D&A Software - Post/LX and PGP

POST/LX and PGP

Here is how I configured PGP and POST/LX on my palmtop so that they work together. You will have to adapt some items, but generally, it should work for you too.

If you are not yet familiar with PGP or don't have a version running on the palmtop yet, you may want to look at http://www.cryptography.org/getpgp.htm or http://www.cryptography.org/getpgp.txt. Also, check out a GUI for PGP at http://sac.uky.edu/~wally/lxpgp.zip.

The main problem with making PGP and POST/LX work together is the memory limitations of DOS. The key to solve those problems is MaxDOS.

This text assumes you already have the PGP software by Philip Zimmerman and have installed it. It also assumes you have installed MaxDOS. Last but not least, this text assumes you are using PE (PalEdit) as your text editor for POST/LX.

What needs to be done

Either terminate System manager or run everything in a separate SC (Software Carousel) session. There is not enough memory space to make POST/LX and PGP work together within System Manager.

Before starting POST/LX (and WWW/LX), make sure MaxDOS is running (e.g. by installing it in AUTOEXEC.BAT using

 MAXDOS -l

Also make sure, in CONFIG.TXT (the configuration file for PGP), you have set up

 CharSet = Latin1
 Pager = pe          (or whatever your editor is)
 Verbose = 0         (unless you want PGP to be chatty)

Now create four batch files and make sure they are on the DOS path. The first batch file adds an ASCII signature to a text. It is named PGPSIGN.BAT:

 @echo off
 SET PGPPATH=c:\pgp
 c:\pgp\PGP.EXE -sta %1 -o scratch.

This assumes PGP.EXE is in C:\PGP. Adjust the paths to whatever is appropriate.

The second batch file encodes a complete message. It is named PGPENC.BAT:

 @echo off
 SET PGPPATH=c:\pgp
 c:\pgp\PGP.EXE -esa %1 -o scratch.

Again, adjust the paths. The third batch file is used to decode an encoded message. It is named PGPDEC.BAT:

 @echo off
 SET PGPPATH=c:\pgp
 c:\pgp\PGP.EXE -m %1

Note that it uses the -m option, which tells PGP to open a decoded file in PE (or whatever you have set up as "Pager" in CONFIG.TXT) so that you can read it and save it if you want.

The last batch file, named PGPVERY.BAT verifies a signature:

 @echo off
 SET PGPPATH=c:\pgp
 c:\pgp\PGP.EXE %1

Now we need to link all together. In PE.CFG, add the following lines to the [Filter] section:

 PGP &Sign = maxdos d:\dos\command.com /c PGPSIGN.BAT %s
 PGP &Encode = maxdos d:\dos\command.com /c PGPENC.BAT %s

And in POST.CFG, you need to add to the [External] section:

 PGP &Verify=maxdos d:\dos\command.com /c pgpvery.bat $f $$
 &PGP Decode=maxdos d:\dos\command.com /c pgpdec.bat $f

That's it.

How To Use It

Make sure that MaxDOS is loaded, then start WWW/LX and POST/LX with either System Manager terminated or in a separate SC session with as much memory available as possible.

Adding a PGP Signature to a Message

When you have finished composing a message in PE, select the complete message text in PE and then press Ctrl-XR to get the filter menu and then S to sign the message (or choose "PGP Sign" from the menu. PGP will ask you for your passphrase and then compute the signature. You will end up back in PE and the signature should be appended to the message.

Encoding a Message

When you have finished composing a message in PE, select the complete message text in PE and then press Ctrl-XR to get the filter menu and then E to sign the message (or choose "PGP Encode" from the menu. PGP will ask you for your passphrase and the name of the receipient and then compute the encoded message. You will end up back in PE and the message will be replaced by the encoded version.

Verifying a Signature

When reading a message in the message view of POST/LX you may see that it has a PGP signature. To verify that signature, press Ctrl-X and then V (or choose "PGP Verify" from the menu). PGP will be started and let you know if the signature is valid. Press a key to return to POST/LX.

Decoding a Message

When trying to read a message in the message view of POST/LX, you may see that it is encoded. Press Ctrl-X and then P (or choose "PGP Decode" from the menu). PGP will be started and it will ask you for your passphrase. Then it will decode the message and present it within PE. There you can read the message, save it, or do with it whatever you want. Quit PE to return to POST/LX.

Prepared by Andreas Garzotto