Mac OS Utilities
Guard7 is a general purpose cryptography tool that can be used to encrypt, decrypt email, file, sign and verify files. It is the graphical frontend for the GNU Privacy Guard (GnuPG or GPG, http://www.gnupg.org) with additional features. Guard7 is an encryption and decryption system based on industry standard that can ensure the complete security of business negotiations or personal messages. It was developed to make the daily work with GnuPG easy and simple.
The most difference between "public key cryptography" and normal "password protected cryptography" is that the first approach don't ask you to distribute any password to anyone or any unsafe place, e.g. email, chat app, or internet. And, you need an encryption tool that has industrial strength to protect your confidential information.