Spend proof

main.qml

@@ -764,7 +764,11 @@ ApplicationWindow {
                     ", address: ", address,
                     ", message: ", message);
 
-        var result = currentWallet.getTxProof(txid, address, message);
+        var result;
+        if (address.length > 0)
+            result = currentWallet.getTxProof(txid, address, message);
+        if (!result || result.startsWith("error|"))
+            result = currentWallet.getSpendProof(txid, message);
         informationPopup.title  = qsTr("Payment proof") + translationManager.emptyString;
         if (result.startsWith("error|")) {
             var errorString = result.split("|")[1];
@@ -786,12 +790,16 @@ ApplicationWindow {
                     ", message: ", message,
                     ", signature: ", signature);
 
-        var result = currentWallet.checkTxProof(txid, address, message, signature);
+        var result;
+        if (address.length > 0)
+            result = currentWallet.checkTxProof(txid, address, message, signature);
+        else
+            result = currentWallet.checkSpendProof(txid, message, signature);
         var results = result.split("|");
-        if (results.length == 5 && results[0] == "true") {
-            var good = results[1] == "true";
+        if (address.length > 0 && results.length == 5 && results[0] === "true") {
+            var good = results[1] === "true";
             var received = results[2];
-            var in_pool = results[3] == "true";
+            var in_pool = results[3] === "true";
             var confirmations = results[4];
 
             informationPopup.title  = qsTr("Payment proof check") + translationManager.emptyString;
@@ -812,6 +820,12 @@ ApplicationWindow {
                 informationPopup.text = qsTr("This address received nothing");
             }
         }
+        else if (results.length == 2 && results[0] === "true") {
+            var good = results[1] === "true";
+            informationPopup.title = qsTr("Payment proof check") + translationManager.emptyString;
+            informationPopup.icon = good ? StandardIcon.Information : StandardIcon.Critical;
+            informationPopup.text = good ? qsTr("Good signature") : qsTr("Bad signature");
+        }
         else {
             informationPopup.title  = qsTr("Error") + translationManager.emptyString;
             informationPopup.text = currentWallet.errorString;

pages/TxKey.qml

@@ -72,6 +72,10 @@ Rectangle {
             if ((signature.length - 9) % 132 != 0)
                 return false;
             return check256(signature, signature.length);
+        } else if (signature.startsWith("SpendProofV")) {
+            if ((signature.length - 12) % 88 != 0)
+                return false;
+            return check256(signature, signature.length);
         }
         return false;
     }
@@ -90,7 +94,8 @@ Rectangle {
         property int lineEditFontSize: 12
 
         Text {
-            text: qsTr("Generate a proof of your incoming/outgoing payment by supplying the transaction ID, the recipient address and an optional message:") + translationManager.emptyString
+            text: qsTr("Generate a proof of your incoming/outgoing payment by supplying the transaction ID, the recipient address and an optional message. \n" +
+                       "For the case of outgoing payments, you can get a 'Spend Proof' that proves the authorship of a transaction. In this case, you don't need to specify the recipient address.") + translationManager.emptyString
             wrapMode: Text.Wrap
             Layout.fillWidth: true;
         }
@@ -183,7 +188,7 @@ Rectangle {
             shadowPressedColor: "#B32D00"
             releasedColor: "#FF6C3C"
             pressedColor: "#FF4304"
-            enabled: checkTxID(getProofTxIdLine.text) && checkAddress(getProofAddressLine.text, appWindow.persistentSettings.testnet)
+            enabled: checkTxID(getProofTxIdLine.text) && (getProofAddressLine.text.length == 0 || checkAddress(getProofAddressLine.text, appWindow.persistentSettings.testnet))
             onClicked: {
                 console.log("getProof: Generate clicked: txid " + getProofTxIdLine.text + ", address " + getProofAddressLine.text + ", message: " + getProofMessageLine.text);
                 root.getProofClicked(getProofTxIdLine.text, getProofAddressLine.text, getProofMessageLine.text)
@@ -201,7 +206,8 @@ Rectangle {
         }
 
         Text {
-            text: qsTr("Verify that funds were paid to an address by supplying the transaction ID, the recipient address, the message used for signing and the signature:") + translationManager.emptyString
+            text: qsTr("Verify that funds were paid to an address by supplying the transaction ID, the recipient address, the message used for signing and the signature.\n" +
+                       "For the case with Spend Proof, you don't need to specify the recipient address.") + translationManager.emptyString
             wrapMode: Text.Wrap
             Layout.fillWidth: true;
         }
@@ -322,7 +328,7 @@ Rectangle {
             shadowPressedColor: "#B32D00"
             releasedColor: "#FF6C3C"
             pressedColor: "#FF4304"
-            enabled: checkTxID(checkProofTxIdLine.text) && checkAddress(checkProofAddressLine.text, appWindow.persistentSettings.testnet) && checkSignature(checkProofSignatureLine.text)
+            enabled: checkTxID(checkProofTxIdLine.text) && checkSignature(checkProofSignatureLine.text) && ((checkProofSignatureLine.text.startsWith("SpendProofV") && checkProofAddressLine.text.length == 0) || (!checkProofSignatureLine.text.startsWith("SpendProofV") && checkAddress(checkProofAddressLine.text, appWindow.persistentSettings.testnet)))
             onClicked: {
                 console.log("checkProof: Check clicked: txid " + checkProofTxIdLine.text + ", address " + checkProofAddressLine.text + ", message " + checkProofMessageLine.text + ", signature " + checkProofSignatureLine.text);
                 root.checkProofClicked(checkProofTxIdLine.text, checkProofAddressLine.text, checkProofMessageLine.text, checkProofSignatureLine.text)

src/libwalletqt/Wallet.cpp

@@ -523,6 +523,22 @@ QString Wallet::checkTxProof(const QString &txid, const QString &address, const
     return QString::fromStdString(result);
 }
 
+Q_INVOKABLE QString Wallet::getSpendProof(const QString &txid, const QString &message) const
+{
+    std::string result = m_walletImpl->getSpendProof(txid.toStdString(), message.toStdString());
+    if (result.empty())
+        result = "error|" + m_walletImpl->errorString();
+    return QString::fromStdString(result);
+}
+
+Q_INVOKABLE QString Wallet::checkSpendProof(const QString &txid, const QString &message, const QString &signature) const
+{
+    bool good;
+    bool success = m_walletImpl->checkSpendProof(txid.toStdString(), message.toStdString(), signature.toStdString(), good);
+    std::string result = std::string(success ? "true" : "false") + "|" + std::string(!success ? m_walletImpl->errorString() : good ? "true" : "false");
+    return QString::fromStdString(result);
+}
+
 QString Wallet::signMessage(const QString &message, bool filename) const
 {
   if (filename) {

src/libwalletqt/Wallet.h

@@ -235,6 +235,8 @@ public:
     Q_INVOKABLE QString checkTxKey(const QString &txid, const QString &tx_key, const QString &address);
     Q_INVOKABLE QString getTxProof(const QString &txid, const QString &address, const QString &message) const;
     Q_INVOKABLE QString checkTxProof(const QString &txid, const QString &address, const QString &message, const QString &signature);
+    Q_INVOKABLE QString getSpendProof(const QString &txid, const QString &message) const;
+    Q_INVOKABLE QString checkSpendProof(const QString &txid, const QString &message, const QString &signature) const;
     // Rescan spent outputs
     Q_INVOKABLE bool rescanSpent();