The block cipher LBC-3, which was proposed by Nyssanbayeva et al. in 2022, has a 64-bit block size, an 80-bit secret key size, and the number of rounds is 20. The designer investigated the avalanche effect of LBC-3, and Yasushi et al. evaluated the security against differential and linear cryptanalysis. On the other hand, it has not been evaluated the security against integral cryptanalysis, which is one of the most powerful cryptanalysis techniques on block cipher. In this paper, we apply integral cryptanalysis to LBC-3. By establishing the Mixed Integer Linear Programming (MILP) model based on bit-based division property, we discovered the 18-round integral characteristic, the longest integral characteristic of LBC-3. Then, based on the 16-round characteristic newly found, we show that the integral attack on full-round LBC-3 is more efficiently possible with$2^{50.8}$data and$2^{51.4}$times of encryption.

Integral cryptanalysis, which was introduced by Knudsen and Wagner, is one of the most powerful attacks on symmetric key ciphers. Attackers preliminarily search integral characteristics of a target cipher for the key-recovery attack. Todo proposed a novel technique named the division property to find them efficiently. In this paper, we apply this technique to the symmetric key block cipher KASUMI which was developed by modifying MISTY1. It has been used worldwide in the 3rd generation mobile communication networks. As a result, we found new 4.5-round characteristics of KASUMI for the first time. We show that 7-round KASUMI is attackable with 263data complexity and 263.3encryptions under the weak key conditions.

Midori64 proposed by Banik et al. in 2015 is an SPN-type block cipher with 128-bit secret key. The designers have evaluated the security of Midori64 against differential attack, linear attack, boomerang-type attack, impossible differential attacks, and meet-in-the-middle attack by themselves. In this paper, we discuss higher-order differential attack on Midori64, which has not been analyzed yet. Higher-order differential attack proposed by Lai is one of the generic cryptanalysis technique focusing on degree of boolean polynomial of encryption function. As a result, we show the 12th-order differential attack on the 10-round variant of Midori64 where we exploit partial-sum technique proposed by Ferguson and the first-round key assumption called a round-elimination technique. The original Midori64 is secure against our attack because it consists of 16 round functions.

The upper bound of DCPmaxis a security index of a cipher against differential cryptanalysis. It is usually evaluated by a truncated-path search with Viterbi algorithm. The search often gives an imaginary path as the resultant optimum one in generalized Feistel-type cipher, which cannot be connected as a real path. We discuss the phenomenon on example base, and propose a new search method to avoid such imaginary paths. Our method is based on carrying over a constraint equation in state transition, and can give the tighter upper bound of DCPmaxthan conventional one.

Enocoro is a family of stream ciphers proposed by Watanabe et al. in 2007. It consists of two algorithms called Enocoro-80 and Enocoro-128v1.1, whose key lengths are 80 bits and 128 bits respectively. In this paper, we show that Enocoro-128v1.1 is vulnerable against the related-key attack in which we assume a stronger attacker than one in the related-key differential attack. The attack is applicable with 2112out of 2128keys and the calculation complexity of the attack is about 265. Our attack is mainly of theoretical interest and do not present a threat to practical applications using Enocoro-128v1.1. In addition, we propose to update Enocoro-128v1.1 to Enocoro-128v2 where a patch has been applied to prevent the attack.

We theoretically analyze the performance of coherent ultrashort light pulse code-division multiple-access (CDMA) communication systems with nonlinear optical thresholders. The coherent ultrashort light pulse CDMA is one of the promising systems for optical local area networks due to the advantages of asynchronous transmission, high information security, multiple access capability, and optical processing. The nonlinear optical thresholder is based on frequency chirping induced by self-phase modulation (SPM) in optical fibers, and discriminates the ultrashort pulse from multiple access interference (MAI) having picosecond duration. Our results show that the nonlinear optical thresholder can discriminate 400-fs ultrashort pulse from /spl ap/100-ps MAI even if the response time of the photodetector is limited to 100-ps, and that the system performance does not always become better as the total number of users becomes smaller because of thermal noise, which is a unique characteristic of this system.