New Characterizations for the Multi-output Correlation-Immune Boolean Functions.

In stream ciphers, the correlation-immune functions serve as an important metric for measuring a cryptosystem resistance against correlation attacks. In block ciphers, there is a equivalence between multipermutations and correlation-immune functions. In this paper, three new methods are proposed to characterize the multioutput correlation-immune Boolean functions. Compared with the Walsh spectral characterization method, the first method can significantly reduce the computational complexity. The last two characterization methods are in terms of the Fourier spectral characterizations over the complex field. Furthermore, only one point of the Fourier spectra needs to be calculated when characterize a symmetric multi-output correlation-immune Boolean function.