多方工作流

Canton 如何处理与以太坊不同的多方工作流

多方工作流是 Canton 相对以太坊的突出优势。本节介绍关键模式与思维差异。

核心差异

以太坊上多方协议是你实现的模式；Canton 上是协议保证。

提议-接受模式

Canton 要求所有 signatory 授权创建，无法单方面创建多方合约。标准模式是 propose-accept：

sequenceDiagram
    participant Alice
    participant Bob
    participant Ledger

    Alice->>Ledger: Create Proposal (signatory: Alice, observer: Bob)
    Note over Ledger: Proposal exists<br/>Bob can see it
    Bob->>Ledger: Exercise Accept on Proposal
    Note over Ledger: Proposal archived<br/>Agreement created (signatory: Alice, Bob)

Daml 示例

template TradeProposal
  with
    proposer : Party
    counterparty : Party
    asset : Text
    price : Decimal
  where
    signatory proposer
    observer counterparty

    choice Accept : ContractId Trade
      controller counterparty
      do
        create Trade with
          buyer = counterparty
          seller = proposer
          asset
          price

    choice Withdraw : ()
      controller proposer
      do pure ()

template Trade
  with
    buyer : Party
    seller : Party
    asset : Text
    price : Decimal
  where
    signatory buyer, seller

与以太坊对比

Solidity 需手动 buyerApproved/sellerApproved 与 require；Canton 由协议强制授权、原子状态转移，可见性自动限定在参与方。

委托模式

Controller 委托

template Asset
  with
    owner : Party
    delegate : Optional Party
  where
    signatory owner

    choice Transfer : ContractId Asset
      with newOwner : Party
      controller case delegate of
        Some d -> d
        None -> owner
      do
        create this with owner = newOwner

独立委托合约

template DelegationAuthority
  with
    principal : Party
    agent : Party
    scope : [Text]
  where
    signatory principal
    observer agent

    nonconsuming choice ActOnBehalf : ()
      with action : Text
      controller agent
      do
        assertMsg "Action not in scope" (action `elem` scope)
        pure ()

多步工作流

flowchart LR
    subgraph Step1[Step 1: Proposal]
        A[Alice proposes]
    end
    subgraph Step2[Step 2: Approval]
        B[Bob approves]
    end
    subgraph Step3[Step 3: Execution]
        C[Charlie settles]
    end
    Step1 --> Step2 --> Step3

用 WorkflowState（Proposed / Approved / Settled）与按阶段不同 controller 的 Choice 实现状态机。

原子多合约操作

choice ExecuteSwap : ()
  with
    assetA : ContractId Asset
    assetB : ContractId Asset
  controller buyer, seller
  do
    exercise assetA Transfer with newOwner = buyer
    exercise assetB Transfer with newOwner = seller

以太坊原子交换需托管、时间锁、失败恢复与重入防护；Canton 由协议保证原子性——任一部分失败则全部不发生。

多方工作流中的隐私

单笔交易中 Alice 见全部、Bob 见 Trade 与收款、银行只见通知——各方只见相关 leg。

常见工作流模式

相关主题

本文由 CC Privacy Club 根据 Canton Network 官方文档（CC-BY-4.0）整理翻译，仅供学习；实现细节以官方最新版本为准。