Antonio Flórez-Gutiérrez
NTT Social Informatics Laboratories

Lorenzo Grassi
RUB

Gregor Leander
RUB

Ferdinand Sibleyras
NTT Social Informatics Laboratories

Yosuke Todo
NTT Social Informatics Laboratories

Keywords:

Abstract

We introduce a new approach between classical security proofs of modes of operation and dedicated security analysis for known cryptanalysis families: General Practical Cryptanalysis. This allows us to analyze generically the security of the sum of two keyed permutations against known attacks. In many cases (of course, not all), we show that the security of the sum is strongly linked to that of the composition of the two permutations. This enables the construction of beyond-birthday bound secure low-latency PRFs by cutting a known-to-be-secure block cipher into two equal parts. As a side result, our general analysis shows an inevitable difficulty for the key recovery based on differential-type attacks against the sum, which leads to a correction of previously published attacks on the dedicated design Orthros.