This file is correct as of tin-1.5.8

Ensuring support is compiled in
-------------------------------
Tin will compile in support for PGP or GPG if it can find it.

It looks for 'pgp' on the path
If this is found, then PGP2 support is assumed
It looks for 'pgpk' on the path
If this is found, then PGP5 support is assumed
It looks for 'gpg' on the path
If this is found, then GPG support is assumed
If neither is found, then no pgp and gpg support is compiled in

If you have more than one of these programs installed, you have to decide
which of these should be used by tin. By default, PGP2 is preferred over PGP5
and PGP5 over GPG. If you want to use PGP2 or PGP5 and GPG is installed, make
sure that you invoke configure with --without-gpg (otherwise appending public
keys will fail). If you want to use GPG, invoke configure with --without-pgp
and --without-pgpk. To use PGP5, invoke configure with --without-pgp and
--without-gpg.

If configure is called with --disable-pgp-gpg, then no pgp and gpg support is
compiled in.

When you try to use PGP
-----------------------
PGP2 support expects pubring.pgp
PGP5 support expects pubring.pkr
GPG support expects pubring.gpg

It wants to find the above in:
$HOME/.pgp/pubring.* if using PGP2 or PGP5
$HOME/.gnupg/pubring.gpg if using GPG

Or you can override this with $PGPPATH/pubring.*

If an environment var PGPOPTS is defined, then tin will use it.

Internal usage of PGP
---------------------
There are 3 places where pgp is invoked:

1) Checking articles (^G in the pager)

   If the article is pgp signed (-----BEGIN PGP SIGNED MESSAGE-----)

   PGP2:  pgp -f $PGPOPTS <article >/dev/null
   PGP5:  pgpv -f $PGPOPTS <article >/dev/null
   GPG:   gpg $PGPOPTS --nobatch --decrypt <article >/dev/null

   If the article has (-----BEGIN PGP PUBLIC KEY BLOCK-----)

   pgp $PGPOPTS -ka article
   pgpk $PGPOPTS -a article
   gpg $PGPOPTS --nobatch --import article

2) When posting news or mail

   For signing when tinrc.mail_address or attributes.from is not defined:

   PGP2:  pgp $PGPOPTS -ats plaintextfile to_address
   PGP5:  pgps $PGPOPTS -at plaintextfile to_address
   GPG:   gpg $PGPOPTS --textmode --armor --no-batch --output
              plaintextfile.asc --escape-from --clearsign plaintextfile

   For signing and encrypting when tinrc.mail_address or attributes.from is
   not defined:

   PGP2:  pgp $PGPOPTS -ates plaintextfile to_address
   PGP5:  pgpe $PGPOPTS -ats plaintextfile to_address
   GPG:   gpg $PGPOPTS --textmode --armor --no-batch --output
              plaintextfile.asc --recipient to_address --sign --encrypt
              plaintextfile

   For signing when tinrc.mail_address or attributes.from is defined:

   PGP2:  pgp $PGPOPTS -ats plaintextfile to_address -u from_address
   PGP5:  pgps $PGPOPTS -at plaintextfile to_address -u from_address
   GPG:   gpg $PGPOPTS --textmode --armor --no-batch --local-user
              from_address --output plaintextfile.asc --escape-from
              --clearsign plaintextfile

   For signing and encrypting when tinrc.mail_address or attributes.from is
   defined:

   PGP2:  pgp $PGPOPTS -ates plaintextfile to_address -u from_address
   PGP5:  pgpe $PGPOPTS -ats plaintextfile to_address -u from_address
   GPG:   gpg $PGPOPTS --textmode --armor --no-batch --output
              plaintextfile.asc --recipient to_address --local-user
              from_address --sign --encrypt plaintextfile

   For encrypting:

   PGP2:  pgp $PGPOPTS -ate plaintextfile to_address
   PGP5:  pgpe $PGPOPTS -at plaintextfile to_address
   GPG:   gpg $PGPOPTS --textmode --armor --no-batch --output
              plaintextfile.asc --recipient to_address --encrypt
              plaintextfile

3) Appending public key

   PGP2: pgp $PGPOPTS -kxa from_address keyfile
   PGP5: pgpk $PGPOPTS -xa from_address -o keyfile
   GPG:  gpg $PGPOPTS --nobatch --armor --output keyfile --export
             from_address

   Where from_address is the posting/mailing address
