A provably secure countermeasure against first order side-channel attacks was proposed by Nikova et al. (P. Ning, S. Qing, N. Li (eds.) International conference in information and communications security. Lecture notes in computer science, vol. 4307, pp. 529-545, Springer, Berlin, 2006). We have implemented the lightweight block cipher PRESENT using the proposed countermeasure. For this purpose we had to decompose the S-box used in PRESENT and split it into three shares that fulfill the properties of the scheme presented by Nikova et al.

We present a new characterization of semi-bent and bent quadratic functions on finite fields. First, we determine when a GF (2)-linear combination of Gold functions T r(x 2 i +1 ) is semi-bent over GF (2 n ), n odd, by a polynomial GCD computation. By analyzing this GCD condition, we provide simpler characterizations of semi-bent functions. For example, we deduce that all linear combinations of Gold functions give rise to semi-bent functions over GF (2 p ) when p belongs to a certain class of primes. Second, we generalize our results to fields GF (p n ) where p is an odd prime and n is odd. In that case, we can determine whether a GF (p)-linear combination of Gold functions T r(x p i +1 ) is (generalized) semi-bent or bent by a polynomial GCD computation. Similar to the binary case, simple characterizations of these p-ary semi-bent and bent functions are provided.

Abstract. In this article, we propose a new comparison metric, the figure of adversarial merit (FOAM), which combines the inherent security provided by cryptographic structures and components with their implementation properties. To the best of our knowledge, this is the first such metric proposed to ensure a fairer comparison of cryptographic designs. We then apply this new metric to meaningful use cases by studying Substitution-Permutation Network permutations that are suited for hardware implementations, and we provide new results on hardware-friendly cryptographic building blocks. For practical reasons, we considered linear and differential attacks and we restricted ourselves to fully serial and round-based implementations. We explore several design strategies, from the geometry of the internal state to the size of the S-box, the field size of the diffusion layer or even the irreducible polynomial defining the finite field. We finally test all possible strategies to provide designers an exhaustive approach in building hardware-friendly cryptographic primitives (according to area or FOAM metrics), also introducing a model for predicting the hardware performance of round-based or serial-based implementations. In particular, we exhibit new diffusion matrices (circulant or serial) that are surprisingly more efficient than the current best known, such as the ones used in AES, LED and PHOTON.

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Abstract. In this paper, we study and compare two popular methods for post-processing random number generators: linear and Von Neumann compression. We show that linear compression can achieve much better throughput than Von Neumann compression, while achieving practically good level of security. We also introduce a concept known as the adversary bias which measures how accurately an adversary can guess the output of a random number generator, e.g. through a trapdoor or a bad RNG design. Then we prove that linear compression performs much better than Von Neumann compression when correcting adversary bias. Finally, we discuss on good ways to implement this linear compression in hardware and give a field-programmable gate array (FPGA) implementation to provide resource utilization estimates.