PGP: Pretty Good Privacy
Secure Message Encryption

It's not within the scope of this documentation to teach you PGP. Here are a few links that may get you started, if necessary:

online: www.wikipedia.org/pretty_good_privacy
online: www.google.com/PGP_tutorial
online: www.google.com/GPG_tutorial

That having been said, you don't need prior knowledge to use PGP conventional encryption.

Using PGP

There are 2 types of PGP encryption--symmetric encryption, also know as conventional encryption, and asymmetric or public key encryption. The former requires only a password to encrypt the text, while the latter requires those corresponding create and exchange special cryptographic keys.

PGP Conventional Encryption

QS needs no setup to use PGP conventional encryption. Just choose a password. You'll need to inform the message recipient of the password--in a secure manner as well. That can be as simple as telling him/her face to face. The easiest way to use conventional encryption in QS is by simply depressing the PGP Encrypt button on the editor toolbar. If you're creating a template, the status of this button will be saved with the template. A second method to add conventional encryption is to add this header to your message:

Pgp: encrypt

The Pgp header can be anywhere among the headers of your message. First is good. Either by button or header, when you click the Send button, you'll be presented with a PGP Passphrase Dialog and your message will be encrypted before leaving the editor.

Also, see PGP Decryption below.



PGP Public Key Encryption

This is the more technical endeavor. For this type of encryption, you need a set of PGP public and private keyrings. Any version of PGP or GPG can get you started. You'll also need to exchange public PGP keys with the individuals you'll be writing. PGP Public Key Encryption must be enabled on the PGP tab of the QS Options Dialog.

The simplest method to use PGP public key encryption and signing is to depress the PGP Encrypt button and/or PGP Sign button on the Editor toolbar. Signing is the act of digitally marking your email such that it is guaranteed to be from you and not an impostor. The same marking verifies that the text is exactly as you wrote it and not modified in transit. When creating templates the status of the Encrypt and Sign buttons are saved with the template. When the Send button is clicked, if the Encrypt button is depressed, the PGP Encrypt To Recipients Dialog will appear. Select recipients or Click the Conventional Encryption box if that's desired instead. If the Sign button is depressed, the Secret Key Passphrase Dialog will appear with the default key selected. Select a different key if necessary and enter the passphrase to continue.

The various scenarios can be carried out using one these Pgp headers:

Pgp: encrypt; sign;
Pgp: encrypt
Pgp: sign

If you're creating a template, there's a more efficient means of specifying the desired operations. Suppose you're creating a template to a specific recipient. Using the Pgp header instead of the PGP toolbar buttons, you can specify recipient keys like this:

Pgp: encrypt=0x946A90C3
Pgp: encrypt=0x0CC6E051,0x0D6E1725,0x97E7FD09,...

Using this method, the PGP Encrypt To Recipients Dialog won't appear. The message will be encrypted to the key ID's you've given.

Signing can be handled in the same manner. Create a Pgp header like this:

Pgp: sign=0x67D0D303

In this case, only one key ID can be used. You can only sign with one key. This will be your secret key. But, you may have more than one. By specifying the key ID, that key will be automatically selected in the Secret Key Passphrase Dialog when it opens.

Of course, both encrypting and signing can be carried out in the same header like this:

Pgp: encrypt=0x0CC6E051,0x97E7FD09; sign=0x67D0D303;

One Further Encryption Possibility

A QS message can contain more than one Pgp header. They are processed from the top down. Here's a far fetched example for it's use. You want to send an encrypted message to friend A, who will deliver the message to friend B, but friend A cannot know the contents of the message. The two headers below, both in the same message, show how this can be accomplished. When Send is clicked, the message is encrypted to friend B's key (0x0CC6E051). Then that encrypted text is encrypted again. This time to friend A's key (0x67D0D303). When friend A gets the message, he decrypts it and finds the encrypted message for friend B. Essentially, that's how the remailer network works! The actual message to friend B might be encrypted in three, four or more layers, depending on the length of the remailer chain. With mixmaster messages, all layers of encryption are applied before the message leaves your computer.

Pgp: encrypt=0x0CC6E051
Pgp: encrypt=0x67D0D303

It should be noted, this is a special purpose feature and is not part of normal usage.

PGP Decryption

If you receive an encrypted message via another email program, QS will decrypt the message for you. When importing the message into QS using Clipboard/Reply..., QS will see the message is encrypted and ask for the passphrase. To use Clipboard/Reply you must first copy the message from the other email program, to the clipboard--including the message headers.