• Overview
• Usage
  • Installation
  • Data Sharing
    • COPM Command
    • Figure: Data Sharing with getVerifiedState
  • Asset Transfer
    • COPM Commands
    • Figure: Asset Transfer Pledge and ClaimPledge
  • Asset Exchange
    • COPM Commands
    • Figure: Asset Exchange with Lock and ClaimLock
• Development

Overview

This package defines the common types, interfaces, and endpoints for the COPM module to be used by Digital Ledger-specific implementations.

These endpoints require specific chaincode and weaver relays to be deployed on the network. Please refer to the Weaver documentation.

Usage

For a detailed command specification, please refer to the OpenAPI Endpoint Documentation

Installation

Yarn:

yarn add --exact @hyperledger-cacti/cacti-copm-core

Data Sharing

• ability to read data on another network
• the other network must first give you permission

COPM Command

• getVerifiedState

Figure: Data Sharing with getVerifiedState

sequenceDiagram
    participant Alice
    participant COPM gRPC A
    participant Ledger A
    participant Relay A 
    participant Relay B
    participant Ledger B as Ledger B 
    Alice->>COPM gRPC A: getVerifiedState for State X on Ledger B
    activate COPM gRPC A
    COPM gRPC A->>Relay A: Read State X on Ledger B
    activate Relay A
    Relay A->>Relay B: Read State X
    activate Relay B
    Relay B->>Ledger B: Read State X
    activate Ledger B
    Ledger B->>Ledger B: Check permissions 
    Ledger B->>Ledger B: Read State X
    Ledger B->>Relay B: Return signed State X
    deactivate Ledger B
    Relay B->>Relay A: Return signed State X
    deactivate Relay B
    Relay A->>COPM gRPC A: Return signed State X
    deactivate Relay A
    COPM gRPC A->>Ledger A: Verify signature
    activate Ledger A
    Ledger A->>Ledger A: Verify signature
    Ledger A->>COPM gRPC A: Signature Verified
    deactivate Ledger A
    COPM gRPC A->>Alice: Return State X
    deactivate COPM gRPC A

Asset Transfer

• Asset changes networks
• Asset burnt on Ledger A, minted on Ledger B
• Introduces 2 ledger data types:
  • Pledge
    • A record created on Ledger A when an asset is burnt
    • Contains details about the asset, who it is promised to
  • Claim
    • A record created on Ledger B when the pledged asset is minted

COPM Commands

• Pledge
• ClaimPledge

Figure: Asset Transfer Pledge and ClaimPledge

sequenceDiagram
    actor Alice
    actor Bob
    participant System A 
    participant Asset
    participant System B
    note right of System B:System: Ledger, <br/>Relay, COPM gRPC
    Alice->>Bob: Would you like my Asset?
    Bob->>Alice: Yes, please.
    Alice->>System A: Pledge Asset
    activate System A
    System A->>System A: Create Pledge
    destroy Asset
    System A-xAsset: Burn
    deactivate System A
    Alice->>Bob: You can claim it now!
    Bob->>System B: Claim Pledge
    activate System B
    rect rgb(191, 223, 255)
      System B->>System A: Read Pledge on System A
      activate System A
      note right of System B: A cross-network <br/>'Data Sharing' flow
      System A->>System A: Read Pledge
      System A->>System B: Return signed pledge
      deactivate System A
    end
    System B->>System B: Create Claim
    create participant PB as Asset
    System B->>PB: Mint
    deactivate System B

Asset Exchange

• Assets stay where they are
• Two parties swap asset ownership of two assets
  • Assets can be on different networks
• Uses HTLC (Hash Time Lock Contract)
• Both parties have visibility of both assets/networks
• No inter-network communication needed
  • no relays

COPM Commands

• Lock
• ClaimLock

Figure: Asset Exchange with Lock and ClaimLock

sequenceDiagram
    actor Alice
    actor Bob
    participant Token System
    participant Bond System
    note right of Bond System: System: Ledger and COPM gRPC
    Alice->>Bob: Would you like to trade my Tokens for your Bond?
    Bob->>Alice: Yes, please.
    Alice->>Token System: Lock Tokens
    activate Token System
    Token System->>Token System: Lock Tokens
    deactivate Token System
    Bob->>Bond System: Lock Bond
    activate Bond System
    Bond System->>Bond System: Lock Bond
    deactivate Bond System
    Alice->>Bob: I've locked my Tokens, the secret is X.
    Bob-->>Token System: Sees Tokens are Locked
    Bob->>Alice: I've locked my Bond, the secret is Y.
    Alice-->>Bond System: Sees Bond is Locked
    Alice->>Bond System: Claim Lock for Bond with secret Y
    activate Bond System
    Bond System->>Bond System: Verify Lock
    Bond System->>Bond System: Change Bond owner to Alice
    deactivate Bond System
    Bob->>Token System: Claim Lock for Tokens with secret X
    activate Token System
    Token System->>Token System: Verify Lock
    Token System->>Token System: Change Token owner to Bob
    deactivate Token System

Development

When implementing a new distributed ledger, the following interfaces must be implemented:

• DLTransactionContext: Implements running a transaction on the local network
• DLRemoteTransactionContext: Uses the weaver relays to run a transaction on another network
• DLTransactionContextFactory: Factory to return either local or remote context for the specific DLT.