feat(core): use random suffix for BLE name when pairing

[no changelog]

core/src/apps/management/ble/pair_new_device.py

@@ -2,6 +2,7 @@ import trezorble as ble
 import trezorui_api
 from storage import device as storage_device
 from trezor import utils
+from trezor.crypto import random
 from trezor.ui.layouts import CONFIRMED, raise_if_not_confirmed
 from trezor.wire import ActionCancelled
 
@@ -13,8 +14,25 @@ def _end_pairing() -> None:
         ble.stop_advertising()
 
 
+def _default_ble_name() -> str:
+    """Return model name and three random letters.
+
+    >>> n1 = _default_ble_name()
+    >>> n1.startswith(utils.MODE_FULL_NAME)
+    True
+    >>> n2 = _default_ble_name()
+    >>> n2.startswith(utils.MODE_FULL_NAME)
+    True
+    >>> n1 == n2
+    False
+    """
+    charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
+    random_chars = "".join(charset[random.uniform(len(charset))] for _ in range(3))
+    return f"{utils.MODEL_FULL_NAME} ({random_chars})"
+
+
 async def pair_new_device() -> None:
-    label = storage_device.get_label() or utils.MODEL_FULL_NAME
+    label = storage_device.get_label() or _default_ble_name()
     ble.start_advertising(False, label)
     try:
         code = await raise_if_not_confirmed(