Given the diversity of the digital terrain, data is rarely encrypted from start to finish. Even when data is encrypted in transit from one computer to another in a network, it often must be decrypted at each point and reencrypted when handed off to the next computer. If any of these way stations—whether a PC, a Web server or a piece of networking equipment—is not well protected, unencrypted data is left vulnerable to prying eyes.
Fact or Fiction: Encryption Prevents Digital Eavesdropping: Scientific American
Staying out of PRISM, etc.