Comment 4 for bug 782646

The list of those "certain files" is not hard coded into ureadahead but is gathered by checking which files are accessed when booting and then saving that file list onto the hard drive. So if the encrypted partition is mounted early enough, ureadahead saves a list of files on that partition elsewhere, unencrypted.

I'm not that much into crypto analysis, so I can't tell how important this little known plain-text is in cracking the encryption. But I can imagine lots of encryption applications where even the exposure of the names of the encrypted files is a severe security breach.