Some forms of encryption allow for keys that create evidence that has never existed before. A simple case is an XOR between random data and some illegal file (

Some forms of encryption allow for keys that create evidence that has never existed before. A simple case is an XOR between random data and some illegal file (that only hypothetically exists). That XOR is a key to creating the illegal file which never existed before. You cannot draw an analogy to any real world item locked up in some way, because in those cases a key could only ever reveal an item that already exists.