From highly sensitive material to an emoji-filled text messages, we expect all of our communications to be private in this day and age. That wouldn't be possible without codes, ciphers and cryptography.
Over the years, cryptography has gone from simple letter-shifting to deep, uncrackable protections that can't be broken by the most sophisticated codebreakers. It's been necessary, to keep unwanted eyes out, but it has taken some real innovation to make it happen.
Encryption has been improved over the years by many, many people, some of whom are featured here — experts such as Phil Zimmermann, Whitfield Diffie, Steven Levy, Andrew Hodges and Alex Stamos.