Vim has a security issue with the blowfish encryption method because it reuses the first block's
IV in subsequent blocks. This makes possible to retrieve the keystream and decrypt the file as long
as the first 8 bytes of the file are known.
To use this script we need the encrypted file and another file with at least the first 8 plain-text bytes. Then we can run:
./break_vimbf1.py encrypted_file file_with_first_eight_bytes