Information Technology Reference
In-Depth Information
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 signa-
ture
, 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 how to go about signing and encrypting messages in Mail.
Learn When and Why to Sign or Encrypt Messages
Let me start with the essential question of whether, or under what circumstances, you should
even think about signing or encrypting messages. It's not something everyone needs to do, and
if you never need to do it, you need not bother reading the rest of this chapter. But the need
could arise at some point—and even if you don't
need
to sign or encrypt, you may find that
there are some benefits to doing so.
Most of us are accustomed to thinking of email as being private. One person sends a message
and someone else receives it; as long as no one is looking over either person's shoulder or
snooping on their computers when they're not around, we presume that whatever was in that
message is known only to the sender and recipient.
Indeed, that's how things work
most
of the time, just as with paper letters:
Most
of the time no
one except the intended recipient opens a letter to see what's inside. But mail theft, tampering,
accidents, and honest mistakes do occur. It sometimes happens that a person who shouldn't
see what's inside an envelope, does. And when the contents of that envelope are highly confid-
ential, sensitive, or valuable, someone else reading your mail can become a serious problem
indeed.
Email is no different. It should be private, but it isn't always. Each message exists not only
on the computer of the sender and recipient, but also (at least temporarily) on each party's
mail server. In addition, a message may pass through any number of intermediate servers and
routers, and may be backed up along the way in the data centers of one or more ISPs. In any
