Day 12 solved

.gitignore

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+__pycache__

Day 12/decode.py

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+#!/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))