This course is an introduction to cryptography, the science of secret writing or, in modern terms, the science of protecting
communication against malicious alterations. The scope of the course is to present the fundamental concepts, methods,
and characteristic techniques of cryptography that are employed in the broad field of information protection. The indispensable
mathematical methods drawn from algebra and number theory are briefly reviewed, to the extent of making the cryptographic
notions fully intelligible. The lectures are mainly theoretical, although the abstract speculations have direct practical applications.

- Historical excursus from ancient to modern times, culminating with the Shannon model of a cryptographic channel.
- Shannon Perfect secrecy in the framework of information theory.
- Definition of the fundamental notions of privacy, integrity, and authentication; motivations and examples of applications.
- Perfect security versus computational security: the notion of computational complexity in cryptography.
- Basic concepts of secret-key and public-key crypto-systems: the notion of one-way function.
- Public-key algorithms: Diffie-Hellman, RSA, Rabin, and El Gamal schemes, and examples of applications, DSS.
- Stream enciphering: stream ciphers and block ciphers, basic principles and structures.
- Encryption Standards: DES and AES.

1) N. Koblitz, A Course in Number Theory and Cryptography, Springer, 1994
2) R. Mollin, An Introduction to Cryptography, Chapman & Hall, 2007
3) F. Fabris, Teoria dell'Informazione, codici, cifrari, Boringhieri, 2001 (in
Italian)
4) M. Elia, Note di Crittografia, WEB site of the Course (in Italian)
5) Excursus on Cryptography, a collection of slides, WEB site of the Course.

The examination consists of written exercises, some of which will be in the form of homework, others under supervision.