Historically, cryptography was used to ensure private communication between two people with some prior relationship. More recently, its scope has expanded to include things as diverse as data integrity, secure internet-wide communication, electronic cash, secure distributed computation, and more. Cryptography has also become ubiquitous. Perhaps unknowingly, we have all encountered applications of cryptography in our daily lives---whether by logging in using a password, making a web purchase over a secure connection, or applying a software update that is digitally signed.