Modified Cryptanalysis of RC5

The RC5 encryption algorithm was designed by Roland Rivest in 1994. Since its publication, RC5 has attracted the attention of many researchers in the cryptographic community in efforts to accurately assess the security offered. 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 modified these results due to a differential approach. The attack requires 234 chosen plaintexts. We show that the 64 bit word version of RC5 is also weaker than it was expected.