" I hate e-mail,” John says. Harvard Li stares him in the eye for a while. “What do you mean?” “The concept is good. The execution is poor. People don’t observe any security precautions. A message arrives claiming to be from Harvard Li, they believe it’s really from Harvard Li. But this message is just a pattern of magnetized spots on a spinning disk somewhere. Anyone could forge it. "

― Neal Stephenson , Cryptonomicon