Add the possibility to export private view key for fast scan.

On client startup the device asks for authorization to export the private view key.
If user agree, the client hold the private view key allowing a fast blockchain scan.
If the user does not agree, the blockchain scan is fully done via the device.

src/device/device.hpp

@@ -78,6 +78,7 @@ namespace hw {
            return false;
     }
 
+
     class device {
     protected:
         std::string  name;
@@ -89,10 +90,12 @@ namespace hw {
         virtual ~device()   {}
 
         explicit virtual operator bool() const = 0;
-
+        enum device_mode {
-        static const int SIGNATURE_REAL = 0;
+            NONE,
-        static const int SIGNATURE_FAKE = 1;
+            TRANSACTION_CREATE_REAL,
-
+            TRANSACTION_CREATE_FAKE,
+            TRANSACTION_PARSE
+        };
 
         /* ======================================================================= */
         /*                              SETUP/TEARDOWN                             */
@@ -106,6 +109,9 @@ namespace hw {
         virtual bool connect(void) = 0;
         virtual bool disconnect(void) = 0;
 
+        virtual bool  set_mode(device_mode mode) = 0;
+
+
         /* ======================================================================= */
         /*  LOCKER                                                                 */
         /* ======================================================================= */ 

src/device/device_default.cpp

@@ -82,6 +82,9 @@ namespace hw {
             dfns();
         }
 
+        bool  device_default::set_mode(device_mode mode) {
+            return true;
+        }
 
         /* ======================================================================= */
         /*  LOCKER                                                                 */

src/device/device_ledger.cpp

@@ -511,12 +511,13 @@ namespace hw {
         return true;
     }
 
-    bool  device_ledger::get_secret_keys(crypto::secret_key &viewkey , crypto::secret_key &spendkey) {
+    bool  device_ledger::get_secret_keys(crypto::secret_key &vkey , crypto::secret_key &skey) {
         AUTO_LOCK_CMD();
-      memset(viewkey.data, 0x00, 32);
-      memset(spendkey.data, 0xFF, 32);
 
-      #ifdef DEBUG_HWDEVICE
+        //secret key are represented as fake key on the wallet side
+        memset(vkey.data, 0x00, 32);
+        memset(skey.data, 0xFF, 32);
+
         //spcialkey, normal conf handled in decrypt
         int offset;
         reset_buffer();
@@ -535,11 +536,21 @@ namespace hw {
         this->length_send = offset;
         this->exchange();
 
-        //clear key
+        //View key is retrievied, if allowed, to speed up blockchain parsing
-        memmove(ledger::viewkey.data,  this->buffer_recv+64, 32);
+        memmove(this->viewkey.data,  this->buffer_recv+0,  32);
-        memmove(ledger::spendkey.data, this->buffer_recv+96, 32);
+        if (is_fake_view_key(this->viewkey)) {
+          MDEBUG("Have Not view key");
+          this->has_view_key = false;
+        } else {
+          MDEBUG("Have view key");
+          this->has_view_key = true;
+        }
       
+        #ifdef DEBUG_HWDEVICE
+        memmove(dbg_viewkey.data, this->buffer_recv+0, 32);
+        memmove(dbg_spendkey.data, this->buffer_recv+32, 32);
         #endif
+
         return true;
     }
 
@@ -585,8 +596,6 @@ namespace hw {
 
     bool device_ledger::derive_subaddress_public_key(const crypto::public_key &pub, const crypto::key_derivation &derivation, const std::size_t output_index, crypto::public_key &derived_pub){
         AUTO_LOCK_CMD();
-        int offset;
-
         #ifdef DEBUG_HWDEVICE
         const crypto::public_key pub_x = pub;
         crypto::key_derivation derivation_x;
@@ -643,7 +652,7 @@ namespace hw {
 
         //pub key
         memmove(derived_pub.data, &this->buffer_recv[0], 32);
-
+      }
       #ifdef DEBUG_HWDEVICE
       hw::ledger::check32("derive_subaddress_public_key", "derived_pub", derived_pub_x.data, derived_pub.data);
       #endif
@@ -1033,7 +1042,7 @@ namespace hw {
 
     bool device_ledger::generate_key_derivation(const crypto::public_key &pub, const crypto::secret_key &sec, crypto::key_derivation &derivation) {
         AUTO_LOCK_CMD();
-        int offset;
+        bool r = false;
 
         #ifdef DEBUG_HWDEVICE
         const crypto::public_key pub_x = pub;
@@ -1095,10 +1104,6 @@ namespace hw {
       return r;
     }
 
-
-      return true;
-    }
-
     bool device_ledger::derivation_to_scalar(const crypto::key_derivation &derivation, const size_t output_index, crypto::ec_scalar &res) {
         AUTO_LOCK_CMD();
         int offset;
@@ -1384,32 +1389,6 @@ namespace hw {
         return true;
     }
 
-    bool  device_ledger::set_signature_mode(unsigned int sig_mode) {
-        AUTO_LOCK_CMD();
-        int offset ;
-
-        reset_buffer();
-
-        this->buffer_send[0] = 0x00;
-        this->buffer_send[1] = INS_SET_SIGNATURE_MODE;
-        this->buffer_send[2] = 0x01;
-        this->buffer_send[3] = 0x00;
-        this->buffer_send[4] = 0x00;
-        offset = 5;
-        //options
-        this->buffer_send[offset] = 0x00;
-        offset += 1;
-        //account
-        this->buffer_send[offset] = sig_mode;
-        offset += 1;
-
-        this->buffer_send[4] = offset-5;
-        this->length_send = offset;
-        this->exchange();
-        
-      return true;
-    }
-
     bool device_ledger::encrypt_payment_id(crypto::hash8 &payment_id, const crypto::public_key &public_key, const crypto::secret_key &secret_key) {
         AUTO_LOCK_CMD();
         int offset;

src/device/device_ledger.hpp

@@ -138,6 +138,7 @@ namespace hw {
         bool connect(void) override;
         bool disconnect() override;
 
+        bool  set_mode(device_mode mode) override;
 
         /* ======================================================================= */
         /*  LOCKER                                                                 */