!!! Tendermint -> Fabric !!!"
    echo "Before TM balance: $(${RLY} query balance ibc0 ${TM_ADDRESS})"
    echo "Before Fab balance: $(${RLY} query balance ibc1 ${FABRIC_ADDRESS} | tail -n
    1)"
    ${RLY} tx transfer ibc01 ibc0 ibc1 100samoleans ${FABRIC_ADDRESS}
    sleep ${TX_INTERNAL}
    ${RLY} tx relay ibc01
    sleep ${TX_INTERNAL}
    ${RLY} tx acks ibc01
    sleep ${TX_INTERNAL}
    echo "After TM balance: $(${RLY} query balance ibc0 ${TM_ADDRESS})"
    echo "After Fab balance: $(${RLY} query balance ibc1 ${FABRIC_ADDRESS} | tail -n 1)"
    test-tx (showed only a part of token transfer)
    transfer:
    make \
    RLY_BINARY=${CURDIR}/relayer/build/uly \
    TM_BINARY=${CURDIR}/contract/build/simd \
    MSPS_DIR=${CURDIR}/networks/fabric/msps \
    TM_DATA_DIR=${CURDIR}/networks/cosmos/fixtures/data \
    -C tests test
    Makefile Printed states before the token transfer
    Executed transfer on Cosmos
    Executed transfer on Fabric
    Printed states after the token transfer
    ● As a result:
    

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15. Copyright © 2022 Datachain, Inc. All Rights Reserved. 15
    Current Work: LCP (Light Client Proxy)
    ● LCP is another way to address Cross-chain communication
    ● LCP solves the following issues of the Light Client method
    ○ Low extensibility
    ○ High verification cost
    LCP Node and Enclave Light Client (ELC)
    - Equipped with Intel SGX
    - ELC verifies commitment proofs from each network
    submitted by Relayer
    - Verified result (commitment) is then signed with
    Enclave Key and sent to the other network by Relayer
    Attestation Service
    - Provide verifiable quote for soundness and public key
    of LCP Enclave
    Relayer
    - Exchange information with Chains and
    LCP Node
    LCP Client
    - IBC client that verifies the commitment by ELC
    - Public key of Enclave is attained through verification of
    Quote by Attestation Service
    datachainlab/lcp
    

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