Block Ciphers and Encryption Schemes.

Snowden's alarming disclosures on NSA's global surveillance are an evidence of the paramount importance of cryptography to our daily lives. Also, attacks on widely used functions such as SHA-1 triggered international competitions for cryptographic functions. This project is about encryption, ranging from the construction of block ciphers (basic mathematical building blocks) to various types of encryption schemes. Encryption finds a wide range of real-world applications, such as banking, the world wide web, voting, and mobile phones. In these applications the goal of encryption is to provide secrecy and authenticity, but they are often also required to offer additional functionalities. Numerous encryption schemes exist, and yet, the security fundament is rather limited. The goal of this project is threefold. Firstly, we derive generalized security models and identify which models are the right ones for which purposes. The goal is to introduce security models that are general enough to imply older ones, that cover a wide range of encryption schemes, and that allow for a clearer understanding of the needs in the area of encryption. Secondly, employing the new models, we target sharp security bounds of existing ciphers and schemes. The third objective is to design, along the lines of the improved security models, constructions that achieve good provable security and are efficient in use. In general, we aim at a solid provable security fundament for widely used encryption schemes.