Cryptology From paper and pencil, mechanical devices to computers

1. Time changes: Earlier secret tactical com-munication involving few people are replaced by other environments and applications due to computers. Electronic commerce, www-communication, and mobile communication introduce other needs that we try to satisfy with cryptographic methods. Crypto-based methods are a mean för achieving these goals. Analyses of classical ciphers are often based on results from probability theory while modern public-key methods are based on number theory and abstract algebra. Designing a whole system correctly is very difficult. It is a well-known fact that many standard methods have weaknesses making them easy to ”crack”. CryptologyFrom paper and pencil, mechanical devices to computers • We would like to: • ensure confidentiality (as above) • be sure sure that information has not been tampered with (integrity) • know that the data origin is authentic • be convinced that the user is as claimed (identification) • stop a sender from denying messages sent (non-repudiation) A real classical cipher. Spartan, circa 2500 years of age. Preresquisites: Algorithms and data structures, operating systems, and algebra. Goal: To convey knowledge and abilities on algorithms and protocols for the services listed on the left.