opensslPRandEx.c

/**
   @file      opensslPRandEx.c
   @author    Mitch Richling <http://www.mitchr.me/>
   @Copyright Copyright 1999 by Mitch Richling.  All rights reserved.
   @brief     OpenSSL random number generator example.@EOL
   @Keywords  openssl random number generator example
   @Std       C89

              OpenSSL is a cryptographic toolkit containing many
              useful things including a excellent, cryptographic
              random number generator and a reasonably good
              pseudo-random number generator.

              The two functions at the center of random number
              generation are RAND_pseudo_bytes and RAND_bytes.  They
              both generate multiple bytes of random information in
              one call.  RAND_bytes & RAND_pseudo_bytes are
              essentially interchangeable if all that is needed is a
              non-secure random number.

              RAND_pseudo_bytes() has been in OpenSSL since 0.9.5.
              RAND_bytes() has always been in OpenSSL, and got a
              return value in v0.9.5

*/

#include <openssl/rand.h>
#include <stdlib.h>             /* Standard Lib    ISOC  */
#include <stdio.h>              /* I/O lib         ISOC  */

int main(int argc, char *argv[]);

int main(int argc, char *argv[]) {

  int i, randInt;
  int randInts[10];

 /* One way to get random integers -- full range */
 if( !(RAND_pseudo_bytes((unsigned char *)randInts, sizeof(randInts)))) {
   printf("ERROR: call to RAND_pseudo_bytes() failed\n");
   exit(1);
 }

 /* Print out our random integers.  Note we abs() them to 
    fold into non-negative integers.  One might also wish 
    to exclude 0 from the stream for obvious reasons */
 for(i=1; i<10; i++) {
   randInt = abs(randInts[i]);
   printf("Random Integer: %d\n", randInt);
 }

 return 0;
}