On Mon, 7 Mar 2005, Vineet Joglekar wrote:
> Hi all,
>
> Can someone please tell me where can I find and which random/pseudo-random
> number generator can I use inside the linux kernel? (2.4.28)
I Don't know how this is done for actual use in the kernel itself - So I
cannot answer that particular question and... I may be way out of my
league here, but why not use /dev/urandom ? Just to illustrate! I have
included an example of that below... If it lives up to your idea of
`cryptographicly secure' - ... ?
> I found out 1 function get_random_bytes() in linux/drivers/char/random.c
> but thats not what I want.
>
> I want a function where I will be supplying a seed to that function as an
> input,
> and will get a random number back. If same seed is used, same number
> should be generated again.
>
> Can anybody please help me with that?
>
> Thanks and regards,
>
> Vineet.
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
unsigned time_seed(void);
int get_rand_val(int low, int high);
int main(void) {
int i = 0;
srand((time_seed()));
for(i = 0; i < 10; i++)
printf("%d\n", get_rand_val(1, 10));
return 0;
}
int get_rand_val(int low, int high) {
int k = 0;
double d = 0;
d = (double)rand() / ((double)RAND_MAX + 1);
k = (int)(d * (high - low + 1));
return(low + k);
}
unsigned time_seed(void) {
int retval = 0;
int fd = 0;
if(open("/dev/urandom", O_RDONLY) == -1) {
retval = (((int)time(NULL)) & ((1 << 30) - 1)) + getpid();
} else {
read(fd, &retval, 4);
/* positive values only */
retval = abs(retval) + getpid();
close(fd);
}
return retval;
}
Cheers, J.
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