gnutar + pgp filter mode

-----BEGIN PGP SIGNED MESSAGE-----

The gnu tar archiver allows to use an arbitrary
compression program (option --use-compress-program=PROG).

This works well with pgp if a small wrapper is used:

#!/bin/csh -fb

if ("$1" == "-d") then
  exec pgp -d -f
else
  exec pgp -e -f
endif




The only problem is that this doesn't work well for
larger amounts of data, because pgp reads in all
data before starting with its work.


Perhaps a future release of pgp will have a real filter
mode.


Hadmut

BTW: Does this "crypto-hook" cause export restrictions to 
apply on gtar ?


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> The only problem is that this doesn't work well for
> larger amounts of data, because pgp reads in all
> data before starting with its work.
> 
> Perhaps a future release of pgp will have a real filter
> mode.

The problem is not with PGP but with the PGP message formatsa.  With
the current message formats you need to know the size of data before
you can output the header that precedes it.  As a result, whole
messages must somehow be buffered before PGP can output them.

The fix is to create new, one-pass packets, which will allow PGP to
generate messages in a single pass.  These new packet formats are
still in the design stage and will probably not be supported in PGP
3.0.

-derek