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    "Improved Correlation Attack on RC5"

    Biham and Shamir proposed a differential cryptanalysis, which can break DES more efficient than a brute force attack(i.e. an exhaustive search) in 1990. Since the differential cryptanalysis were proposed, many researchers have been focused on cryptanalysis. Recently, Knudsen-Meier proposed a new cryptanalysis on RC6 which is based on a correlation using chi^2-test. Moreover, Shimoyama et al. presented to apply the correlation attack to RC5.
    In this paper, I proposed an improved correlation attack based on the characteristics that target bits of chi^2-value are not only least significant four bits but also any four bits. By using this attack algorithm, my experimental results show that we can recover least significant four bits of secret extended key in final round on RC5 reduced to 20half-round with probability of more than 90%. Finally, I show a result of experimental on recovering 31-bits(is not including MSB) final half-round key.

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