Corda:如何向网络上的其他各方显示双方之间的协议？

Question

爱丽丝和鲍勃有一份欠条协议。如果爱丽丝想证明她真的和鲍勃有协议，她有没有可能把和鲍勃的借条协议拿给查利看？查利如何验证爱丽丝和鲍勃之间的借条是真的而不是假的？这个用例的流程是什么？

Answer 1

爱丽丝可以通过将创建协议的事务发送给查利，向查利证明她与鲍勃之间存在有效的协议。

然后，查理会检查事务是否有效，是否具有所有必需的签名者，以及是否已由Alice和Bob签名。

下面的流对将实现这一点：

/**
 * Sends a transaction with the given [txHash] to the [counterparty]:
 *
 * @param txHash the transaction to send.
 * @param counterparty the counterparty to send the transaction to.
 */
@InitiatingFlow
@StartableByRPC
class Initiator(val txHash: SecureHash,
                val counterparty: Party) : FlowLogic<Unit>() {

    @Suspendable
    override fun call() {
        val tx = serviceHub.validatedTransactions.getTransaction(txHash)!!
        val counterpartySession = initiateFlow(counterparty)
        counterpartySession.send(tx)
    }
}

/**
 * Receives a transaction from the counterparty and checks that:
 *  - It is valid
 *  - It has valid signatures from all required signers
 *  - The [requiredSigners] have all signed the transaction
 *
 * @param counterpartySession a session with the party sending the transaction to be checked.
 * @param requiredSigners the parties who are required to have signed the transaction.
 */
@InitiatedBy(Initiator::class)
class Acceptor(val counterpartySession: FlowSession,
               val requiredSigners: List<CordaX500Name>) : FlowLogic<SignedTransaction>() {

    @Suspendable
    override fun call(): SignedTransaction {
        return counterpartySession.receive<SignedTransaction>().unwrap { tx ->
            // Transaction is valid and all the required signatures are present and valid.
            tx.verify(serviceHub)

            val requiredSigningParties = requiredSigners.map { serviceHub.networkMapCache.getPeerByLegalName(it)!! }
            val allHaveSigned = requiredSigningParties.all { party -> tx.sigs.any { sig -> sig.by == party.owningKey } }

            if (!allHaveSigned) {
                throw FlowException("The required parties have not signed the transaction.")
            }

            // TODO: Additional checking of the transaction (e.g. the properties of the inputs and outputs).

            tx
        }
    }
}