RC5: Day 9

The RC5 Encryption Algorithm

This document describes the RC5 encryption algorithm, a fast symmetric block cipher suitable for hardware or software implementations. A novel feature of RC5 is the heavy use of data-dependent rotations. RC5 has a variable word size, a variable number of rounds, and a variable-length secret key. The encryption and decryption algorithms are exceptionally simple.

Day 9: Topic Models

C Filter for Rc5

In this appendix we present an eecient implementation of the lter described in Section 3.1. One must place ciphertext diierences after (2r ?1)th round (one half-round before the last half-round) into DLevel + 1] and DLevel] before calling the lter. These diierences can be calculated (for RC5) from the known ciphertext diierences and the known rotation amount of the last round. A call to the lte...

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 2 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 mod...

Improved Correlation Attack on RC5

Various attacks against RC5 have been analyzed intensively([1], [2], [4]–[7]). A known plaintext attack([2]) has not been reported that it works on so higher round as a chosen plaintext attack([1]), but it can work more efficiently and practically. In this paper we investigate a known plaintext attack against RC5 by improving a correlation attack ([7]). As for a known plaintext attack against R...