## Cryptology ePrint Archive: Report 2000/005

On Resilient Boolean Functions with Maximal Possible Nonlinearity

Yuriy Tarannikov

Abstract: It is proved that the maximal possible nonlinearity of $n$-variable $m$-resilient Boolean function is $2^{n-1}-2^{m+1}$ for ${2n-7\over 3}\le m\le n-2$. This value can be achieved only for optimized functions (i.~e. functions with an algebraic degree $n-m-1$). For ${2n-7\over 3}\le m\le n-\log_2{n-2\over 3}-2$ it is suggested a method to construct an $n$-variable $m$-resilient function with maximal possible nonlinearity $2^{n-1}-2^{m+1}$ such that each variable presents in ANF of this function in some term of maximal possible length $n-m-1$. For $n\equiv 2\pmod 3$, $m={2n-7\over 3}$, it is given a scheme of hardware implementation for such function that demands approximately $2n$ gates EXOR and $(2/3)n$ gates AND.

Category / Keywords: secret-key cryptography / boolean functions, stream ciphers, secret-key cryptography, implementation