## Cryptology ePrint Archive: Report 2011/671

Improved Results on Impossible Differential Cryptanalysis of Reduced-Round Camellia-192/256

Ya Liu and Dawu Gu and Zhiqiang Liu and Wei Li and Ying Man

Abstract: As an international standard adopted by ISO/IEC, the block cipher Camellia has been used in various cryptographic applications. In this paper, we reevaluate the security of Camellia against impossible differential cryptanalysis. Specifically, we propose several 7-round impossible differentials with the $FL/FL^{-1}$ layers. Based on them, we mount impossible differential attacks on 11-round Camellia-192 and 12-round Camellia-256. The data complexities of our attacks on 11-round Camellia-192 and 12-round Camellia-256 are about $2^{120}$ chosen plaintexts and $2^{119.8}$ chosen plaintexts, respectively. The corresponding time complexities are approximately $2^{167.1}$ 11-round encryptions and $2^{220.87}$ 12-round encryptions. As far as we know, our attacks are $2^{16.9}$ times and $2^{19.13}$ times faster than the previously best known ones but have slightly more data.

Category / Keywords: Block Cipher, Camellia, Impossible Differential Cryptanalysis

Date: received 10 Dec 2011, last revised 21 Dec 2011

Contact author: liuya0611 at sjtu edu cn

Available format(s): PDF | BibTeX Citation

Note: We have revised some minor mistakes.

Short URL: ia.cr/2011/671

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