SFT-3834: ensured preview address matches the signed output address

diff --git a/ports/stm32/boards/Passport/modules/flows/health_check_common_flow.py b/ports/stm32/boards/Passport/modules/flows/health_check_common_flow.py
index 45a0562..4981dc9 100644
--- a/ports/stm32/boards/Passport/modules/flows/health_check_common_flow.py
+++ b/ports/stm32/boards/Passport/modules/flows/health_check_common_flow.py
@@ -61,7 +61,7 @@ class HealthCheckCommonFlow(Flow):
             node = sv.derive_path(self.subpath)
             self.address = sv.chain.address(node, self.addr_type)
 
-        self.address = stylize_address(self.address)
+        display_address = stylize_address(self.address)
 
         result = await LongTextPage(centered=True,
                                     text=('\n' + self.text),
@@ -71,7 +71,7 @@ class HealthCheckCommonFlow(Flow):
             self.set_result(False)
             return
 
-        result = await LongQuestionPage(text='Sign message with this address?\n\n{}'.format(self.address),
+        result = await LongQuestionPage(text='Sign message with this address?\n\n{}'.format(display_address),
                                         right_micron=microns.Sign,
                                         margins=MARGIN_FOR_ADDRESSES,
                                         top_margin=8).show()
@@ -88,7 +88,7 @@ class HealthCheckCommonFlow(Flow):
         from utils import spinner_task
         text = 'Signing message' if self.normal_signing else 'Performing health check'
         (signature, address, error) = await spinner_task(text, sign_text_file_task,
-                                                         args=[self.text, self.subpath, self.addr_type])
+                                                         args=[self.text, self.subpath, self.addr_type, self.address if self.normal_signing else None])
         if error is None:
             self.signature = signature
             self.address = address
diff --git a/ports/stm32/boards/Passport/modules/flows/health_check_qr_flow.py b/ports/stm32/boards/Passport/modules/flows/health_check_qr_flow.py
index 758e223..3f6ea41 100644
--- a/ports/stm32/boards/Passport/modules/flows/health_check_qr_flow.py
+++ b/ports/stm32/boards/Passport/modules/flows/health_check_qr_flow.py
@@ -4,11 +4,6 @@
 # health_check_flow.py - Scan and process a health check QR code in `crypto-request` format
 
 from flows import Flow
-from pages import ErrorPage, SuccessPage
-from pages.show_qr_page import ShowQRPage
-from utils import validate_sign_text, spinner_task
-from tasks import sign_text_file_task
-from public_constants import AF_CLASSIC, RFC_SIGNATURE_TEMPLATE
 from data_codecs.qr_type import QRType
 from foundation import ur
 
@@ -18,8 +13,8 @@ class HealthCheckQRFlow(Flow):
         super().__init__(initial_state=self.scan_qr, name='HealthCheckQRFlow')
 
         self.service_name = context
-        self.text = None
-        self.subpath = None
+        self.lines = None
+        self.signed_message = None
 
     async def scan_qr(self):
         from pages import ErrorPage
@@ -35,55 +30,29 @@ class HealthCheckQRFlow(Flow):
 
         try:
             data = result.unwrap_bytes().decode('utf-8')
-            lines = data.split('\n')
-            if len(lines) != 2:
-                await ErrorPage('Health check format is invalid.').show()
-                self.set_result(False)
-                return
-
-            self.text = lines[0]
-            self.subpath = lines[1]
+            self.lines = data.split('\n')
         except Exception as e:
             await ErrorPage('Health check format is invalid.').show()
             self.set_result(False)
             return
 
-        # Validate
-        (subpath, error) = validate_sign_text(self.text, self.subpath)
-        if error is not None:
-            await ErrorPage(text=error).show()
-            self.set_result(False)
-            return
+        self.goto(self.common_flow)
 
-        self.subpath = subpath
-        self.goto(self.sign_health_check)
+    async def common_flow(self):
+        from flows import HealthCheckCommonFlow
 
-    async def sign_health_check(self):
-        (signature, address, error) = await spinner_task('Performing Health Check',
-                                                         sign_text_file_task,
-                                                         args=[self.text, self.subpath, AF_CLASSIC])
-        if error is None:
-            self.signature = signature
-            self.address = address
-            self.goto(self.show_signed_message, save_curr=False)
-        else:
-            await ErrorPage(text='Error while signing file: {}'.format(error)).show()
+        self.signed_message = await HealthCheckCommonFlow(self.lines).run()
+        if self.signed_message is None:
             self.set_result(False)
             return
+        self.goto(self.show_signed_message)
 
     async def show_signed_message(self):
-        from ubinascii import b2a_base64
-
-        sig = b2a_base64(self.signature).decode('ascii').strip()
-
-        signed_message = ur.new_bytes(RFC_SIGNATURE_TEMPLATE.format(addr=self.address,
-                                                                    msg=self.text,
-                                                                    blockchain='BITCOIN',
-                                                                    sig=sig))
+        from pages import ShowQRPage
 
         result = await ShowQRPage(
             qr_type=QRType.UR2,
-            qr_data=signed_message,
+            qr_data=ur.new_bytes(self.signed_message),
             caption='Signed Health Check'
         ).show()
         if not result:
diff --git a/ports/stm32/boards/Passport/modules/tasks/sign_text_file_task.py b/ports/stm32/boards/Passport/modules/tasks/sign_text_file_task.py
index d167a54..89dd303 100644
--- a/ports/stm32/boards/Passport/modules/tasks/sign_text_file_task.py
+++ b/ports/stm32/boards/Passport/modules/tasks/sign_text_file_task.py
@@ -14,12 +14,16 @@ import chains
 from utils import sign_message_digest_recoverable
 
 
-async def sign_text_file_task(on_done, text, subpath, addr_fmt):
+async def sign_text_file_task(on_done, text, subpath, addr_fmt, expected_address=None):
 
     with stash.SensitiveValues() as sv:
         node = sv.derive_path(subpath)
         address = sv.chain.address(node, addr_fmt)
 
+    if expected_address is not None and address != expected_address:
+        await on_done(None, None, 'Address mismatch: expected {}, got {}'.format(expected_address, address))
+        return
+
     digest = chains.current_chain().hash_message(text.encode())
     # signature will be 65 bytes
     signature = sign_message_digest_recoverable(digest, subpath)