def aead_filename(aead_dir, key_handle, public_id):
parts = [aead_dir, key_handle] + pyhsm.util.group(public_id, <NUM_LIT:2>)<EOL>path = os.path.join(*parts)<EOL>if not os.path.isdir(path):<EOL><INDENT>os.makedirs(path)<EOL><DEDENT>return os.path.join(path, public_id)<EOL>
Return the filename of the AEAD for this public_id,
and create any missing directorys.