#include <stdio.h>
#include <stdlib.h>
#include <openssl/rsa.h>
#include <openssl/bn.h>
#include <openssl/rand.h>
#include <openssl/err.h>


/* You need a file in your home directory called .rnd
   that is filled with random garbage in order for
   this to work!
*/

int main(int argc, char** argv) {
  RSA* rsa;
  int bitlength = 1024;
  int e = 3;
  unsigned int temp;
  unsigned char buf[1024];

  if(argc < 2) {
    printf("Usage: %s bitlength [public_exponent]\n",argv[0]);
    exit(0);
  }

  /* Initialize the random number generator */

  if(RAND_load_file(RAND_file_name(buf,1024), -1)<1024) {
    printf("Random number generator initialization failed.\n");
    printf("*      You need a file in your home directory called .rnd\n");
    printf("*      that is filled with atleast 1024 bits of randomness\n");
    printf("*      in order for this to work!\n");
    exit(0);

  }

  bitlength = atoi(argv[1]);

  if(argc == 3)
    e = atoi(argv[2]);

  printf("Generating a %d bit key pair (e = %d)... ", bitlength, e); 
  fflush(stdout);

  /* Generate a 1024 bit key with public exponent 3 */
  rsa = RSA_generate_key(bitlength, e, NULL, NULL);
  if (!rsa) {
    printf("RSA key generation failed.\n");
    ERR_load_crypto_strings();
    printf("%s\n",ERR_error_string(ERR_get_error(),NULL));
    exit(0);
  }

  printf(" complete.\n\n");

  printf("Public key parameters:\n");
  printf("  Modulus length: %X\n", BN_num_bytes(rsa->n));
  printf("  Modulus value:\n");
  BN_print_fp(stdout, rsa->n);
  printf("\n  Exponent length: %X\n", BN_num_bytes(rsa->e));
  printf("  Exponent value: ");
  BN_print_fp(stdout, rsa->e);

  printf("\n\nPrivate key parameters:\n");
  printf("  q prime length: %X\n", BN_num_bytes(rsa->q));
  printf("  q prime value:\n");
  BN_print_fp(stdout, rsa->q);
  printf("\n  p prime length: %X\n", BN_num_bytes(rsa->p));
  printf("  p prime value:\n");
  BN_print_fp(stdout, rsa->p);
  printf("\n  1/q mod(p) length: %X\n", BN_num_bytes(rsa->iqmp));
  printf("  1/q mod(p) value:\n");
  BN_print_fp(stdout, rsa->iqmp);
  printf("\n  Ksec mod(q-1) length: %X\n", BN_num_bytes(rsa->dmq1));
  printf("  Ksec mod(q-1) value:\n");
  BN_print_fp(stdout, rsa->dmq1);
  printf("\n  Ksec mod(p-1) length: %X\n", BN_num_bytes(rsa->dmp1));
  printf("  Ksec mod(p-1) value:\n");
  BN_print_fp(stdout, rsa->dmp1);
  printf("\n");
  RSA_free(rsa);

  RAND_write_file(RAND_file_name(buf,1024));
}