Re: AES CFB mode

Paul Rubin <[email protected]> Tue, 21 May 2002 00:55:53 -0000

Newsgroups	gmane.comp.python.cryptography
Message-ID	<[email protected]>

    Forgive my previous pedantic question: I just didn't realize how
    CFB worked.  I assume the slowdown is due to the fact that in
    8-bit CFB, an entire BLOCK_SIZE is encrypted for each byte of
    output. I am thinking of reducing BLOCK_SIZE for my purposes ( CFB
    only ). Any recommendations?

If you change the block size, it's not AES any more.  You can change
the feedback size--for example you can set it to be the same as
the block size, so you'll get one encryption per block, if your
application can work that way.  If it can, though, you probably
don't need CFB mode in the first place.