>>>> Buffer Encryption
>>>> ==============
>>>> We will use AES-CBC for buffer encryption. We will add key id (4byte)
>>>
>>> I think we might want to use CTR for this, and will post after this.
>
> Not sure if I missed this post or not (as several people mentioned, it
> is easy to get lost in this thread).
>
> I think what will help drive this decision is whether or not we consider
> the data we are storing on disk as a "file system" in itself. Trying to
> make myself literate in disk encryption theory[1], it seems a big
> weakness in using CTR mode for encryption is we need to be able to
> guarantee a fresh counter for every page we encrypt[2], so if we can
> guarantee the uniqueness of IV per TDEK, this is on the table.
>
> XTS mode, on the other hand, appears to be more durable to reusing an IV
> as the "tweak" was designed to represent a disk sector, though there are
> still problems. However, I presume this is one of many reasons why
> fscrypt uses XTS[3].
Much like Joe earlier, I forgot my citations:
[1] https://en.wikipedia.org/wiki/Disk_encryption_theory
[2]
https://crypto.stackexchange.com/questions/14628/why-do-we-use-xts-over-ctr-for-disk-encryption
[3] https://www.kernel.org/doc/html/latest/filesystems/fscrypt.html
Jonathan
