PGP stands for Pretty Good Privacy. It is an encryption program that is freely available. You can use it to encode messages for others or to read messages sent to you. It is unbreakable within practical limits.

PGP is based on public keys. That means you have a public key that you can freely pass around to anybody. Using your public key they can generate encrypted messages that only you can decode using your secret private key. You never give out your private key. Similarly you can generate messages for others using their public key, which only they can decode by using their secret private keys.

You can also create unique signatures using your private key that will authenticate messages you send for others. Only you with your private key can create such a signature, but anybody with your public key can check if it is valid.

PGP is available for DOS, Mac, and several other systems.

The latest version is 2.6. It is available from MIT.

Check out the PGP FAQ.

There is a book about PGP:

PGP: Pretty Good Privacy by Simson Garfinkel 1st Edition November 1994 (est.) 250 pages (est),ISBN: 1-56592-098-8, $17.95 (est)

Here are some locations of MacPGP 2.2 that I know about:

Host (IP:

Location: /micros/mac/umich/util/encryption

FILE -r--r--r-- 312726 Mar 14 02:45 macpgp2.2.cpt.hqx

Host (IP:

Location: /computing/systems/mac/umich/util/encryption

FILE -rw-rw-r-- 287112 Mar 14 02:45 macpgp2.2.cpt.hqx.Z

Host (IP:

Location: /mirrors3/

FILE -r--r--r-- 312726 Mar 13 20:45 macpgp2.2.cpt.hqx

Host (IP:

Location: /pub/cypherpunks/pgp

FILE -rw-r--r-- 312726 Mar 17 07:53 macpgp2.2.cpt.hqx

Host (IP:

Location: /pub/user-supported/cypherpunks

FILE -rw-r--r-- 312726 Mar 17 14:25 macpgp2.2.cpt.hqx