diff --git a/MobileAuthApp/app/src/main/java/com/tarkvaraprojekt/mobileauthapp/auth/AuthAppException.kt b/MobileAuthApp/app/src/main/java/com/tarkvaraprojekt/mobileauthapp/auth/AuthAppException.kt
new file mode 100644
index 0000000..96b05d5
--- /dev/null
+++ b/MobileAuthApp/app/src/main/java/com/tarkvaraprojekt/mobileauthapp/auth/AuthAppException.kt
@@ -0,0 +1,10 @@
+package com.tarkvaraprojekt.mobileauthapp.auth
+
+/**
+ * A specialised RuntimeException class for exceptions related to the mobile authentication app.
+ * Possible error codes can be found at
+ * https://github.com/TanelOrumaa/Estonian-ID-card-mobile-authenticator-POC/wiki/Error-codes
+ * @param message Error message
+ * @param code An error code defined in the project wiki
+ */
+open class AuthAppException(message: String, var code: Int) : RuntimeException(message)
\ No newline at end of file
diff --git a/MobileAuthApp/app/src/main/java/com/tarkvaraprojekt/mobileauthapp/auth/InvalidCANException.kt b/MobileAuthApp/app/src/main/java/com/tarkvaraprojekt/mobileauthapp/auth/InvalidCANException.kt
new file mode 100644
index 0000000..073c790
--- /dev/null
+++ b/MobileAuthApp/app/src/main/java/com/tarkvaraprojekt/mobileauthapp/auth/InvalidCANException.kt
@@ -0,0 +1,7 @@
+package com.tarkvaraprojekt.mobileauthapp.auth
+
+/**
+ * An AuthAppException for when the user entered CAN does not match the one read from the ID-card
+ * @see AuthAppException
+ */
+class InvalidCANException : AuthAppException("Invalid CAN", 400)
\ No newline at end of file
diff --git a/MobileAuthApp/app/src/main/res/values-en/strings.xml b/MobileAuthApp/app/src/main/res/values-en/strings.xml
index 36dce82..69af501 100644
--- a/MobileAuthApp/app/src/main/res/values-en/strings.xml
+++ b/MobileAuthApp/app/src/main/res/values-en/strings.xml
@@ -44,7 +44,9 @@
     <string name="auth_instruction_text">Put the ID card against the phone to establish connection</string>
     <string name="time_left">Time left %d sek</string>
     <string name="no_time">No time left</string>
-    <string name="no_success">Wrong CAN</string>
+    <string name="err_unknown">Unknown error</string>
+    <string name="invalid_can">Wrong CAN</string>
+    <string name="tag_lost">Connection between device and ID-card lost</string>
 
     <!-- string resources for UserFragment layout -->
     <string name="user_name_label">NAME</string>
@@ -75,4 +77,7 @@
     <string name="hidden_pin">****</string>
     <string name="unavailable">Settings currently unavailabe</string>
     <string name="can_save_request">CAN is currently not saved. Do you wish to save the CAN? Saved CAN will be entered automatically in the future. Saved CAN can be changed and deleted in the settings menu.</string>
+    <string name="err_reading_card">Failed to read data from the ID-card</string>
+    <string name="err_internal">Internal error</string>
+    <string name="err_bad_data">Read bad data from the ID-card, try using the card again</string>
 </resources>
\ No newline at end of file
diff --git a/MobileAuthApp/app/src/main/res/values-et/strings.xml b/MobileAuthApp/app/src/main/res/values-et/strings.xml
index 63c0eae..1dedbd0 100644
--- a/MobileAuthApp/app/src/main/res/values-et/strings.xml
+++ b/MobileAuthApp/app/src/main/res/values-et/strings.xml
@@ -43,7 +43,9 @@
     <string name="auth_instruction_text">ID kaardiga ühenduse loomiseks pane kaart vastu telefoni</string>
     <string name="time_left">Aega on jäänud %d sek</string>
     <string name="no_time">Aeg on otsas</string>
-    <string name="no_success">Vale CAN</string>
+    <string name="err_unknown">Tundmatu viga</string>
+    <string name="invalid_can">Vale CAN</string>
+    <string name="tag_lost">Ühendus seadme ja kaardi vahel katkes</string>
 
     <!-- string resources for UserFragment layout -->
     <string name="user_name_label">NIMI</string>
@@ -73,4 +75,7 @@
     <string name="hide">PEIDA</string>
     <string name="hidden_pin">****</string>
     <string name="unavailable">Seaded pole hetkel saadaval</string>
+    <string name="err_reading_card">Ei saanud ID-kaardilt andmeid lugeda</string>
+    <string name="err_internal">Rakendusesisene viga</string>
+    <string name="err_bad_data">ID-kaardilt loeti vigased andmed, proovi uuesti kaarti kasutada</string>
 </resources>
\ No newline at end of file
diff --git a/MobileAuthApp/app/src/main/res/values/strings.xml b/MobileAuthApp/app/src/main/res/values/strings.xml
index 9c2d2a7..ac0d78b 100644
--- a/MobileAuthApp/app/src/main/res/values/strings.xml
+++ b/MobileAuthApp/app/src/main/res/values/strings.xml
@@ -43,7 +43,9 @@
     <string name="auth_instruction_text">Put the ID card against the phone to establish connection</string>
     <string name="time_left">Time left %d sek</string>
     <string name="no_time">No time left</string>
-    <string name="no_success">Wrong CAN</string>
+    <string name="err_unknown">Unknown error</string>
+    <string name="invalid_can">Wrong CAN</string>
+    <string name="tag_lost">Connection between device and ID-card lost</string>
 
     <!-- string resources for UserFragment layout -->
     <string name="user_name_label">NAME</string>
@@ -73,4 +75,7 @@
     <string name="hide">HIDE</string>
     <string name="hidden_pin">****</string>
     <string name="unavailable">Settings currently unavailable</string>
+    <string name="err_reading_card">Failed to read data from the ID-card</string>
+    <string name="err_internal">Internal error</string>
+    <string name="err_bad_data">Read bad data from the ID-card, try using the card again</string>
 </resources>
\ No newline at end of file