Access cryptographic secure random generator

Question

I am writing my Master's Thesis in cryptography at the moment. The main part deals with randomness; therefore, I wanted to make a little Tikz picture in the introduction to show an example of randomness. Of course, I could create a random string somewhere else and just import it to LaTeX, but this approach feels unsatisfying. My question: Is there a way to access a cryptographic secure random number generator directly from LaTeX, e.g. within a Tikz picture? I assume my solution using random() from pgf math is not cryptographic secure:

\documentclass{article}
\usepackage{tikz}

\begin{document}

\begin{center}
        \begin{tikzpicture}
            \foreach \row in {0,1,...,7}{
                \foreach \column in {0,1,...,7}{
                    \pgfmathparse{random(0,1)}
                    \ifnum\pgfmathresult=1
                        \draw[fill, black] (\row, \column) rectangle (\row +1, \column + 1);
                    \fi
                }
            }
        \end{tikzpicture}
    \end{center}

\end{document}

Edit: To be more accurate on the secure part: I am searching for a random generator, that is accepted as a standard, e.g. by Nist. For those more interested in the topic, here is a reference.

Answer 1

You can use -shell-escape to make a call to some program on your platform that implements a CSPRNG.

In the following example, I use /dev/urandom via od using a suggestion from Heitor's log, because /dev/urandom on macOS uses Fortuna.

\documentclass{article}

\ExplSyntaxOn

\NewDocumentCommand{\settorandomnumber}{m}
 {% #1 = macro to be set
  \sys_get_shell:nnN
   { od ~ -vAn ~ -N4 ~ -t ~ u4 ~ < ~ /dev/urandom } % execute
   { \endlinechar=-1 } % ignore endline
   \l_tmpa_tl % store in
  \tl_set:Nx #1 { \fp_eval:n { \l_tmpa_tl / (2^32) } } % normalize
 }

\ExplSyntaxOff

\begin{document}

\settorandomnumber\pgfmathresult \pgfmathresult

\settorandomnumber\pgfmathresult \pgfmathresult

\settorandomnumber\pgfmathresult \pgfmathresult

\settorandomnumber\pgfmathresult \pgfmathresult

\end{document}

The call to od generates a random integer between 0 and 2³² − 1 (inclusive), and we can divide to get a number in the interval [0,1).

Here's also a “random bit generator”: we can generate just a one-byte number and check whether it's larger than 127.

\documentclass{article}

\ExplSyntaxOn

\NewDocumentCommand{\settorandomnumber}{m}
 {% #1 = macro to be set
  \sys_get_shell:nnN
   { od ~ -vAn ~ -N4 ~ -t ~ u4 ~ < ~ /dev/urandom } % execute
   { \endlinechar=-1 } % ignore endline
   \l_tmpa_tl % store in
  \tl_set:Nx #1 { \fp_eval:n { \l_tmpa_tl / (2^32) } } % normalize
 }

\NewDocumentCommand{\settorandombit}{m}
 {% #1 = macro to be set
  \sys_get_shell:nnN
   { od ~ -vAn ~ -N1 ~ -t ~ u4 ~ < ~ /dev/urandom } % execute
   { \endlinechar=-1 } % ignore endline
   \l_tmpa_tl % store in
  \tl_set:Nx #1 { \int_compare:nNnTF { \l_tmpa_tl } > {127} { 1 } { 0 } }

 }

\ExplSyntaxOff

\begin{document}

\settorandomnumber\pgfmathresult \pgfmathresult

\settorandomnumber\pgfmathresult \pgfmathresult

\settorandomnumber\pgfmathresult \pgfmathresult

\settorandomnumber\pgfmathresult \pgfmathresult

\settorandombit\pgfmathresult \pgfmathresult

\settorandombit\pgfmathresult \pgfmathresult

\settorandombit\pgfmathresult \pgfmathresult

\settorandombit\pgfmathresult \pgfmathresult

\end{document}