共通鍵暗号の精密解析に関する研究

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1. To implement robust and secure pseudo-random number generators (PRNG) is a challenging issue for low-cost Radio-frequency identification (RFID) tags. In this first research, we study the security of LFSR-based PRNG implemented on EPC Gen2 tags and exploit LFSR-based PRNG to provide a better constructions. We provide a cryptanalysis against the J3Gen which is LFSR-based PRNG and proposed by Sugei et al. for EPC Gen2 tags using distinguish attack and make observations on its input using NIST randomness test. We also test the PRNG in EPC Gen2 RFID Tags by using the NIST SP800-22. As a counter-measure, we propose two modified models based on the security analysis results. We show that our results perform better than J3Gen in terms of computational and statistical property.2. Integral attack can be considered as the deterministic version of the statistical saturation attack,which works by tracing the properties of the integral sets after certain rounds of encryption.In this second research, we provide the first study on how to take advantage of the integral attack and apply it to cryptanalysis by using statistical approach. One of our contributions is to firstly apply the internal collision of a set as the evaluated statistics and show how this property can be efficiently propagated in the General Feistel Structure (GFS) with bijective map S-Box. Secondly, we provide a simple statistical framework to evaluate the data complexity. Finally, we evaluate several GFS and find out for some of the designs, our approach provide a better result compared with other statistical attack.