diff --git a/day25.py b/day25.py
new file mode 100644
index 0000000..58a9896
--- /dev/null
+++ b/day25.py
@@ -0,0 +1,36 @@
+import aoclib
+
+DAY = 25
+TEST_SOLUTION_PART1 = 14897079
+TEST_SOLUTION_PART2 = 0
+
+
+def transform(key, subject_number, loop_size=1):
+    for _ in range(loop_size):
+        key = key * subject_number % 20201227
+
+    return key
+
+def part1(test_mode=False):
+    my_input = aoclib.getInputAsArray(day=DAY, return_type=int, test=test_mode)
+
+    loop_card = 0
+    public_key_card = 1
+    while public_key_card != my_input[0]:
+        loop_card += 1
+        public_key_card = transform(public_key_card, 7)
+
+    loop_door = 0
+    public_key_door = 1
+    while public_key_door != my_input[1]:
+        loop_door += 1
+        public_key_door = transform(public_key_door, 7)
+
+    print("Loops: %d (card), %d (door)" % (loop_card, loop_door))
+
+    return transform(1, public_key_door, loop_card)
+
+
+def part2(test_mode=False):
+    # there is no part2 for day 25
+    return 0
diff --git a/inputs/25 b/inputs/25
new file mode 100644
index 0000000..8e139ed
--- /dev/null
+++ b/inputs/25
@@ -0,0 +1,2 @@
+8335663
+8614349
diff --git a/inputs/25_test b/inputs/25_test
new file mode 100644
index 0000000..9cbfc23
--- /dev/null
+++ b/inputs/25_test
@@ -0,0 +1,2 @@
+5764801
+17807724