Can you clarify when data compression is used?

David Shaw dshaw at
Mon Feb 4 15:44:18 CET 2008

On Mon, Feb 04, 2008 at 01:17:48AM -0600, Kevin Hilton wrote:
> On Feb 4, 2008 1:17 AM, Kevin Hilton <kevhilton at> wrote:
> > Although  not supported on all systems (and not included on ubuntu by
> > default if you can believe it), does bzip2 offers the highest compression?

It depends on what you are compressing.  BZip2 tends to do better than
zip against straight text, for example.

> > I know that --personal-compress-preferences may be included in the
> > gpg.conf file to take advantage of bzip2 or zlib if desired.  Does PGP
> > still only recognize ZIP or no compression?

Current PGP handles BZip2, ZLIB, and Zip (and of course no

Even if you're communicating with a person whose program doesn't
support BZip2, it is safe to put BZip2 in your
personal-compress-preferences.  Those preferences are only used if all
parties agree, so you won't accidentally create an interoperability
problem.  This is true of all the personal-(whatever)-preferences


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