International Association for Cryptologic Research

International Association
for Cryptologic Research

IACR News item: 01 December 2019

Christof Beierle, Alex Biryukov, Luan Cardoso dos Santos, Johann Großschädl, Leo Perrin, Aleksei Udovenko, Vesselin Velichkov, Qingju Wang
ePrint Report ePrint Report
S-boxes are the only source of non-linearity in many symmetric primitives. While they are often defined as being functions operating on a small space, some recent designs propose the use of much larger ones (e.g., 32 bits). In this context, an S-box is then defined as a subfunction whose cryptographic properties can be estimated precisely.

In this paper, we present a 64-bit ARX-based S-box called Alzette, which can be evaluated in constant time using only 12 instructions on modern CPUs. Its parallel application can also leverage vector (SIMD) instructions. One iteration of Alzette has differential and linear properties comparable to those of the AES S-box, while two iterations are at least as secure as the AES super S-box.

Since the state size is much larger than the typical 4 or 8 bits, the study of the relevant cryptographic properties of Alzette is not trivial.
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