content: Yes. Look into something called PGP. You make a private key and a public key. You give people you want to be able to decrypt your messages the public key. You put a password on the private key and give it to nobody. Then you collect public keys from people you want to be able to talk to. Then you type whatever you want in a program that supports it, I use pgp4USB, and then encrypt it with the public key of whoever you are talking to. Then they take your encrypted message and put it in a program that has their private key stored in it and they decrypt it with that, which requires their password. The same thing applies to you when they give you messages encrypted with your key.  The only way to read messages ebcrypted with public keys is to have the corresponding private key that belongs to it.