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Erschienen in:
2014 | OriginalPaper | Buchkapitel
General Application of FFT in Cryptanalysis and Improved Attack on CAST-256
verfasst von : Long Wen, Meiqin Wang, Andrey Bogdanov, Huaifeng Chen
Erschienen in: Progress in Cryptology -- INDOCRYPT 2014
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Fast Fourier Transformation (FFT) technique was used to reduce the time complexity of linear cryptanalysis by Collard
et al.
at ICISC 2007. This powerful technique has been used to improve the time complexity of zero-correlation linear cryptanalysis as well as integral attack by Bogdanov
et al.
and Todo respectively. Yet whether FFT is applicable when multiple modular additions with subkeys are involved during the partial encryption and decryption phase remains unknown, which has limited its application to some degree. In this paper, we give a general scheme to use FFT technique in linear cryptanalysis, zero-correlation or integral attack where multiple modular additions (together with multiple XORs) with subkeys are involved in the key recovery process. Based on this scheme, we can attack one more round of CAST-256 than the zero-correlation attack on 28-round CAST-256 at ASIACRYPT 2012 by Bogdanov
et al.
, which also becomes the best attack against CAST-256 without any weak key assumption.