Cryptology

This chapter focuses on extending the encoding scheme to cases in which the transmitted information contains a secret. Cryptology ‐ literally “science of secret” ‐ consists of two main components, namely cryptography, which deals with studying and building processes for information encryption, and cryptanalysis, which deals with analyzing cipher‐texts in order to recover the hidden information. The chapter presents how to build secure systems, and this requires the knowledge of defense as well as attack techniques, in order to develop a global strategy of security. It discusses the possible threats and derives general cryptography principles. Two types of ciphers are developped: secret key cryptography that mimics perfect secrecy in realistic settings and public key cryptography that eases key exchanges. The chapter develops the authentication of a sender and electronic signature. Finally, it ends with the study of several usual protocols for secure information exchanges.