Bart Mennink

Paper 2024/557 , Radboud University Nijmegen , Radboud University Nijmegen Abstract Hash chain based password systems are a useful way to guarantee authentication with one-time passwords. The core idea is specified in RFC 1760 as S/Key. At CCS 2017, Kogan et al. introduced T/Key, an improved password system where one-time passwords are only valid for a limited time period. They proved security of their construction in the random oracle model under a basic modeling of the adversary.

Paper 2024/407 , Radboud University, Nijmegen , Radboud University, Nijmegen Abstract It is known that the sponge construction is tightly indifferentiable from a random oracle up to around $2^{c/2}$ queries, where $c$ is the capacity. In particular, it cannot provide generic security better than half of the underlying permutation size. In this paper, we aim to achieve hash function security beating this barrier. We present a hashing mode based on two $b$-bit permutations named the double sponge.

Paper 2024/084 , Intel (United States) , Intel (Poland) , Radboud University Nijmegen , Intel (Poland) A tweakable wide blockcipher is a construction which behaves in the same way as a tweakable blockcipher, with the difference that the actual block size is flexible. Due to this feature, a tweakable wide blockcipher can be directly used as a strong encryption scheme that provides full diffusion when encrypting plaintexts to ciphertexts and vice versa.