Update keygen to fix index alignment

examples/real_airtag.py

@@ -5,7 +5,8 @@ Example showing how to retrieve the primary key of your own AirTag, or any other
 This key can be used to retrieve the device's location for a single day.
 """
 import plistlib
-from datetime import datetime
+from datetime import datetime, timedelta, timezone
+from pathlib import Path
 
 from findmy import FindMyAccessory
 
@@ -13,11 +14,11 @@ from findmy import FindMyAccessory
 # For nearby devices, you can use `device_scanner.py` to find it.
 PUBLIC_KEY = ""
 # Path to a .plist dumped from the Find My app.
-PLIST_PATH = "airtag.plist"
+PLIST_PATH = Path("airtag.plist")
 
 # == The variables below are auto-filled from the plist!! ==
 
-with open(PLIST_PATH, "rb") as f:
+with PLIST_PATH.open("rb") as f:
     device_data = plistlib.load(f)
 
 # PRIVATE master key. 28 (?) bytes.
@@ -29,30 +30,34 @@ SKN = device_data["sharedSecret"]["key"]["data"]
 # "Secondary" shared secret. 32 bytes.
 SKS = device_data["secondarySharedSecret"]["key"]["data"]
 
-# Lookahead in time slots. Each time slot is 15 minutes.
-# Should be AT LEAST the time that has passed since you paired the accessory!
-delta = datetime.now() - device_data["pairingDate"]
-MAX_LOOKAHEAD = int(delta.total_seconds() / (15 * 60)) + 1
-
 
 def main() -> None:
-    airtag = FindMyAccessory(MASTER_KEY, SKN, SKS)
+    paired_at = device_data["pairingDate"].replace(tzinfo=timezone.utc)
+    airtag = FindMyAccessory(MASTER_KEY, SKN, SKS, paired_at)
+
+    now = datetime.now(tz=timezone.utc)
+    lookup_time = paired_at.replace(
+        minute=paired_at.minute // 15 * 15,
+        second=0,
+        microsecond=0
+    ) + timedelta(minutes=15)
+
+    while lookup_time < now:
+        keys = airtag.keys_at(lookup_time)
+        for key in keys:
+            if key.adv_key_b64 != PUBLIC_KEY:
+                continue
 
-    for i in range(MAX_LOOKAHEAD):
-        prim_key, sec_key = airtag.keys_at(i)
-        if PUBLIC_KEY in (prim_key.adv_key_b64, sec_key.adv_key_b64):
             print("KEY FOUND!!")
-            print(f"This key was found at index {i}."
-                  f" It was likely paired approximately {i * 15} minutes ago.")
-            print()
             print("KEEP THE BELOW KEY SECRET! IT CAN BE USED TO RETRIEVE THE DEVICE'S LOCATION!")
-            if prim_key.adv_key_b64 == PUBLIC_KEY:
-                print(f"PRIMARY key: {prim_key.private_key_b64}")
-            else:
-                print(f"SECONDARY key: {sec_key.private_key_b64}")
-            break
-    else:
-        print("No match found! :(")
+            print(f"  - Key:           {key.private_key_b64}")
+            print(f"  - Approx. Time:  {lookup_time}")
+            print(f"  - Type:          {key.key_type}")
+            return
+
+        lookup_time += timedelta(minutes=15)
+
+    print("No match found! :(")
 
 
 if __name__ == "__main__":