Communications between devices often passes over public networks that have varying risks of eavesdropping and interference by adversaries. While the endpoints involved in a communications session may be protected, the communications itself might not be. For this reason, cryptography is often employed to make communications unreadable by anyone (or any thing) that may be able to intercept them. Like the courier running an encrypted message through a battlefield in ancient times, an encrypted message in the modern context of computers and the Internet cannot be read by others.
- excerpt from a book in progress
Peter H. Gregory 