Cryptanalysis of Selected Block Ciphers with Highlight on SIMON

Seminar / Lecture
For NYU Community

Speaker: Hoda A Alkhzaimi, Abu Dhabi faculty candidate

The escalation of ubiquitous and pervasive computing as in RFID, sensor networks and networks based on Internet of Things (IoT) in the past years have drove most of the implementations within these environments to utilize designs for restricted hardware and software parameters. The introduced restrictions in the form of low-cost, low energy and low computations devices, among others, within these environments made it essential to shift the design of the standard cryptographic primitives used to provide security to satisfy the restricted performance parameters while maintain an equivalent level of security within the provided cryptosystems for these environments. Thus, the design of lightweight primitives has been a critical contribution of the research community to bridge the gap between standard designs and restrictive lightweight demands. In this talk we will revisit different lightweight block ciphers designs and their cryptanalytic results that will give us an intuition on the different design approaches and limitations if any.

We will specifically look into differential and linear cryptanalytic results for SIMON block cipher in addition to utilizing the links between different cryptanalytic approaches. Simon is the first of twofamilies of ten lightweight block ciphers published by Beaulieu et al. from U.S. National Security Agency (NSA). In this research we investigated the security of SIMON against different variants of differential and linear cryptanalysis techniques, for example classical and multiple linear cryptanalysis and linear hulls. We presented a connection between linear- and differential- characteristics as well as differentials and linear hulls in SIMON. We used that link to derive results in the linear settings of SIMON from current known differential results.

In addition to finding a single-characteristic based linear approximations, we additionally investigated the effect of the linear hulls in SIMON by finding better approximations that enable us to improve the previous results. Our best linear cryptanalysis employs average squared correlation of the linear hull of SIMON based on correlation matrices. The result covers 21 out of 32 rounds of SIMON32/64 with respective time and data complexity of 2^{54.5} and 2^{30.5}. We have implemented our attacks for small scale variants of SIMON and our experiments confirm the theoretical biases and correlation presented in this work.

The results presented are a collaborative research with different researchers Abdelraheem et al and Bing Sun et al. Some of the results were published in Crypto 2015 and IndoCrypt 2015.

Bio: Hoda A. Alkhzaimi served in different posts for research and development in Cyber Security and Cryptology for the past ten years. She headed the Department of Research and Development for Cyber Security and Cryptology in different national initiatives in the United Arab Emirates along with her associations to different security initiatives nationally and internationally. Alkhzaimi has a specific expertise in cryptology; cryptanalysis, constructing and validating security hardware and software components, constructing trusted security architectures for different environments in different products for the respective industries. Hoda A.Alkhzaimi obtained her PhD in Cryptanalysis from Denmark Technical University. Her current research interests include constructing and analyzing cryptographic primitives, validating and investigating links between different cryptanalytic approaches and utilizing cryptographic primitives in different cyber security architectures as in Internet of Things and big data analysis among others.