Boomerang Spectra of Two Classes of Power Functions via Their Differential Spectra
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In EUROCRYPT 2018, Cid et al. introduced a new concept on the cryptographic property of S-boxes to evaluate the subtleties of boomerang-style attacks. This concept was named as boomerang connectivity table (BCT for short) . For a power function, the distribution of BCT can be directly determined by its boomerang spectrum. In this paper, we investigate the boomerang spectra of two classes power functions over even characteristic finite fields via their differential spectra. The boomerang spectrum of the power function x^2^m+1 - 1 over 𝔽_2^2m is determined, where 2^m+1-1 is a kind of Niho exponent. The boomerang spectrum of the Gold function G(x)=x^2^t+1 over 𝔽_2^n is also determined. It is shown that the Gold function has two-valued boomerang spectrum.
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