Information security is an important basis for data protection, even if the perspective is clearly different: information security focuses on the protection of one’s own data and interests, while data protection focuses on the protection of the data subjects and their data and interests, which can sometimes lead to conflicts of interest between data protection and information security. However, the techniques and measures to be applied in both cases overlap in many cases, and this chapter therefore provides an introduction to the relevant aspects of information security. An important part of information security is cryptology, i.e. the science of encryption and decryption, which also plays an important role in data protection, for example, by encrypting data to be protected.