In CHES 2015, a new lightweight block cipher Simeck was proposed that combines good design components of SIMON and SPECK, two lightweight ciphers designed by NSA. As a great tool to improve differential attack, dynamic key-guessing techniques were proposed by Wang et al. that work well on SIMON. In this paper, we convert the dynamic key-guessing techniques to a program that can automatically give out the data in dynamic key-guessing procedure. With our tool, the differential security evaluation of SIMON and Simeck like block ciphers becomes very convenient. We apply the method to Simeck and four members of SIMON family. With a differential of lower Hamming weight we find by Mixed Integer Linear Programming method and differentials in Kolbl et al.’s work, we launch attacks on 21, 22-round Simeck32, 28-round Simeck48 and 34, 35-round Simeck64. Besides, by use of newly proposed differentials in CRYPTO 2015 we get new attack results on 22-round SIMON32/64, 24-round SIMON48/96, 28, 29-round SIMON64/96 and 29, 30-round SIMON64/128. As far as we are concerned, our results on SIMON64 are currently the best results.

Differential Analysis on Simeck and SIMON with Dynamic Key-Guessing Techniques

In the present paper, we analyze the security of SIMON-like ciphers against linear cryptanalysis. First, an upper bound is derived on the squared correlation of SIMON-like round function. It is shown that the upper bound on the squared correlation of SIMON-like round function decreases with the Hamming weight of output mask increasing. Based on this, we derive an upper bound on the squared correlation of linear trails for SIMON and SIMECK, which is 2−2R+2 for any R-round linear trail. We also extend this upper bound to SIMON-like ciphers. Meanwhile, an automatic search algorithm is proposed, which can find the optimal linear trails in SIMON-like ciphers under the Markov assumption. With the proposed algorithm, we find the provably optimal linear trails for 12, 16, 19, 28 and 37 rounds of SIMON32/48/64/96/128. To the best of our knowledge, it is the first time that the provably optimal linear trails for SIMON64, SIMON96 and SIMON128 are reported. The provably optimal linear trails for 13, 19 and 25 rounds of SIMECK32/48/64 are also found respectively. Besides the optimal linear trails, we also find the 23, 31 and 41-round linear hulls for SIMON64/96/128, and 13, 21 and 27-round linear hulls for SIMECK32/48/64. As far as we know, these are the best linear hull distinguishers for SIMON and SIMECK so far. Compared with the approach based on SAT/SMT solvers in [25], our search algorithm is more efficient and practical to evaluate the security against linear cryptanalysis in the design of SIMON-like ciphers.

The Security of SIMON-like Ciphers Against Linear Cryptanalysis.

Dynamic key-guessing techniques, which exploit the property of AND operation, could improve the differential and linear cryptanalytic results by reducing the number of guessed subkey bits and lead to good cryptanalytic results for SIMON. They have only been applied in differential and linear attacks as far as we know. In this paper, dynamic key-guessing techniques are first introduced in integral cryptanalysis. According to the features of integral cryptanalysis, we extend dynamic key-guessing techniques and get better integral cryptanalysis results than before. As a result, we present integral attacks on 24-round SIMON32, 24-round SIMON48/72, and 25-round SIMON48/96. In terms of the number of attacked rounds, our attack on SIMON32 is better than any previously known attacks, and our attacks on SIMON48 are the same as the best attacks.

/pdf/improved-integral-attacks-on-simon32-and-simon48-with-1n5sdpskkc.pdf

Improved Integral Attacks on SIMON32 and SIMON48 with Dynamic Key-Guessing Techniques

SIMECK is a family of three lightweight block ciphers designed by Yang et al., following the framework used by Beaulieu et al. from the United States National Security Agency to design SIMON and SPECK. In this study, the authors employ an improved miss-in-the-middle approach to find zero correlation linear distinguishers and impossible differentials on SIMECK48 and SIMECK64. Based on this novel technique, they will be able to present zero-correlation linear approximations for 15-round SIMECK48 and 17-round SIMECK64 and these zero-correlation linear approximations improve the previous best result by two rounds for SIMECK48 and SIMECK64. Moreover, they attack 27-round SIMECK48 and 31-round SIMECK64 based on these zero-correlation linear distinguishers. In addition, due to the duality of zero-correlation and impossible differential, they search for the impossible differential characteristics for SIMECK48 and SIMECK64 so that they will be able to present 15-round SIMECK48 and 17-round SIMECK64 while the best previously known results were 13-round impossible differentials for SIMECK48 and 15-round impossible differentials for SIMECK64. Moreover, they propose impossible differential attacks on 22-round SIMECK48 and 24-round SIMECK64 based on these impossible differential characteristics. The results significantly improve the previous zero correlation attack and impossible differential characteristic results for these variants of SIMECK to the best of the authors’ knowledge.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-ifs.2016.0590

Improved zero-correlation and impossible differential cryptanalysis of reduced-round SIMECK block cipher

Sensor network services utilize sensor data from low-end IoT devices of the types widely deployed over long distances. After the collection of sensor data, the data is delivered to the cloud server, which processes it to extract useful information. Given that the data may contain sensitive and private information, it should be encrypted and exchanged through the network to ensure integrity and confidentiality. Under these circumstances, a cloud server should provide high-speed data encryption without a loss of availability. In this paper, we propose efficient parallel implementations of Simeck family block ciphers on modern 64-bit Intel processors. In order to accelerate the performance, an adaptive encryption technique is also exploited for load balancing of the resulting big data. Finally, the proposed implementations achieved 3.5 cycles/byte and 4.6 cycles/byte for Simeck32/64 and Simeck64/128 encryption, respectively.

/pdf/secure-data-encryption-for-cloud-based-human-care-services-3twpz9mpsz.pdf

Secure Data Encryption for Cloud-Based Human Care Services

Simeck is a new family of lightweight block cipher proposed by Yang $$et\ al.$$ in CHES'15, which performs efficiently in hardware implementation. In this paper, we search out Simeck's differentials with low Hamming weight and high probability using Kolbl's tool, then exploit the links between differentials and linear characteristics to construct linear hulls for Simeck. We give improved linear hull attack with dynamic key-guessing techniques on Simeck on the basis of round function's property. Our results cover Simeck 32/64 reduced to 23 rounds, Simeck 48/96 reduced to 30 rounds, Simeck 64/128 reduced to 37 rounds, which are the best known results so far for any variant of Simeck.

Lingyue Qin

Papers

Linear Hull Attack on Round-Reduced Simeck with Dynamic Key-Guessing Techniques