A Security Analysis of IoT Encryption: Side-channel Cube Attack on Simeck32/64

Simeck, a lightweight block cipher has been proposed to be one of the encryption that can be employed in the Internet of Things (IoT) applications. Therefore, this paper presents the security of the Simeck32/64 block cipher against side-channel cube attack. We exhibit our attack against Simeck32/64 using the Hamming weight leakage assumption to extract linearly independent equations in key bits. We have been able to find 32 linearly independent equations in 32 key variables by only considering the second bit from the LSB of the Hamming weight leakage of the internal state on the fourth round of the cipher. This enables our attack to improve previous attacks on Simeck32/64 within side-channel attack model with better time and data complexity of 2^35 and 2^11.29 respectively.Comment: 12 pages, 6 figures, 4 tables, International Journal of Computer Networks & Communication

Proposing an MILP-based method for the experimental verification of difference-based trails: application to SPECK, SIMECK

Under embargo until: 2022-07-08Searching for the right pairs of inputs in difference-based distinguishers is an important task for the experimental verification of the distinguishers in symmetric-key ciphers. In this paper, we develop an MILP-based approach to verify the possibility of difference-based distinguishers and extract the right pairs. We apply the proposed method to some published difference-based trails (Related-Key Differentials (RKD), Rotational-XOR (RX)) of block ciphers SIMECK, and SPECK. As a result, we show that some of the reported RX-trails of SIMECK and SPECK are incompatible, i.e. there are no right pairs that follow the expected propagation of the differences for the trail. Also, for compatible trails, the proposed approach can efficiently speed up the search process of finding the exact value of a weak key from the target weak key space. For example, in one of the reported 14-round RX trails of SPECK, the probability of a key pair to be a weak key is 2−94.91 when the whole key space is 296; our method can find a key pair for it in a comparatively short time. It is worth noting that it was impossible to find this key pair using a traditional search. As another result, we apply the proposed method to SPECK block cipher, to construct longer related-key differential trails of SPECK which we could reach 15, 16, 17, and 19 rounds for SPECK32/64, SPECK48/96, SPECK64/128, and SPECK128/256, respectively. It should be compared with the best previous results which are 12, 15, 15, and 20 rounds, respectively, that both attacks work for a certain weak key class. It should be also considered as an improvement over the reported result of rotational-XOR cryptanalysis on SPECK.acceptedVersio

Symmetric block ciphers with a block length of 32 bit

Subject of the thesis at hand is the analysis of symmetric block ciphers with a block length of 32 bit. It is meant to give a comprising overview over the topic of 32 bit block ciphers. The topic is divided in the examination of three questions. It contains a list of state of the art block ciphers with a block length of 32 bit. The block ciphers are being described, focussing on the encryption function. An SPN-based cipher with 32 bit block length is being proposed by rescaling the AES cipher. The 32 bit block length results in certain security issues. These so called risk factors are analysed and mitigating measures are proposed. The result of the thesis is, that 32 bit block ciphers can be implemented in a secure manner. The use of 32 bit ciphers should be limited to specific use-cases and with a profound risk analysis, to determine the protection class of the data to be encrypted

The Simeck Family of Lightweight Block Ciphers

Two lightweight block cipher families, SIMON and SPECK, have been proposed by researchers from the NSA recently. In this paper, we introduce Simeck, a new family of lightweight block ciphers that combines the good design components from both SIMON and SPECK, in order to devise even more compact and efficient block ciphers. For Simeck32/64, we can achieve 505 GEs (before the Place and Route phase) and 549 GEs (after the Place and Route phase), with the power consumption of 0.417 $\mu W$ in CMOS 130nm ASIC, and 454 GEs (before the Place and Route phase) and 488 GEs (after the Place and Route phase), with the power consumption of 1.292 $\mu W$ in CMOS 65nm ASIC. Furthermore, all of the instances of Simeck are smaller than the ones of hardware-optimized cipher SIMON in terms of area and power consumption in both CMOS 130nm and CMOS 65nm techniques. In addition, we also give the security evaluation of Simeck with respect to many traditional cryptanalysis methods, including differential attacks, linear attacks, impossible differential attacks, meet-in-the-middle attacks, and slide attacks. Overall, all of the instances of Simeck can satisfy the area, power, and throughput requirements in passive RFID tags

Linear Cryptanalysis of Reduced-Round SIMECK Variants

SIMECK is a family of 3 lightweight block ciphers designed by Yang et al. They follow the framework used by Beaulieu et al. from the United States National Security Agency (NSA) to design SIMON and SPECK. A cipher in this family with K-bit key and N-bit block is called SIMECKN=K.We show that the security of this block cipher against linear cryptanalysis is not as good as its predecessors SIMON. More precisely, while the best known linear attack for SIMON32/64, using algorithm 1 of Matsui, covers 13 rounds we present a linear attack in this senario which covers 14 rounds of SIMECK32/64. Similarly, using algorithm 1 of Matsui, we present attacks on 19 and 22 rounds of SIMECK48/96 and SIMECK64/128 respectively, compare them with known attacks on 16 and 19 rounds SIMON48/96 and SIMON64/128 respectively. In addition, we use algorithm 2 of Matsui to attack 18, 23 and 27 rounds of SIMECK32/64, SIMECK48/96 and SIMECK64/128 respectively, compare them with known attacks on 18, 19 and 21 rounds SIMON32/64, SIMON48/96 and SIMON64/128 respectively

sLiSCP: Simeck-based Permutations for Lightweight Sponge Cryptographic Primitives

In this paper, we propose a family of lightweight cryptographic permutations called sLiSCP, with the sole aim to provide a realistic minimal design}that suits a variety of lightweight device applications. More precisely, we argue that for such devices the chip area dedicated for security purposes should, not only be consumed by an encryption or hashing algorithm, but also provide as many cryptographic functionalities as possible. Our main contribution is the design of a lightweight permutation employing a 4-subblock Type-2 Generalized-like Structure (GFS) and round-reduced unkeyed Simeck with either 48 or 64-bit block length as the two round functions, thus resulting in two lightweight instances of the permutation, sLiSCP-192 and sLiSCP-256. We leverage the extensive security analysis on both Simeck (Simon-like functions) and Type-2 GFSs and present bounds against differential and linear cryptanalysis. In particular, we provide an estimation on the maximum differential probability of the round-reduced Simeck and use it for bounding the maximum expected differential/linear characteristic probability for our permutation. Due to the iterated nature of the Simeck round function and the simple XOR and cyclic shift mixing layer of the GFS that fosters the propagation of long trails, the long trail strategy}is adopted to provide tighter bounds on both characteristics. Moreover, we analyze sLiSCP against a wide range of distinguishing attacks, and accordingly, claim that there exists no structural distinguishers for sLiSCP with a complexity below $2^{b/2}$ where $b$ is the state size. We demonstrate how sLiSCP can be used as a unified round function in the duplex sponge construction to build (authenticated) encryption and hashing functionalities. The parallel hardware implementation area of the unified duplex mode of sLiSCP-192 (resp. sLiSCP-256) in CMOS $65\,nm$ ASIC is 2289 (resp. 3039) GEs with a throughput of 29.62 (resp. 44.44) kbps, and their areas in CMOS $130\, nm$ are 2498 (resp. 3319) GEs

On the Design Rationale of SIMON Block Cipher: Integral Attacks and Impossible Differential Attacks against SIMON Variants

SIMON is a lightweight block cipher designed by NSA in 2013. NSA presented the specification and the implementation efficiency, but they did not provide detailed security analysis nor the design rationale. The original SIMON has rotation constants of $(1,8,2)$, and Kölbl {\it et al}.~regarded the constants as a parameter $(a,b,c)$, and analyzed the security of SIMON block cipher variants against differential and linear attacks for all the choices of $(a,b,c)$. This paper complements the result of Kölbl {\it et al}.~by considering integral and impossible differential attacks. First, we search the number of rounds of integral distinguishers by using a supercomputer. Our search algorithm follows the previous approach by Wang {\it et al}., however, we introduce a new choice of the set of plaintexts satisfying the integral property. We show that the new choice indeed extends the number of rounds for several parameters. We also search the number of rounds of impossible differential characteristics based on the miss-in-the-middle approach. Finally, we make a comparison of all parameters from our results and the observations by Kölbl {\it et al}. Interesting observations are obtained, for instance we find that the optimal parameters with respect to the resistance against differential attacks are not stronger than the original parameter with respect to integral and impossible differential attacks. We also obtain a parameter that is better than the original parameter with respect to security against these four attacks

Proposing an MILP-based Method for the Experimental Verification of Difference Trails

Search for the right pairs of inputs in difference-based distinguishers is an important task for the experimental verification of the distinguishers in symmetric-key ciphers. In this paper, we develop an MILP-based approach to verify the possibility of difference-based distinguishers and extract the right pairs. We apply the proposed method to some presented difference-based trails (Related-Key Differentials (RKD), Rotational-XOR (RX)) of block ciphers \texttt{SIMECK}, and \texttt{SPECK}. As a result, we show that some of the reported RX-trails of \texttt{SIMECK} and \texttt{SPECK} are incompatible, i.e. there are no right pairs that follow the expected propagation of the differences for the trail. Also, for compatible trails, the proposed approach can efficiently speed up the search process of finding the exact value of a weak-key from the target weak-key space. For example, in one of the reported 14-round RX trails of \texttt{SPECK}, the probability of a key pair to be a weak-key is $2^{-94.91}$ when the whole key space is $2^{96}$; our method can find a key pair for it in a comparatively short time. It is worth noting that it was impossible to find this key pair using a traditional search. As another result, we apply the proposed method %and consider a search strategy for the framework of to \texttt{SPECK} block cipher, to construct longer related-key differential trails of \texttt{SPECK} which we could reach 15, 16, 17, and 19 rounds for \texttt{SPECK32/64}, \texttt{SPECK48/96}, \texttt{SPECK64/128}, and \texttt{SPECK128/256}, respectively. It should be compared with the best previous results which are 12, 15, 15, and 20 rounds, respectively, that both attacks work for a certain weak key class. It should be also considered as an improvement over the reported result of rotational XOR cryptanalysis on \texttt{SPECK}

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

The Simeck family of lightweight block ciphers was proposed in CHES 2015 which combines the good design components from NSA designed ciphers SIMON and SPECK. Dynamic key-guessing techniques were proposed by Wang {\it et al.} to greatly reduce the key space guessed in differential cryptanalysis and work well on SIMON. In this paper, we implement the dynamic key-guessing techniques in a program to automatically give out the data in dynamic key-guessing procedure and thus simplify the security evaluation of SIMON and Simeck like block ciphers regarding differential attacks. We use the differentials from Kölbl {\it et al.}\u27s work and also a differential with lower Hamming weight we find using Mixed Integer Linear Programming method to attack 22-round Simeck32, 28-round Simeck48 and 35-round Simeck64. Besides, we launch the same attack procedure on four members of SIMON family by use of newly proposed differentials in CRYPTO2015 and 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