Sorry for being a little nebulus. Public Key Encryption is also known as DES. (Data Encryption Standard.) It is just a way of making SURE that the only person who reads what you wrote, is the person you WANT to read it. I have an area on my hard drive called a PGP Disk. It is where I keep all my email files, and Word documents that could get me DF'ed. With the touch of one key, it is encrypted with a 4096 bit AES-256 military grade encryption code. And the passphrase is a long one, that resides ONLY in my head.
Op-Sec stands for Operational Security. It's just some lingo I picked up from spending so much time with my friends in the military, and the encryption forums.
BTW, I also highly recommend a program called CCleaner. I use it before I shut down my computer all the time. (I have it set to run automatically before power off.) This program "sanitizes" your computer, and keeps any prying eyes from finding out who you talked to, or where you have been online.