this is for holding javascript data
Massimiliano Sala edited bits4.tex
about 6 years ago
Commit id: e1caca9df5b5f457e72577ddd26044cedac50378
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index f14aab4..68dbf2a 100644
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...
(we do not prove this last claim, leaving it as a useful exercise to the reader).
\\ Now, pointing out that the size of $B_3$ is $\vert B_3 \vert =
\vert(\Fb )^3 \vert = 2^8$, so there are as many functions in $B_3$ as the number of
possible
ANFs, ANF's, we get that
$$\{f:(\Fb)^3 \rightarrow \Fb \textrm{ with ANF}\}
= B_3,$$ \; =\; B_3 \,,$$
hence every function from $(\Fb)^3$ to $\Fb$ can be written in Absolute Normal Form.
%
\begin{Example}
Consider the function $f:(\Fb)^3 \rightarrow \Fb$
defined by \\
...
$f (x, y, z) = x + y$
\end{Example}
The following function, often used in cryptography, is called
the \emph{majority function}:
$$f: (\Fb)^3 \rightarrow \Fb $$
$$(x,y,z)\mapsto xy+xz+yz.$$
This function returns value $1$ if and only if the majority among the input bits $x$, $y$ and $z$ holds value $1$ and $0$ otherwise i.e. if and only if the majority among the input bits $x$, $y$ and $z$ holds value $0$.