Abstract
RC5 is a fast block cipher designed by Ron Rivest in 1994. Since then several attempts of cryptanalysis of this cipher were published. The best previously known attack requires 254 chosen plaintexts in order to derive the full set of 25 subkeys for the 12 round RC5 with 32 bit words. In this paper we show a drastic improvement of these results due to a novel partial differential approach. Our attack requires 244 chosen plaintexts. We show that the 64 bit word version of RC5 is also much weaker than it was expected.
As of today no known-plaintext attack on RC5, even with reduced number of rounds exists due to recent result [9] which found gaps in the linear attack on RC5 described in [3].
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Biryukov, A., Kushilevitz, E. (1998). Improved cryptanalysis of RC5. In: Nyberg, K. (eds) Advances in Cryptology — EUROCRYPT'98. EUROCRYPT 1998. Lecture Notes in Computer Science, vol 1403. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0054119
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DOI: https://doi.org/10.1007/BFb0054119
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