Sign and Encrypt Messages
Back in Signatures, I explained how to add a signature to the end of each message with your contact information, a quote, or other content. But a message can also have a digital signature, a (normally invisible) string of characters that confirms to the recipient that the message truly comes from the address it appears to come from, and that the message contents haven’t been altered in transit.
In addition, Mail can encrypt messages, scrambling their contents so that only someone with the necessary key (presumably, the recipient) can view their contents, thereby ensuring private communications.
In this chapter I discuss if and when you should use digital signatures and encryption, how they work behind the scenes, and ...