Learn how encryption keeps online information private in this video from the NOVA Cybersecurity Lab. Your messages are coded by email programs and websites to prevent others from reading them. Codes have been used in messages for centuries.  Caesar sent coded messages to his military in ancient Rome. In the 1940s, the Allied forces cracked the German Enigma Code, saving lives during World War II. Today, emails are protected through public-key cryptography, which uses numbers from both the sending and receiving email servers to create a key. However, not all online activity is encrypted and in some cases your browsing history, text messages, and data from apps can be intercepted.