diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..bee8a64
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+__pycache__
diff --git a/Day 12/BackToBasic.exe b/Day 12/BackToBasic.exe
new file mode 100644
index 0000000..6dbe398
Binary files /dev/null and b/Day 12/BackToBasic.exe differ
diff --git a/Day 12/decode.py b/Day 12/decode.py
new file mode 100644
index 0000000..88aa947
--- /dev/null
+++ b/Day 12/decode.py	
@@ -0,0 +1,11 @@
+#!/usr/bin/python
+
+def xor(str1, str2):
+    l = min(len(str1), len(str2))
+    return "".join(chr(int(str1[i]) ^ int(str2[i])) for i in range(l))
+
+str3 = b"6klzic<=bPBtdvff'y\x7fFI~on//N" # expected input encrypted
+str1 = b"AAAAAAAAAAAAAAAAAAAAAAAAAAA"    # input
+str2 = b"GFIHKJMLONQPSRUTWVYX[Z]\_^a"    # input encrypted
+key = xor(str1, str2).encode("UTF-8")    # key
+print("HV19{%s}" % xor(str3, key))