Introduction We all have a need for private communication. Whether it’s details of our preparations that we want to share with others in a group, discussing tactics, carrying on trade, or any of a hundred other matters, we should be concerned about keeping our communication private. We should be especially careful when communicating electronically: it’s little more than trivial for a government, a corporation, or even a couple of well-equipped criminals to intercept phone calls, emails, or text messages. We can use encryption, which transforms data into a form that can only be read with a secret key, to help …