Symmetric encryption

David Shaw dshaw at
Sun Jul 28 22:23:02 CEST 2002

On Sun, Jul 28, 2002 at 12:24:21PM -0400, Gordon Worley wrote:
> On Sunday, July 28, 2002, at 12:08  PM, David Shaw wrote:
> >I'm not exactly sure what you are asking.  As you say, you can use
> >--cipher-algo to set the cipher to use.  If you don't specify
> >something, it uses whatever the s2k-cipher-algo is.
> I'm looking at this from a GPGME perspective.  If I tell GnuPG to 
> symmetrically encrypt a file, I'd like for GnuPG to tell me what 
> algorithm was used so that I can tell the user (in case they let it 
> default to the s2k cipher algorithm, which the average user probably 
> doesn't know off hand).  Maybe there's no way to do it?

In the case of the "new style" symmetric messages (where a session key
is used), the header shows the cipher, so the user will be properly
prompted.  In the old style PGP2 symmetric messages, there is no way
to know the cipher without telling the user somehow - the message
doesn't contain it.

> >The s2k cipher
> >algo defaults to CAST5.
> A quick test will show that you are correct, but the documentation says 
> that the default is Blowfish.

Yes.  This is fixed (the documentation, that is) in 1.1.90.


   David Shaw  |  dshaw at  |  WWW
   "There are two major products that come out of Berkeley: LSD and UNIX.
      We don't believe this to be a coincidence." - Jeremy S. Anderson

More information about the Gnupg-devel mailing list