Multidimensional Zero-Correlation Linear Cryptanalysis of the Block Cipher KASUMI
This work addresses security concerns for users of wireless standards like 3GPP that rely on KASUMI, but it is incremental as it builds on existing cryptanalytic methods.
The paper tackled the security evaluation of the block cipher KASUMI against zero-correlation linear attacks, proposing a 6-round attack requiring about 2^85 encryptions and 2^62.8 known plaintexts, and a 7-round attack under weak key conditions with about 2^110.5 encryptions and 2^62.1 known plaintexts.
The block cipher KASUMI is widely used for security in many synchronous wireless standards. It was proposed by ETSI SAGE for usage in 3GPP (3rd Generation Partnership Project) ciphering algorthms in 2001. There are a great deal of cryptanalytic results on KASUMI, however, its security evaluation against the recent zero-correlation linear attacks is still lacking so far. In this paper, we select some special input masks to refine the general 5-round zero-correlation linear approximations combining with some observations on the $FL$ functions and then propose the 6-round zero-correlation linear attack on KASUMI. Moreover, zero-correlation linear attacks on the last 7-round KASUMI are also introduced under some weak keys conditions. These weak keys take $2^{-14}$ of the whole key space. The new zero-correlation linear attack on the 6-round needs about $2^{85}$ encryptions with $2^{62.8}$ known plaintexts. For the attack under weak keys conditions on the last 7 round, the data complexity is about $2^{62.1}$ known plaintexts and the time complexity $2^{110.5}$ encryptions.