Golang Transaction.SigHash方法代碼示例

// negotiateRevision sends a revision and actions to the host for approval,
// completing one iteration of the revision loop.
func negotiateRevision(conn net.Conn, rev types.FileContractRevision, secretKey crypto.SecretKey) (types.Transaction, error) {
	// create transaction containing the revision
	signedTxn := types.Transaction{
		FileContractRevisions: []types.FileContractRevision{rev},
		TransactionSignatures: []types.TransactionSignature{{
			ParentID:       crypto.Hash(rev.ParentID),
			CoveredFields:  types.CoveredFields{FileContractRevisions: []uint64{0}},
			PublicKeyIndex: 0, // renter key is always first -- see formContract
		}},
	}
	// sign the transaction
	encodedSig, _ := crypto.SignHash(signedTxn.SigHash(0), secretKey) // no error possible
	signedTxn.TransactionSignatures[0].Signature = encodedSig[:]

	// send the revision
	if err := encoding.WriteObject(conn, rev); err != nil {
		return types.Transaction{}, errors.New("couldn't send revision: " + err.Error())
	}
	// read acceptance
	if err := modules.ReadNegotiationAcceptance(conn); err != nil {
		return types.Transaction{}, errors.New("host did not accept revision: " + err.Error())
	}

	// send the new transaction signature
	if err := encoding.WriteObject(conn, signedTxn.TransactionSignatures[0]); err != nil {
		return types.Transaction{}, errors.New("couldn't send transaction signature: " + err.Error())
	}
	// read the host's acceptance and transaction signature
	// NOTE: if the host sends ErrStopResponse, we should continue processing
	// the revision, but return the error anyway.
	responseErr := modules.ReadNegotiationAcceptance(conn)
	if responseErr != nil && responseErr != modules.ErrStopResponse {
		return types.Transaction{}, errors.New("host did not accept transaction signature: " + responseErr.Error())
	}
	var hostSig types.TransactionSignature
	if err := encoding.ReadObject(conn, &hostSig, 16e3); err != nil {
		return types.Transaction{}, errors.New("couldn't read host's signature: " + err.Error())
	}

	// add the signature to the transaction and verify it
	// NOTE: we can fake the blockheight here because it doesn't affect
	// verification; it just needs to be above the fork height and below the
	// contract expiration (which was checked earlier).
	verificationHeight := rev.NewWindowStart - 1
	signedTxn.TransactionSignatures = append(signedTxn.TransactionSignatures, hostSig)
	if err := signedTxn.StandaloneValid(verificationHeight); err != nil {
		return types.Transaction{}, err
	}

	// if the host sent ErrStopResponse, return it
	return signedTxn, responseErr
}

// verifyKeysSiag_1_0 is a copy-pasted version of the verifyKeys method
// from siag 1.0.
func verifyKeysSiag_1_0(uc types.UnlockConditions, folder string, keyname string) error {
	keysRequired := uc.SignaturesRequired
	totalKeys := uint64(len(uc.PublicKeys))
	loadedKeys := make([]KeyPairSiag_1_0, totalKeys)
	for i := 0; i < len(loadedKeys); i++ {
		err := encoding.ReadFile(filepath.Join(folder, keyname+"_Key"+strconv.Itoa(i)+".siakey"), &loadedKeys[i])
		if err != nil {
			return err
		}
	}
	for _, loadedKey := range loadedKeys {
		if loadedKey.UnlockConditions.UnlockHash() != uc.UnlockHash() {
			return errors.New("ErrCorruptedKey")
		}
	}
	txn := types.Transaction{
		SiafundInputs: []types.SiafundInput{
			types.SiafundInput{
				UnlockConditions: loadedKeys[0].UnlockConditions,
			},
		},
	}
	var i uint64
	for i != totalKeys {
		if i+keysRequired > totalKeys {
			i = totalKeys - keysRequired
		}
		var j uint64
		for j < keysRequired {
			txn.TransactionSignatures = append(txn.TransactionSignatures, types.TransactionSignature{
				PublicKeyIndex: i,
				CoveredFields:  types.CoveredFields{WholeTransaction: true},
			})
			sigHash := txn.SigHash(int(j))
			sig, err := crypto.SignHash(sigHash, loadedKeys[i].SecretKey)
			if err != nil {
				return err
			}
			txn.TransactionSignatures[j].Signature = sig[:]
			i++
			j++
		}
		err := txn.StandaloneValid(0)
		if err != nil {
			return err
		}
		txn.TransactionSignatures = nil
	}
	return nil
}

// negotiateRevision sends the revision and new piece data to the host.
func negotiateRevision(conn net.Conn, rev types.FileContractRevision, piece []byte, secretKey crypto.SecretKey) (types.Transaction, error) {
	conn.SetDeadline(time.Now().Add(5 * time.Minute)) // sufficient to transfer 4 MB over 100 kbps
	defer conn.SetDeadline(time.Time{})               // reset timeout after each revision

	// create transaction containing the revision
	signedTxn := types.Transaction{
		FileContractRevisions: []types.FileContractRevision{rev},
		TransactionSignatures: []types.TransactionSignature{{
			ParentID:       crypto.Hash(rev.ParentID),
			CoveredFields:  types.CoveredFields{FileContractRevisions: []uint64{0}},
			PublicKeyIndex: 0, // renter key is always first -- see negotiateContract
		}},
	}
	// sign the transaction
	encodedSig, _ := crypto.SignHash(signedTxn.SigHash(0), secretKey) // no error possible
	signedTxn.TransactionSignatures[0].Signature = encodedSig[:]

	// send the transaction
	if err := encoding.WriteObject(conn, signedTxn); err != nil {
		return types.Transaction{}, errors.New("couldn't send revision transaction: " + err.Error())
	}

	// host sends acceptance
	var response string
	if err := encoding.ReadObject(conn, &response, 128); err != nil {
		return types.Transaction{}, errors.New("couldn't read host acceptance: " + err.Error())
	}
	if response != modules.AcceptResponse {
		return types.Transaction{}, errors.New("host rejected revision: " + response)
	}

	// transfer piece
	if _, err := conn.Write(piece); err != nil {
		return types.Transaction{}, errors.New("couldn't transfer piece: " + err.Error())
	}

	// read txn signed by host
	var signedHostTxn types.Transaction
	if err := encoding.ReadObject(conn, &signedHostTxn, types.BlockSizeLimit); err != nil {
		return types.Transaction{}, errors.New("couldn't read signed revision transaction: " + err.Error())
	}

	if signedHostTxn.ID() != signedTxn.ID() {
		return types.Transaction{}, errors.New("host sent bad signed transaction")
	}

	return signedHostTxn, nil
}

// addSignatures will sign a transaction using a spendable key, with support
// for multisig spendable keys. Because of the restricted input, the function
// is compatible with both siacoin inputs and siafund inputs.
func addSignatures(txn *types.Transaction, cf types.CoveredFields, uc types.UnlockConditions, parentID crypto.Hash, spendKey spendableKey) (newSigIndices []int, err error) {
	// Try to find the matching secret key for each public key - some public
	// keys may not have a match. Some secret keys may be used multiple times,
	// which is why public keys are used as the outer loop.
	totalSignatures := uint64(0)
	for i, siaPubKey := range uc.PublicKeys {
		// Search for the matching secret key to the public key.
		for j := range spendKey.SecretKeys {
			pubKey := spendKey.SecretKeys[j].PublicKey()
			if bytes.Compare(siaPubKey.Key, pubKey[:]) != 0 {
				continue
			}

			// Found the right secret key, add a signature.
			sig := types.TransactionSignature{
				ParentID:       parentID,
				CoveredFields:  cf,
				PublicKeyIndex: uint64(i),
			}
			newSigIndices = append(newSigIndices, len(txn.TransactionSignatures))
			txn.TransactionSignatures = append(txn.TransactionSignatures, sig)
			sigIndex := len(txn.TransactionSignatures) - 1
			sigHash := txn.SigHash(sigIndex)
			encodedSig, err := crypto.SignHash(sigHash, spendKey.SecretKeys[j])
			if err != nil {
				return nil, err
			}
			txn.TransactionSignatures[sigIndex].Signature = encodedSig[:]

			// Count that the signature has been added, and break out of the
			// secret key loop.
			totalSignatures++
			break
		}

		// If there are enough signatures to satisfy the unlock conditions,
		// break out of the outer loop.
		if totalSignatures == uc.SignaturesRequired {
			break
		}
	}
	return newSigIndices, nil
}

// addSignatures will sign a transaction using a spendable key, with support
// for multisig spendable keys. Because of the restricted input, the function
// is compatible with both siacoin inputs and siafund inputs.
func addSignatures(txn *types.Transaction, cf types.CoveredFields, uc types.UnlockConditions, parentID crypto.Hash, key spendableKey) error {
	usedIndices := make(map[int]struct{})
	for i := range key.secretKeys {
		found := false
		keyIndex := 0
		pubKey := key.secretKeys[i].PublicKey()
		for i, siaPublicKey := range uc.PublicKeys {
			_, exists := usedIndices[i]
			if !exists && bytes.Compare(pubKey[:], siaPublicKey.Key) == 0 {
				found = true
				keyIndex = i
				break
			}
		}
		if !found && build.DEBUG {
			panic("transaction builder cannot sign an input that it added")
		}
		usedIndices[keyIndex] = struct{}{}

		// Create the unsigned transaction signature.
		sig := types.TransactionSignature{
			ParentID:       parentID,
			CoveredFields:  cf,
			PublicKeyIndex: uint64(keyIndex),
		}
		txn.TransactionSignatures = append(txn.TransactionSignatures, sig)

		// Get the signature.
		sigIndex := len(txn.TransactionSignatures) - 1
		sigHash := txn.SigHash(sigIndex)
		encodedSig, err := crypto.SignHash(sigHash, key.secretKeys[i])
		if err != nil {
			return err
		}
		txn.TransactionSignatures[sigIndex].Signature = encodedSig[:]
	}
	return nil
}

// createRevisionSignature creates a signature for a file contract revision
// that signs on the file contract revision. The renter should have already
// provided the signature. createRevisionSignature will check to make sure that
// the renter's signature is valid.
func createRevisionSignature(fcr types.FileContractRevision, renterSig types.TransactionSignature, secretKey crypto.SecretKey, blockHeight types.BlockHeight) (types.Transaction, error) {
	hostSig := types.TransactionSignature{
		ParentID:       crypto.Hash(fcr.ParentID),
		PublicKeyIndex: 1,
		CoveredFields: types.CoveredFields{
			FileContractRevisions: []uint64{0},
		},
	}
	txn := types.Transaction{
		FileContractRevisions: []types.FileContractRevision{fcr},
		TransactionSignatures: []types.TransactionSignature{renterSig, hostSig},
	}
	sigHash := txn.SigHash(1)
	encodedSig, err := crypto.SignHash(sigHash, secretKey)
	if err != nil {
		return types.Transaction{}, err
	}
	txn.TransactionSignatures[1].Signature = encodedSig[:]
	err = modules.VerifyFileContractRevisionTransactionSignatures(fcr, txn.TransactionSignatures, blockHeight)
	if err != nil {
		return types.Transaction{}, err
	}
	return txn, nil
}

//.........這裏部分代碼省略.........

	// accept new revisions in a loop. The final good transaction will be
	// submitted to the blockchain.
	revisionErr := func() error {
		for {
			// allow 5 minutes between revisions
			err := conn.SetDeadline(time.Now().Add(5 * time.Minute))
			if err != nil {
				return err
			}

			// read proposed revision
			var revTxn types.Transaction
			if err = encoding.ReadObject(conn, &revTxn, types.BlockSizeLimit); err != nil {
				return errors.New("couldn't read revision: " + err.Error())
			}
			// an empty transaction indicates completion
			if revTxn.ID() == (types.Transaction{}).ID() {
				return nil
			}

			// allow 5 minutes for each revision
			err = conn.SetDeadline(time.Now().Add(5 * time.Minute))
			if err != nil {
				return err
			}

			// check revision against original file contract
			h.mu.RLock()
			err = h.considerRevision(revTxn, obligation)
			h.mu.RUnlock()
			if err != nil {
				// There is nothing that can be done if there is an error while
				// writing to a connection.
				_ = encoding.WriteObject(conn, err.Error())
				return err
			}

			// indicate acceptance
			if err := encoding.WriteObject(conn, modules.AcceptResponse); err != nil {
				return errors.New("couldn't write acceptance: " + err.Error())
			}

			// read piece
			// TODO: simultaneously read into tree and file
			rev := revTxn.FileContractRevisions[0]
			piece := make([]byte, rev.NewFileSize-obligation.fileSize())
			_, err = io.ReadFull(conn, piece)
			if err != nil {
				return errors.New("couldn't read piece data: " + err.Error())
			}

			// verify Merkle root
			err = tree.ReadSegments(bytes.NewReader(piece))
			if err != nil {
				return errors.New("couldn't verify Merkle root: " + err.Error())
			}
			if tree.Root() != rev.NewFileMerkleRoot {
				return errors.New("revision has bad Merkle root")
			}

			// manually sign the transaction
			revTxn.TransactionSignatures = append(revTxn.TransactionSignatures, types.TransactionSignature{
				ParentID:       crypto.Hash(fcid),
				CoveredFields:  types.CoveredFields{FileContractRevisions: []uint64{0}},
				PublicKeyIndex: 1, // host key is always second
			})
			encodedSig, err := crypto.SignHash(revTxn.SigHash(1), h.secretKey)
			if err != nil {
				return err
			}
			revTxn.TransactionSignatures[1].Signature = encodedSig[:]

			// append piece to file
			if _, err := file.Write(piece); err != nil {
				return errors.New("couldn't write new data to file: " + err.Error())
			}

			// save updated obligation to disk
			h.mu.Lock()
			h.reviseObligation(revTxn)
			h.mu.Unlock()

			// send the signed transaction - this must be the last thing that happens.
			if err := encoding.WriteObject(conn, revTxn); err != nil {
				return errors.New("couldn't write signed revision transaction: " + err.Error())
			}
		}
	}()
	err = file.Close()
	if err != nil {
		return err
	}

	err = h.tpool.AcceptTransactionSet([]types.Transaction{obligation.RevisionTransaction})
	if err != nil {
		h.log.Println("WARN: transaction pool rejected revision transaction: " + err.Error())
	}
	return revisionErr
}

//.........這裏部分代碼省略.........
	// sign the txn
	signedTxnSet, err := txnBuilder.Sign(true)
	if err != nil {
		return modules.RenterContract{}, modules.WriteNegotiationRejection(conn, errors.New("failed to sign transaction: "+err.Error()))
	}

	// calculate signatures added by the transaction builder
	var addedSignatures []types.TransactionSignature
	_, _, _, addedSignatureIndices := txnBuilder.ViewAdded()
	for _, i := range addedSignatureIndices {
		addedSignatures = append(addedSignatures, signedTxnSet[len(signedTxnSet)-1].TransactionSignatures[i])
	}

	// create initial (no-op) revision, transaction, and signature
	initRevision := types.FileContractRevision{
		ParentID:          signedTxnSet[len(signedTxnSet)-1].FileContractID(0),
		UnlockConditions:  contract.LastRevision.UnlockConditions,
		NewRevisionNumber: 1,

		NewFileSize:           fc.FileSize,
		NewFileMerkleRoot:     fc.FileMerkleRoot,
		NewWindowStart:        fc.WindowStart,
		NewWindowEnd:          fc.WindowEnd,
		NewValidProofOutputs:  fc.ValidProofOutputs,
		NewMissedProofOutputs: fc.MissedProofOutputs,
		NewUnlockHash:         fc.UnlockHash,
	}
	renterRevisionSig := types.TransactionSignature{
		ParentID:       crypto.Hash(initRevision.ParentID),
		PublicKeyIndex: 0,
		CoveredFields: types.CoveredFields{
			FileContractRevisions: []uint64{0},
		},
	}
	revisionTxn := types.Transaction{
		FileContractRevisions: []types.FileContractRevision{initRevision},
		TransactionSignatures: []types.TransactionSignature{renterRevisionSig},
	}
	encodedSig, err := crypto.SignHash(revisionTxn.SigHash(0), ourSK)
	if err != nil {
		return modules.RenterContract{}, modules.WriteNegotiationRejection(conn, errors.New("failed to sign revision transaction: "+err.Error()))
	}
	revisionTxn.TransactionSignatures[0].Signature = encodedSig[:]

	// Send acceptance and signatures
	if err = modules.WriteNegotiationAcceptance(conn); err != nil {
		return modules.RenterContract{}, errors.New("couldn't send transaction acceptance: " + err.Error())
	}
	if err = encoding.WriteObject(conn, addedSignatures); err != nil {
		return modules.RenterContract{}, errors.New("couldn't send added signatures: " + err.Error())
	}
	if err = encoding.WriteObject(conn, revisionTxn.TransactionSignatures[0]); err != nil {
		return modules.RenterContract{}, errors.New("couldn't send revision signature: " + err.Error())
	}

	// Read the host acceptance and signatures.
	err = modules.ReadNegotiationAcceptance(conn)
	if err != nil {
		return modules.RenterContract{}, errors.New("host did not accept our signatures: " + err.Error())
	}
	var hostSigs []types.TransactionSignature
	if err = encoding.ReadObject(conn, &hostSigs, 2e3); err != nil {
		return modules.RenterContract{}, errors.New("couldn't read the host's signatures: " + err.Error())
	}
	for _, sig := range hostSigs {
		txnBuilder.AddTransactionSignature(sig)
	}
	var hostRevisionSig types.TransactionSignature
	if err = encoding.ReadObject(conn, &hostRevisionSig, 2e3); err != nil {
		return modules.RenterContract{}, errors.New("couldn't read the host's revision signature: " + err.Error())
	}
	revisionTxn.TransactionSignatures = append(revisionTxn.TransactionSignatures, hostRevisionSig)

	// Construct the final transaction.
	txn, parentTxns = txnBuilder.View()
	txnSet = append(parentTxns, txn)

	// Submit to blockchain.
	err = tpool.AcceptTransactionSet(txnSet)
	if err == modules.ErrDuplicateTransactionSet {
		// as long as it made it into the transaction pool, we're good
		err = nil
	}
	if err != nil {
		return modules.RenterContract{}, err
	}

	// calculate contract ID
	fcid := txn.FileContractID(0)

	return modules.RenterContract{
		FileContract:    fc,
		ID:              fcid,
		LastRevision:    initRevision,
		LastRevisionTxn: revisionTxn,
		MerkleRoots:     contract.MerkleRoots,
		NetAddress:      host.NetAddress,
		SecretKey:       ourSK,
	}, nil
}

func TestReviseContract(t *testing.T) {
	if testing.Short() {
		t.SkipNow()
	}
	t.Parallel()
	ct, err := newContractorTester("TestReviseContract")
	if err != nil {
		t.Fatal(err)
	}

	// get an address
	ourAddr, err := ct.wallet.NextAddress()
	if err != nil {
		t.Fatal(err)
	}

	// generate keys
	sk, pk, err := crypto.GenerateKeyPair()
	if err != nil {
		t.Fatal(err)
	}
	renterPubKey := types.SiaPublicKey{
		Algorithm: types.SignatureEd25519,
		Key:       pk[:],
	}

	uc := types.UnlockConditions{
		PublicKeys:         []types.SiaPublicKey{renterPubKey, renterPubKey},
		SignaturesRequired: 1,
	}

	// create file contract
	payout := types.NewCurrency64(1e16)

	fc := types.FileContract{
		FileSize:       0,
		FileMerkleRoot: crypto.Hash{}, // no proof possible without data
		WindowStart:    100,
		WindowEnd:      1000,
		Payout:         payout,
		UnlockHash:     uc.UnlockHash(),
		RevisionNumber: 0,
	}
	// outputs need account for tax
	fc.ValidProofOutputs = []types.SiacoinOutput{
		{Value: types.PostTax(ct.contractor.blockHeight, payout), UnlockHash: ourAddr.UnlockHash()},
		{Value: types.ZeroCurrency, UnlockHash: types.UnlockHash{}}, // no collateral
	}
	fc.MissedProofOutputs = []types.SiacoinOutput{
		// same as above
		fc.ValidProofOutputs[0],
		// goes to the void, not the hostdb
		{Value: types.ZeroCurrency, UnlockHash: types.UnlockHash{}},
	}

	txnBuilder := ct.wallet.StartTransaction()
	err = txnBuilder.FundSiacoins(fc.Payout)
	if err != nil {
		t.Fatal(err)
	}
	txnBuilder.AddFileContract(fc)
	signedTxnSet, err := txnBuilder.Sign(true)
	if err != nil {
		t.Fatal(err)
	}

	// submit contract
	err = ct.tpool.AcceptTransactionSet(signedTxnSet)
	if err != nil {
		t.Fatal(err)
	}

	// create revision
	fcid := signedTxnSet[len(signedTxnSet)-1].FileContractID(0)
	rev := types.FileContractRevision{
		ParentID:              fcid,
		UnlockConditions:      uc,
		NewFileSize:           10,
		NewWindowStart:        100,
		NewWindowEnd:          1000,
		NewRevisionNumber:     1,
		NewValidProofOutputs:  fc.ValidProofOutputs,
		NewMissedProofOutputs: fc.MissedProofOutputs,
	}

	// create transaction containing the revision
	signedTxn := types.Transaction{
		FileContractRevisions: []types.FileContractRevision{rev},
		TransactionSignatures: []types.TransactionSignature{{
			ParentID:       crypto.Hash(fcid),
			CoveredFields:  types.CoveredFields{FileContractRevisions: []uint64{0}},
			PublicKeyIndex: 0, // hostdb key is always first -- see negotiateContract
		}},
	}

	// sign the transaction
	encodedSig, err := crypto.SignHash(signedTxn.SigHash(0), sk)
	if err != nil {
		t.Fatal(err)
	}
//.........這裏部分代碼省略.........

// revise revises fc to cover piece and uploads both the revision and the
// piece data to the host.
func (hu *hostUploader) revise(fc types.FileContract, piece []byte, height types.BlockHeight) error {
	hu.conn.SetDeadline(time.Now().Add(5 * time.Minute)) // sufficient to transfer 4 MB over 100 kbps
	defer hu.conn.SetDeadline(time.Time{})               // reset timeout after each revision

	// calculate new merkle root
	err := hu.tree.ReadSegments(bytes.NewReader(piece))
	if err != nil {
		return err
	}

	// create revision
	rev := types.FileContractRevision{
		ParentID:          hu.contract.ID,
		UnlockConditions:  hu.unlockConditions,
		NewRevisionNumber: fc.RevisionNumber + 1,

		NewFileSize:           fc.FileSize + uint64(len(piece)),
		NewFileMerkleRoot:     hu.tree.Root(),
		NewWindowStart:        fc.WindowStart,
		NewWindowEnd:          fc.WindowEnd,
		NewValidProofOutputs:  fc.ValidProofOutputs,
		NewMissedProofOutputs: fc.MissedProofOutputs,
		NewUnlockHash:         fc.UnlockHash,
	}
	// transfer value of piece from renter to host
	safeDuration := uint64(fc.WindowStart - height + 20) // buffer in case host is behind
	piecePrice := types.NewCurrency64(uint64(len(piece))).Mul(types.NewCurrency64(safeDuration)).Mul(hu.settings.Price)
	// prevent a negative currency panic
	if piecePrice.Cmp(fc.ValidProofOutputs[0].Value) > 0 {
		// probably not enough money, but the host might accept it anyway
		piecePrice = fc.ValidProofOutputs[0].Value
	}
	rev.NewValidProofOutputs[0].Value = rev.NewValidProofOutputs[0].Value.Sub(piecePrice)   // less returned to renter
	rev.NewValidProofOutputs[1].Value = rev.NewValidProofOutputs[1].Value.Add(piecePrice)   // more given to host
	rev.NewMissedProofOutputs[0].Value = rev.NewMissedProofOutputs[0].Value.Sub(piecePrice) // less returned to renter
	rev.NewMissedProofOutputs[1].Value = rev.NewMissedProofOutputs[1].Value.Add(piecePrice) // more given to void

	// create transaction containing the revision
	signedTxn := types.Transaction{
		FileContractRevisions: []types.FileContractRevision{rev},
		TransactionSignatures: []types.TransactionSignature{{
			ParentID:       crypto.Hash(hu.contract.ID),
			CoveredFields:  types.CoveredFields{FileContractRevisions: []uint64{0}},
			PublicKeyIndex: 0, // renter key is always first -- see negotiateContract
		}},
	}

	// sign the transaction
	encodedSig, err := crypto.SignHash(signedTxn.SigHash(0), hu.secretKey)
	if err != nil {
		return err
	}
	signedTxn.TransactionSignatures[0].Signature = encodedSig[:]

	// send the transaction
	if err := encoding.WriteObject(hu.conn, signedTxn); err != nil {
		return err
	}

	// host sends acceptance
	var response string
	if err := encoding.ReadObject(hu.conn, &response, 128); err != nil {
		return err
	}
	if response != modules.AcceptResponse {
		return errors.New("host rejected revision: " + response)
	}

	// transfer piece
	if _, err := hu.conn.Write(piece); err != nil {
		return err
	}

	// read txn signed by host
	var signedHostTxn types.Transaction
	if err := encoding.ReadObject(hu.conn, &signedHostTxn, types.BlockSizeLimit); err != nil {
		return err
	}

	if signedHostTxn.ID() != signedTxn.ID() {
		return errors.New("host sent bad signed transaction")
	} else if err = signedHostTxn.StandaloneValid(height); err != nil {
		return err
	}

	hu.lastTxn = signedHostTxn

	return nil
}

// FundTransaction adds siacoins to a transaction that the wallet knows how to
// spend. The exact amount of coins are always added, and this is achieved by
// creating two transactions. The first transaciton, the parent, spends a set
// of outputs that add up to at least the desired amount, and then creates a
// single output of the exact amount and a second refund output.
func (w *Wallet) FundTransaction(id string, amount types.Currency) (t types.Transaction, err error) {
	counter := w.mu.Lock()
	defer w.mu.Unlock(counter)

	// Create a parent transaction and supply it with enough inputs to cover
	// 'amount'.
	parentTxn := types.Transaction{}
	fundingOutputs, fundingTotal, err := w.findOutputs(amount)
	if err != nil {
		return
	}
	for _, output := range fundingOutputs {
		output.age = w.age
		key := w.keys[output.output.UnlockHash]
		newInput := types.SiacoinInput{
			ParentID:         output.id,
			UnlockConditions: key.unlockConditions,
		}
		parentTxn.SiacoinInputs = append(parentTxn.SiacoinInputs, newInput)
	}

	// Create and add the output that will be used to fund the standard
	// transaction.
	parentDest, parentSpendConds, err := w.coinAddress(false) // false indicates that the address should not be visible to the user
	exactOutput := types.SiacoinOutput{
		Value:      amount,
		UnlockHash: parentDest,
	}
	parentTxn.SiacoinOutputs = append(parentTxn.SiacoinOutputs, exactOutput)

	// Create a refund output if needed.
	if amount.Cmp(fundingTotal) != 0 {
		var refundDest types.UnlockHash
		refundDest, _, err = w.coinAddress(false) // false indicates that the address should not be visible to the user
		if err != nil {
			return
		}
		refundOutput := types.SiacoinOutput{
			Value:      fundingTotal.Sub(amount),
			UnlockHash: refundDest,
		}
		parentTxn.SiacoinOutputs = append(parentTxn.SiacoinOutputs, refundOutput)
	}

	// Sign all of the inputs to the parent trancstion.
	coveredFields := types.CoveredFields{WholeTransaction: true}
	for _, input := range parentTxn.SiacoinInputs {
		sig := types.TransactionSignature{
			ParentID:       crypto.Hash(input.ParentID),
			CoveredFields:  coveredFields,
			PublicKeyIndex: 0,
		}
		parentTxn.TransactionSignatures = append(parentTxn.TransactionSignatures, sig)

		// Hash the transaction according to the covered fields.
		coinAddress := input.UnlockConditions.UnlockHash()
		sigIndex := len(parentTxn.TransactionSignatures) - 1
		secKey := w.keys[coinAddress].secretKey
		sigHash := parentTxn.SigHash(sigIndex)

		// Get the signature.
		var encodedSig crypto.Signature
		encodedSig, err = crypto.SignHash(sigHash, secKey)
		if err != nil {
			return
		}
		parentTxn.TransactionSignatures[sigIndex].Signature = types.Signature(encodedSig[:])
	}

	// Add the exact output to the wallet's knowledgebase before releasing the
	// lock, to prevent the wallet from using the exact output elsewhere.
	key := w.keys[parentSpendConds.UnlockHash()]
	key.outputs[parentTxn.SiacoinOutputID(0)] = &knownOutput{
		id:     parentTxn.SiacoinOutputID(0),
		output: exactOutput,

		spendable: true,
		age:       w.age,
	}

	// Send the transaction to the transaction pool.
	err = w.tpool.AcceptTransaction(parentTxn)
	if err != nil {
		return
	}

	// Get the transaction that was originally meant to be funded.
	openTxn, exists := w.transactions[id]
	if !exists {
		err = ErrInvalidID
		return
	}
	txn := openTxn.transaction

	// Add the exact output.
//.........這裏部分代碼省略.........

//.........這裏部分代碼省略.........
			UnlockHash: types.UnlockHash{},
			Value:      types.PostTax(cst.cs.dbBlockHeight(), payout),
		}},
		UnlockHash: uc.UnlockHash(),
	}

	// Submit a transaction with the file contract.
	txnBuilder := cst.wallet.StartTransaction()
	err = txnBuilder.FundSiacoins(payout)
	if err != nil {
		panic(err)
	}
	fcIndex := txnBuilder.AddFileContract(fc)
	txnSet, err := txnBuilder.Sign(true)
	if err != nil {
		panic(err)
	}
	err = cst.tpool.AcceptTransactionSet(txnSet)
	if err != nil {
		panic(err)
	}
	_, err = cst.miner.AddBlock()
	if err != nil {
		panic(err)
	}

	// Submit a revision for the file contract.
	ti := len(txnSet) - 1
	fcid := txnSet[ti].FileContractID(fcIndex)
	fcr := types.FileContractRevision{
		ParentID:          fcid,
		UnlockConditions:  uc,
		NewRevisionNumber: 69292,

		NewFileSize:           filesize,
		NewFileMerkleRoot:     merkleRoot,
		NewWindowStart:        cst.cs.dbBlockHeight() + 1,
		NewWindowEnd:          cst.cs.dbBlockHeight() + 2,
		NewValidProofOutputs:  fc.ValidProofOutputs,
		NewMissedProofOutputs: fc.MissedProofOutputs,
		NewUnlockHash:         uc.UnlockHash(),
	}
	ts := types.TransactionSignature{
		ParentID:       crypto.Hash(fcid),
		CoveredFields:  types.CoveredFields{WholeTransaction: true},
		PublicKeyIndex: 0,
	}
	txn := types.Transaction{
		FileContractRevisions: []types.FileContractRevision{fcr},
		TransactionSignatures: []types.TransactionSignature{ts},
	}
	encodedSig, err := crypto.SignHash(txn.SigHash(0), sk)
	if err != nil {
		panic(err)
	}
	txn.TransactionSignatures[0].Signature = encodedSig[:]
	err = cst.tpool.AcceptTransactionSet([]types.Transaction{txn})
	if err != nil {
		panic(err)
	}
	_, err = cst.miner.AddBlock()
	if err != nil {
		panic(err)
	}

	// Create and submit a storage proof for the file contract.
	segmentIndex, err := cst.cs.StorageProofSegment(fcid)
	if err != nil {
		panic(err)
	}
	segment, hashSet, err := crypto.BuildReaderProof(file, segmentIndex)
	if err != nil {
		panic(err)
	}
	sp := types.StorageProof{
		ParentID: fcid,
		HashSet:  hashSet,
	}
	copy(sp.Segment[:], segment)
	txnBuilder = cst.wallet.StartTransaction()
	txnBuilder.AddStorageProof(sp)
	txnSet, err = txnBuilder.Sign(true)
	if err != nil {
		panic(err)
	}
	err = cst.tpool.AcceptTransactionSet(txnSet)
	if err != nil {
		panic(err)
	}
	_, err = cst.miner.AddBlock()
	if err != nil {
		panic(err)
	}

	// Check that the file contract has been removed.
	_, err = cst.cs.dbGetFileContract(fcid)
	if err != errNilItem {
		panic("file contract should not exist in the database")
	}
}

//.........這裏部分代碼省略.........
	}

	// accept new revisions in a loop. The final good transaction will be
	// submitted to the blockchain.
	var finalTxn types.Transaction
	defer func() {
		h.tpool.AcceptTransactionSet([]types.Transaction{finalTxn})
	}()
	for {
		// read proposed revision
		var revTxn types.Transaction
		if err := encoding.ReadObject(conn, &revTxn, types.BlockSizeLimit); err != nil {
			return err
		}
		// an empty transaction indicates completion
		if revTxn.ID() == (types.Transaction{}).ID() {
			break
		}

		// check revision against original file contract
		lockID = h.mu.RLock()
		err := h.considerRevision(revTxn, obligation)
		h.mu.RUnlock(lockID)
		if err != nil {
			encoding.WriteObject(conn, err.Error())
			continue // don't terminate loop; subsequent revisions may be okay
		}

		// indicate acceptance
		if err := encoding.WriteObject(conn, modules.AcceptResponse); err != nil {
			return err
		}

		// read piece
		// TODO: simultaneously read into tree?
		rev := revTxn.FileContractRevisions[0]
		piece := make([]byte, rev.NewFileSize-obligation.FileContract.FileSize)
		_, err = io.ReadFull(conn, piece)
		if err != nil {
			return err
		}

		// verify Merkle root
		r := bytes.NewReader(piece)
		for {
			_, err := io.ReadFull(r, buf)
			if err == io.EOF {
				break
			} else if err != nil && err != io.ErrUnexpectedEOF {
				return err
			}
			tree.Push(buf)
		}
		if tree.Root() != rev.NewFileMerkleRoot {
			return errors.New("revision has bad Merkle root")
		}

		// manually sign the transaction
		revTxn.TransactionSignatures = append(revTxn.TransactionSignatures, types.TransactionSignature{
			ParentID:       crypto.Hash(fcid),
			CoveredFields:  types.CoveredFields{FileContractRevisions: []uint64{0}},
			PublicKeyIndex: 1, // host key is always second
		})
		encodedSig, err := crypto.SignHash(revTxn.SigHash(1), h.secretKey)
		if err != nil {
			return err
		}
		revTxn.TransactionSignatures[1].Signature = encodedSig[:]

		// send the signed transaction
		if err := encoding.WriteObject(conn, revTxn); err != nil {
			return err
		}

		// append piece to file
		if _, err := file.Write(piece); err != nil {
			return err
		}

		// save updated obligation to disk
		lockID = h.mu.Lock()
		h.spaceRemaining -= int64(len(piece))
		obligation.FileContract.RevisionNumber = rev.NewRevisionNumber
		obligation.FileContract.FileSize = rev.NewFileSize
		obligation.FileContract.FileMerkleRoot = rev.NewFileMerkleRoot
		h.obligationsByID[obligation.ID] = obligation
		heightObligations := h.obligationsByHeight[obligation.FileContract.WindowStart+StorageProofReorgDepth]
		for i := range heightObligations {
			if heightObligations[i].ID == obligation.ID {
				heightObligations[i] = obligation
			}
		}
		h.save()
		h.mu.Unlock(lockID)

		finalTxn = revTxn
	}

	return nil
}

// verifyKeys checks a set of keys on disk to see that they can spend funds
// sent to their address.
func verifyKeys(uc types.UnlockConditions, folder string, keyname string) error {
	keysRequired := uc.SignaturesRequired
	totalKeys := uint64(len(uc.PublicKeys))

	// Load the keys from disk back into memory, then verify that the keys on
	// disk are able to sign outputs in transactions.
	loadedKeys := make([]KeyPair, totalKeys)
	for i := 0; i < len(loadedKeys); i++ {
		err := encoding.ReadFile(filepath.Join(folder, keyname+"_Key"+strconv.Itoa(i)+FileExtension), &loadedKeys[i])
		if err != nil {
			return err
		}
		if loadedKeys[i].Header != FileHeader {
			return ErrUnknownHeader
		}
		if loadedKeys[i].Version != FileVersion {
			return ErrUnknownVersion
		}
	}

	// Check that the keys can be used to spend transactions.
	for _, loadedKey := range loadedKeys {
		if loadedKey.UnlockConditions.UnlockHash() != uc.UnlockHash() {
			return ErrCorruptedKey
		}
	}
	// Create a transaction for the keys to sign.
	txn := types.Transaction{
		SiafundInputs: []types.SiafundInput{
			types.SiafundInput{
				UnlockConditions: loadedKeys[0].UnlockConditions,
			},
		},
	}
	// Loop through and sign the transaction multiple times. All keys will be
	// used at least once by the time the loop terminates.
	var i uint64
	for i != totalKeys {
		// i tracks which key is next to be used. If i + RequiredKeys results
		// in going out-of-bounds, reduce i so that the last key will be used
		// for the final signature.
		if i+keysRequired > totalKeys {
			i = totalKeys - keysRequired
		}
		var j uint64
		for j < keysRequired {
			txn.TransactionSignatures = append(txn.TransactionSignatures, types.TransactionSignature{
				PublicKeyIndex: i,
				CoveredFields:  types.CoveredFields{WholeTransaction: true},
			})
			sigHash := txn.SigHash(int(j))
			sig, err := crypto.SignHash(sigHash, loadedKeys[i].SecretKey)
			if err != nil {
				return err
			}
			txn.TransactionSignatures[j].Signature = sig[:]
			i++
			j++
		}
		// Check that the signature is valid.
		err := txn.StandaloneValid(0)
		if err != nil {
			return err
		}
		// Delete all of the signatures for the next iteration.
		txn.TransactionSignatures = nil
	}
	return nil
}

//.........這裏部分代碼省略.........

	// sign the txn
	signedTxnSet, err := txnBuilder.Sign(true)
	if err != nil {
		return modules.RenterContract{}, modules.WriteNegotiationRejection(conn, errors.New("failed to sign transaction: "+err.Error()))
	}

	// calculate signatures added by the transaction builder
	var addedSignatures []types.TransactionSignature
	_, _, _, addedSignatureIndices := txnBuilder.ViewAdded()
	for _, i := range addedSignatureIndices {
		addedSignatures = append(addedSignatures, signedTxnSet[len(signedTxnSet)-1].TransactionSignatures[i])
	}

	// create initial (no-op) revision, transaction, and signature
	initRevision := types.FileContractRevision{
		ParentID:          signedTxnSet[len(signedTxnSet)-1].FileContractID(0),
		UnlockConditions:  uc,
		NewRevisionNumber: 1,

		NewFileSize:           fc.FileSize,
		NewFileMerkleRoot:     fc.FileMerkleRoot,
		NewWindowStart:        fc.WindowStart,
		NewWindowEnd:          fc.WindowEnd,
		NewValidProofOutputs:  fc.ValidProofOutputs,
		NewMissedProofOutputs: fc.MissedProofOutputs,
		NewUnlockHash:         fc.UnlockHash,
	}
	renterRevisionSig := types.TransactionSignature{
		ParentID:       crypto.Hash(initRevision.ParentID),
		PublicKeyIndex: 0,
		CoveredFields: types.CoveredFields{
			FileContractRevisions: []uint64{0},
		},
	}
	revisionTxn := types.Transaction{
		FileContractRevisions: []types.FileContractRevision{initRevision},
		TransactionSignatures: []types.TransactionSignature{renterRevisionSig},
	}
	encodedSig, err := crypto.SignHash(revisionTxn.SigHash(0), ourSK)
	if err != nil {
		return modules.RenterContract{}, modules.WriteNegotiationRejection(conn, errors.New("failed to sign revision transaction: "+err.Error()))
	}
	revisionTxn.TransactionSignatures[0].Signature = encodedSig[:]

	// Send acceptance and signatures
	if err = modules.WriteNegotiationAcceptance(conn); err != nil {
		return modules.RenterContract{}, errors.New("couldn't send transaction acceptance: " + err.Error())
	}
	if err = encoding.WriteObject(conn, addedSignatures); err != nil {
		return modules.RenterContract{}, errors.New("couldn't send added signatures: " + err.Error())
	}
	if err = encoding.WriteObject(conn, revisionTxn.TransactionSignatures[0]); err != nil {
		return modules.RenterContract{}, errors.New("couldn't send revision signature: " + err.Error())
	}

	// Read the host acceptance and signatures.
	err = modules.ReadNegotiationAcceptance(conn)
	if err != nil {
		return modules.RenterContract{}, errors.New("host did not accept our signatures: " + err.Error())
	}
	var hostSigs []types.TransactionSignature
	if err = encoding.ReadObject(conn, &hostSigs, 2e3); err != nil {
		return modules.RenterContract{}, errors.New("couldn't read the host's signatures: " + err.Error())
	}
	for _, sig := range hostSigs {
		txnBuilder.AddTransactionSignature(sig)
	}
	var hostRevisionSig types.TransactionSignature
	if err = encoding.ReadObject(conn, &hostRevisionSig, 2e3); err != nil {
		return modules.RenterContract{}, errors.New("couldn't read the host's revision signature: " + err.Error())
	}
	revisionTxn.TransactionSignatures = append(revisionTxn.TransactionSignatures, hostRevisionSig)

	// Construct the final transaction.
	txn, parentTxns = txnBuilder.View()
	txnSet = append(parentTxns, txn)

	// Submit to blockchain.
	err = tpool.AcceptTransactionSet(txnSet)
	if err == modules.ErrDuplicateTransactionSet {
		// as long as it made it into the transaction pool, we're good
		err = nil
	}
	if err != nil {
		return modules.RenterContract{}, err
	}

	// calculate contract ID
	fcid := txn.FileContractID(0)

	return modules.RenterContract{
		FileContract:    fc,
		ID:              fcid,
		LastRevision:    initRevision,
		LastRevisionTxn: revisionTxn,
		NetAddress:      host.NetAddress,
		SecretKey:       ourSK,
	}, nil
}