Tampering in wonderland

Cryptography (originally meaning “the art of secret communication”) is an ancient discipline born in the past to satisfy some needs of the human being. Today the world “cryptography” has a much broader meaning. In fact, the development of the digital era (mainly due to the introduction of the digital calculators) and later on of the Internet have created new scenarios of communications, generating intriguing challenges for modern “cryptographers”. In the past (say before the 80’s) the development of a “secure” system was mostly based on intuition and experience. This approach led to a cut-and-mouse game in which new schemes were proposed and (immediately after) new attacks against them were found. A milestone in the development of a solid mathematical theory—turning cryptography from an art into a real science—is an approach due to Goldwasser and Micali called “provable security”. The goal of this approach is to state rigorous definitions of what “secure” means in a given context and build cryptographic primitives able to satisfy these definitions in a provable way. This is indeed a very strong guarantee. It should be clear that the way one defines security is crucial for the results being meaningful. In particular our mathematical model of reality should be as close as possible to the real world, catching all possible attacks out there. Unfortunately, it turned out that this is not always the case. There are in fact attacks—so called side-channel attacks—which can be applied to an actual implementation of a device and not to its mathematical abstraction. These attacks have been shown to be very powerful, completely compromising security of otherwise provably secure schemes. A modern trend in theoretical cryptography is to try filling this gap between theory and practice, building primitives which maintain their provably secure guarantees even in the presence of a powerful adversary able to apply sidechannels. This area of research is evolving continuously and very quickly. The thesis you are reading deals with some of these challenges and summarises recent achievements in this topic.