secure_random
NAME
secure_random() - return a pseudo-random number, this should be
unpredictable, but maybe slightly slow.
SYNOPSIS
int secure_random( int n );
DESCRIPTION
Return a cryptographically secure random number from the range [0 .. (n -1)] (inclusive).
On Linux & OSX, this function explicitly use randomness from /dev/urandom,
on windows it is implementation defined.