A New Algorithm for the Unbalanced Meet-in-the-Middle Problem

A collision search for a pair of $n$-bit unbalanced functions (one is $R$ times more expensive than the other) is an instance of the meet-in-the-middle problem, solved with the familiar standard algorithm that follows the tradeoff $TM=N$, where $T$ and $M$ are time and memory complexities and $N=2^n$. By combining two ideas, unbalanced interleaving and Oorschot-Wiener parallel collision search, we construct an alternative algorithm that follows $T^2 M = R^2 N$, where $M\le R$. Among others, the algorithm solves the well-known open problem: how to reduce the memory of unbalanced collision search

New Types of Cryptanalytic Attacks Using Related Keys

this paper we described new cryptanalytic attacks which are applicable to the LOKI family of blockciphers and to Lucifer. These new attacks are based on the structure of the key scheduling algorithms. Since we assume that in all the intermediate rounds the data and the subkeys are the same in both executions, with a difference of one (or two) rounds, this attack is independent of the number of the rounds of the cipher. The same attacks could be applicable to DES if only minor changes would be made to the shift pattern of its key scheduling algorithm, and thus these attacks show how so small points in the design of a cipher can contribute to its strength. The results of the related keys attacks are summarized in table 4