Biblio

These days the digitization process is everywhere, spreading also across central governments and local authorities. It is hoped that, using open government data for scientific research purposes, the public good and social justice might be enhanced. Taking into account the European General Data Protection Regulation recently adopted, the big challenge in Portugal and other European countries, is how to provide the right balance between personal data privacy and data value for research. This work presents a sensitivity study of data anonymization procedure applied to a real open government data available from the Brazilian higher education evaluation system. The ARX k-anonymization algorithm, with and without generalization of some research value variables, was performed. The analysis of the amount of data / information lost and the risk of re-identification suggest that the anonymization process may lead to the under-representation of minorities and sociodemographic disadvantaged groups. It will enable scientists to improve the balance among risk, data usability, and contributions for the public good policies and practices.

Implementations of ARX ciphers are hoped to have some intrinsic side channel resilience owing to the specific choice of cipher components: modular addition (A), rotation (R) and exclusive-or (X). Previous work has contributed to this understanding by developing theory regarding the side channel resilience of components (pioneered by the early works of Prouff) as well as some more recent practical investigations by Biryukov et al. that focused on lightweight cipher constructions. We add to this work by specifically studying ARX-boxes both mathematically as well as practically. Our results show that previous works' reliance on the simplistic assumption that intermediates independently leak (their Hamming weight) has led to the incorrect conclusion that the modular addition is necessarily the best target and that ARX constructions are therefore harder to attack in practice: we show that on an ARM M0, the best practical target is the exclusive or and attacks succeed with only tens of traces.

π-Cipher is one of the twenty-nine candidates in the second round of the CAESAR competition for authenticated ciphers. π-Cipher uses a parallel sponge construction, based upon an ARX permutation. This work shows several state recovery attacks, on up to three rounds. These attacks use known values in the function's bitrate, combined with values found through exhaustive search, to retrieve the remaining values in the internal state. These attacks can break one round, for any variant of π-Cipher, in negligible time. They can also break two or three rounds much faster than exhaustive search on the key, for some variants. However, these attacks only work against version 1 of π-Cipher, due to the differences in the padding function for version 2.0. To fill this gap, this work also includes a one round attack against version 2.0, building upon the distinguisher present in the π-Cipher submission document.