xmr: live refresh and get_tx_key added

- get_tx_key supports retrieval of private tx keys - required by users to check the transaction or when resolving disputes with the decipient
- get_tx_key supports to return transaction derivations = private tx key * public view key. This enables to compute tx_proof for outgoing transactions which is also a nice tool when resolving disputes, provides better protection as tx private key is hidden.
- live refresh enables computation of key images on the fly during the refresh. This helps to completely avoid key image sync and enables to use the Trezor with untrusted node.

protob/messages-monero.proto

@@ -385,6 +385,88 @@ message MoneroKeyImageSyncFinalAck {
     optional bytes enc_key = 1;
 }
 
+/**
+ * Request: Decrypt tx private keys blob
+ * @next MoneroGetTxKeyAck
+ */
+message MoneroGetTxKeyRequest {
+    repeated uint32 address_n = 1;          // BIP-32 path to derive the key from master node
+    optional uint32 network_type = 2;       // Main-net / testnet / stagenet
+
+    optional bytes salt1 = 3;
+    optional bytes salt2 = 4;
+    optional bytes tx_enc_keys = 5;
+    optional bytes tx_prefix_hash = 6;
+    optional uint32 reason = 7;  // reason to display for user. e.g., tx_proof
+    optional bytes view_public_key = 8;   // addr for derivation
+}
+
+/**
+ * Response: Response with the re-encrypted private keys and derivations blob under view key
+ * @end
+ */
+message MoneroGetTxKeyAck {
+    optional bytes salt = 1;
+    optional bytes tx_keys = 2;
+    optional bytes tx_derivations = 3;
+}
+
+/**
+ * Request: Starts live refresh flow. Asks user permission, switches state
+ * @next MoneroLiveRefreshStartAck
+ */
+message MoneroLiveRefreshStartRequest {
+    repeated uint32 address_n = 1;          // BIP-32 path to derive the key from master node
+    optional uint32 network_type = 2;       // Main-net / testnet / stagenet
+}
+
+/**
+ * Response after user gave permission
+ * @next MoneroLiveRefreshStepRequest
+ * @next MoneroLiveRefreshFinalRequest
+ */
+message MoneroLiveRefreshStartAck {
+
+}
+
+/**
+ * Request: Request to compute a single key image during live sync
+ * @next MoneroLiveRefreshStepAck
+ */
+message MoneroLiveRefreshStepRequest {
+    optional bytes out_key = 1;
+    optional bytes recv_deriv = 2;
+    optional uint64 real_out_idx = 3;
+    optional uint32 sub_addr_major = 4;
+    optional uint32 sub_addr_minor = 5;
+}
+
+/**
+ * Response: Response with the encrypted key image + signature
+ * @next MoneroLiveRefreshStepRequest
+ * @next MoneroLiveRefreshFinishedRequest
+ */
+message MoneroLiveRefreshStepAck {
+    optional bytes salt = 1;
+    optional bytes key_image = 2;
+}
+
+/**
+ * Request: Request terminating live refresh mode.
+ * @next MoneroLiveRefreshFinishedAck
+ */
+message MoneroLiveRefreshFinalRequest {
+
+}
+
+/**
+ * Response: Response on termination of live refresh mode.
+ * @end
+ */
+message MoneroLiveRefreshFinalAck {
+
+}
+
 /**
  * Request: Universal Monero protocol implementation diagnosis request.
  * @start

protob/messages.proto

@@ -229,4 +229,12 @@ enum MessageType {
     MessageType_MoneroWatchKey = 543 [(wire_out) = true];
     MessageType_DebugMoneroDiagRequest = 546 [(wire_in) = true];
     MessageType_DebugMoneroDiagAck = 547 [(wire_out) = true];
+    MessageType_MoneroGetTxKeyRequest = 550 [(wire_in) = true];
+    MessageType_MoneroGetTxKeyAck = 551 [(wire_out) = true];
+    MessageType_MoneroLiveRefreshStartRequest = 552 [(wire_in) = true];
+    MessageType_MoneroLiveRefreshStartAck = 553 [(wire_out) = true];
+    MessageType_MoneroLiveRefreshStepRequest = 554 [(wire_in) = true];
+    MessageType_MoneroLiveRefreshStepAck = 555 [(wire_out) = true];
+    MessageType_MoneroLiveRefreshFinalRequest = 556 [(wire_in) = true];
+    MessageType_MoneroLiveRefreshFinalAck = 557 [(wire_out) = true];
 }