In this chapter, we consider some of the cryptography which can be used to protect data stored on personal devices. We begin by looking at various forms of cryptographic file protection, including full disk encryption. We then consider the cryptography which can be used to support two applications widely used on personal devices, namely, email and asynchronous messaging. To illustrate the latter, we discuss the cryptography deployed by the application WhatsApp. Finally, we obtain a slightly different perspective by providing an overview of the cryptography supported by one particular device platform, Apple’s iOS operating system.