Cryptology ePrint Archive: Report 2021/390

Orthros: A Low-Latency PRF

Subhadeep Banik and Takanori Isobe and Fukang Liu and Kazuhiko Minematsu and Kosei Sakamoto

Abstract: We present Orthros, a 128-bit block pseudorandom function. It is designed with primary focus on latency of fully unrolled circuits. For this purpose, we adopt a parallel structure comprising two keyed permutations. The round function of each permutation is similar to Midori, a low-energy block cipher, however we thoroughly revise it to reduce latency, and introduce different rounds to significantly improve cryptographic strength in a small number of rounds. We provide a comprehensive, dedicated security analysis. For hardware implementation, Orthros achieves the lowest latency among the state-of-the-art low-latency primitives. For example, using the STM 90nm library, Orthros achieves a minimum latency of around 2.4 ns, while other constructions like PRINCE, Midori-128 and QARMA_{9}-128-\sigma_{0} achieve 2.56 ns, 4.10 ns, 4.38 ns respectively.

Category / Keywords: secret-key cryptography / Pseudorandom Function, Low Latency, Lightweight Cryptography, Sum of Permutations

Original Publication (with minor differences): IACR-FSE-2022

Date: received 23 Mar 2021

Contact author: subhadeep banik at epfl ch,takanori isobe@ai u-hyogo ac jp,liufukangs@gmail com,k-minematsu@nec com,k sakamoto0728@gmail com

Available format(s): PDF | BibTeX Citation

Note: This is the revised version of the paper published from ToSC 2021 Issue 1. We revise some typos in the formula of the S-box from in Sect. 3.3. Other contents are the same as the original version.

Version: 20210327:071345 (All versions of this report)

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