Re: different instructions for use with aes256?

[Bradley Worley <geekysuavo@xxxxxxxxx>]

thanks for clarifying, david.  i myself was wondering if that was the
case, but i guess i forgot what those other commands were actually
doing... [hits head on table]

 ~ brad.

On 10/25/05, David <shadoweyez@xxxxxxxxx> wrote:
> FYI the command
>
> head -c 2925 /dev/random | uuencode -m - | head -n 66 | tail -n 65 \
> | gpg --symmetric -a >/a/usbstick/keyfile.gpg
>
> produces a key that will work with AES128, 192, 256 or other cipher you
> use it with; it is independent of the cipher.  Because of the "head" and
> "tail" commands being used, you could type head -c 10000000 ... and
> still end up with a key of the same size.  I tried this once and any
> value equal to or over 2925 will not change the size of the key, because
> head and tail concatenate the output.
>
> When I setup loop-aes I used a patched version of gpg (the patch that
> came with loop-aes) as well as the --cipher-algo=AES256 option on gpg as
> gpg defaults to CAST5 as the cipher.
>
> David
>
>
> Marvin Lyndon wrote:
> > Well, I decided to just go ahead and use AES128. Concluded that, as with
> > all computing stuff, it is too easy to get carried away by the "let's go
> > for the largest number" mentality whenever confronted with a choice and
> > don't really know any of the details. : )
> >
> > With that out of the way, and just out of curiosity, could anyone clear
> > up the decision of having 2925 bytes? I can tell that divided by 65 it
> > means that each key will be 45 bytes long; but what is the rationale
> > here? My understanding of these issues is very dim, but how does this
> > number of 45 bytes relate with the use of AES128? Similarly, why would
> > someone using AES256 pick 90-byte keys?
> >
> > Thanks for educating me,
> >
> > Marv
> >
> >
> >> From: Bradley Worley <geekysuavo@xxxxxxxxx>
> >> To: Marvin Lyndon <marvin.lyndon@xxxxxxxxxxx>
> >> CC: linux-crypto@xxxxxxxxxxxx
> >> Subject: Re: different instructions for use with aes256?
> >> Date: Tue, 25 Oct 2005 15:37:49 -0500
> >>
> >> that code seems to work just fine, since almost all examples on the
> >> net use either 2925 bytes from /dev/random or 2880 bytes.  however, i
> >> guess if you really want to be picky you can up it to 5850 bytes
> >> (double 2925), since you are technically doubling your key sizes.
> >> (it's a wild guess, really.)
> >>
> >>   ~ brad.
> >>
> >> On 10/25/05, Marvin Lyndon <marvin.lyndon@xxxxxxxxxxx> wrote:
> >> > Hi all,
> >> >
> >> > I have successfully followed all the steps in the loop-AES readme file.
> >> > Since I couldn't find any reference to this, I would like to know
> >> whether
> >> > the step in which one creates the 65 random keys
> >> >
> >> > head -c 2925 /dev/random | uuencode -m - | head -n 66 | tail -n 65 \
> >> > | gpg --symmetric -a >/a/usbstick/keyfile.gpg
> >> >
> >> > needs any modification for use in AES256 mode. Or is it enough to
> >> replace
> >> > all occurrences of AES128 with AES256 as one follows the README file?
> >> >
> >> > Thanks for any help
> >> >
> >> > Marv
> >> >
> >> > _________________________________________________________________
> >> > FREE pop-up blocking with the new MSN Toolbar – get it now!
> >> > http://toolbar.msn.click-url.com/go/onm00200415ave/direct/01/
> >> >
> >> >
> >> > -
> >> > Linux-crypto:  cryptography in and on the Linux system
> >> > Archive:       http://mail.nl.linux.org/linux-crypto/
> >> >
> >> >
> >
> >
> > _________________________________________________________________
> > Don't just search. Find. Check out the new MSN Search!
> > http://search.msn.click-url.com/go/onm00200636ave/direct/01/
> >
> >
> > -
> > Linux-crypto:  cryptography in and on the Linux system
> > Archive:       http://mail.nl.linux.org/linux-crypto/
> >
> >
>
> -
> Linux-crypto:  cryptography in and on the Linux system
> Archive:       http://mail.nl.linux.org/linux-crypto/
>
>
Š{±r¼©¶‡+Ê›h‚¶©‡(§jwhžØ^.)îÆ̬µé€­Èb½èm¶Ÿÿ™¨¥žYbžìh®åŠ{±r¼©¶?