True Random (short c-source)

I have written a short random number generator which appears to produce
reasonable random numbers even in DOS, at the heart of the code is the
short function fGetRand, the amount of entropy derived from this
function varies from >1 to >>6 depending on system load, I haven't
made any effort to whiten it at all. I am not making any claims about
its usefulness. I am only trying to demonstrate the ease at which
good random number may be obtained. Any comments and analysis will be
mostly welcome, the source is hereby placed in the public domain:

I have used WATCOM10 to compile and test under DOS/WIN95, where
clock is running at 18hz. I have also tested on IRIX with impressive
results.

--- START ----
#include <time.h>
#include <stdio.h>

int   fGetRand (void);

main (void) {
   long vCount;
   FILE *out;
   int byte;
   int tick;

   out=fopen("random.bin","wb");
   if(out==NULL) {
      printf("cant write to file random.bin\n");
      exit(1);
   }

   for(vCount=1;vCount<=512;vCount++) {
      tick=fGetRand()&0x01;
      byte=byte+byte+tick;
      if((vCount & 0x7)==0) fputc((char)byte,out);
      fputc((char)tick,out);
   }

   fclose(out);
}


int   fGetRand (void) {
   int count;
   clock_t tick;

   tick=clock();
   while(tick==clock()) count++;

   return (count);
}
----- END -----

PGP encrypted mail preferred, finger for key.
The above views are ONLY endorsed by BoggleMind Inc. (not to be confused
with MindBoggle Ltd.)

What you are doing, basically, is using the processor execution time
loops to measure jitter in the return of the value of clock(). I don't
know how clock() works but I would venture to guess that the jitter in
more predictable than you think.

.pm

Frank Andrew Stevenson writes:
> I have written a short random number generator which appears to produce
> reasonable random numbers even in DOS, at the heart of the code is the
> short function fGetRand, the amount of entropy derived from this
> function varies from >1 to >>6 depending on system load, I haven't
> made any effort to whiten it at all. I am not making any claims about
> its usefulness. I am only trying to demonstrate the ease at which
> good random number may be obtained. Any comments and analysis will be
> mostly welcome, the source is hereby placed in the public domain:
> 
> I have used WATCOM10 to compile and test under DOS/WIN95, where
> clock is running at 18hz. I have also tested on IRIX with impressive
> results.
> 
> --- START ----
> #include <time.h>
> #include <stdio.h>
> 
> int   fGetRand (void);
> 
> main (void) {
>    long vCount;
>    FILE *out;
>    int byte;
>    int tick;
> 
>    out=fopen("random.bin","wb");
>    if(out==NULL) {
>       printf("cant write to file random.bin\n");
>       exit(1);
>    }
> 
>    for(vCount=1;vCount<=512;vCount++) {
>       tick=fGetRand()&0x01;
>       byte=byte+byte+tick;
>       if((vCount & 0x7)==0) fputc((char)byte,out);
>       fputc((char)tick,out);
>    }
> 
>    fclose(out);
> }
> 
> 
> int   fGetRand (void) {
>    int count;
>    clock_t tick;
> 
>    tick=clock();
>    while(tick==clock()) count++;
> 
>    return (count);
> }
> ----- END -----
> 
> PGP encrypted mail preferred, finger for key.
> The above views are ONLY endorsed by BoggleMind Inc. (not to be confused
> with MindBoggle Ltd.)
> 
> 
>

Frank Andrew Stevenson wrote:

| I have written a short random number generator which appears to produce
| reasonable random numbers even in DOS, at the heart of the code is the
| short function fGetRand, the amount of entropy derived from this

	What tests have you done on the output that causes you to say
the random numbers are 'reasonable'?

Adam

-- 
"It is seldom that liberty of any kind is lost all at once."
					               -Hume