This function sets the random number seed for the
srand( time() ^ ($$ + ($$ << 15)) );
Of course, you'd need something much more random than that for serious cryptographic purposes, since it's easy to guess the current time. Checksumming the compressed output of one or more rapidly changing operating system status programs is the usual method. For example:
srand (time ^ $$ ^ unpack "%32L*", `ps axww | gzip`);
Do not call srand multiple times in your program unless you know exactly what you're doing and why you're doing it. The point of the function is to "seed" the rand function so that rand can produce a different sequence each time you run your program. Just do it once at the top of your program, or you won't get random numbers out of rand !