mp_result find_strong_prime(mp_int seed, FILE *fb)
{
mp_result res;
mpz_t t;
mp_int_init(&t);
for(;;) {
if ((res = find_prime(seed, fb)) != MP_TRUE)
break;
if ((res = mp_int_copy(seed, &t)) != MP_OK)
break;
if ((res = mp_int_mul_pow2(&t, 1, &t)) != MP_OK ||
(res = mp_int_add_value(&t, 1, &t)) != MP_OK)
break;
if ((res = mp_int_is_prime(&t)) == MP_TRUE) {
if (fb != NULL)
fputc('!', fb);
res = mp_int_copy(&t, seed);
break;
}
else if (res != MP_FALSE)
break;
if (fb != NULL)
fputc('x', fb);
if ((res = mp_int_add_value(seed, 2, seed)) != MP_OK)
break;
}
mp_int_clear(&t);
return res;
}
/* Find the first apparent prime in ascending order from z */
mp_result mp_int_find_prime(mp_int z)
{
mp_result res;
if(mp_int_is_even(z) && ((res = mp_int_add_value(z, 1, z)) != MP_OK))
return res;
while((res = mp_int_is_prime(z)) == MP_FALSE) {
if((res = mp_int_add_value(z, 2, z)) != MP_OK)
break;
}
return res;
}
int test_add(testspec_t *t, FILE *ofp)
{
mp_int in[3], out[1];
int v;
mp_result res, expect;
if(!parse_int_values(t, in, out, &expect))
return imath_errno = MP_BADARG, 0;
if(strcmp(t->code, "addv") == 0) {
if((res = mp_int_to_int(in[1], &v)) != MP_OK)
return imath_errno = res, 0;
if((res = mp_int_add_value(in[0], v, in[2])) != expect)
return imath_errno = res, 0;
} else {
if((res = mp_int_add(in[0], in[1], in[2])) != expect)
return imath_errno = res, 0;
}
if(expect == MP_OK && mp_int_compare(in[2], out[0]) != 0) {
mp_int_to_string(in[2], 10, g_output, OUTPUT_LIMIT);
return imath_errno = OTHER_ERROR, 0;
}
return 1;
}
mp_result find_prime(mp_int seed, FILE *fb)
{
mp_result res;
int count = 0;
if(mp_int_is_even(seed))
if((res = mp_int_add_value(seed, 1, seed)) != MP_OK)
return res;
while((res = mp_int_is_prime(seed)) == MP_FALSE) {
++count;
if(fb != NULL && (count % 50) == 0)
fputc('.', fb);
if((res = mp_int_add_value(seed, 2, seed)) != MP_OK)
return res;
}
if(res == MP_TRUE && fb != NULL)
fputc('+', fb);
return res;
}
int main(int argc, char *argv[])
{
int opt, modbits;
FILE *ofp = stdout;
char *expt = NULL;
rsa_key the_key;
mp_result res;
/* Process command-line arguments */
while((opt = getopt(argc, argv, "e:")) != EOF) {
switch(opt) {
case 'e':
expt = optarg;
break;
default:
fprintf(stderr, "Usage: rsakey [-e <expt>] <modbits> [<outfile>]\n");
return 1;
}
}
if(optind >= argc) {
fprintf(stderr, "Error: You must specify the number of modulus bits.\n");
fprintf(stderr, "Usage: rsakey [-e <expt>] <modbits> [<outfile>]\n");
return 1;
}
modbits = (int) strtol(argv[optind++], NULL, 0);
if(modbits < CHAR_BIT) {
fprintf(stderr, "Error: Invalid value for number of modulus bits.\n");
return 1;
}
if(modbits % 2 == 1)
++modbits;
/* Check if output file is specified */
if(optind < argc) {
if((ofp = fopen(argv[optind], "wt")) == NULL) {
fprintf(stderr, "Error: Unable to open output file for writing.\n"
" - Filename: %s\n"
" - Error: %s\n", argv[optind], strerror(errno));
return 1;
}
}
if((res = rsa_key_init(&the_key)) != MP_OK) {
fprintf(stderr, "Error initializing RSA key structure:\n"
" - %s (%d)\n", mp_error_string(res), res);
return 1;
}
/* If specified, try to load the key exponent */
if(expt != NULL) {
if((res = mp_int_read_string(&(the_key.e), 10, expt)) != MP_OK) {
fprintf(stderr, "Error: Invalid value for encryption exponent.\n"
" - %s (%d)\n", mp_error_string(res), res);
goto EXIT;
}
}
if((res = mp_int_randomize(&(the_key.p), (modbits / 2))) != MP_OK) {
fprintf(stderr, "Error: Unable to randomize first prime.\n"
" - %s (%d)\n", mp_error_string(res), res);
goto EXIT;
}
fprintf(stderr, "p: ");
find_prime(&(the_key.p), stderr);
if((res = mp_int_randomize(&(the_key.q), (modbits / 2))) != MP_OK) {
fprintf(stderr, "Error: Unable to randomize second prime.\n"
" - %s (%d)\n", mp_error_string(res), res);
goto EXIT;
}
fprintf(stderr, "\nq: ");
find_prime(&(the_key.q), stderr);
fputc('\n', stderr);
/* Temporarily, the key's "n" field will be (p - 1) * (q - 1) for
purposes of computing the decryption exponent.
*/
mp_int_mul(&(the_key.p), &(the_key.q), &(the_key.n));
mp_int_sub(&(the_key.n), &(the_key.p), &(the_key.n));
mp_int_sub(&(the_key.n), &(the_key.q), &(the_key.n));
mp_int_add_value(&(the_key.n), 1, &(the_key.n));
if(expt == NULL &&
(res = mp_int_randomize(&(the_key.e), (modbits / 2))) != MP_OK) {
fprintf(stderr, "Error: Unable to randomize encryption exponent.\n"
" - %s (%d)\n", mp_error_string(res), res);
goto EXIT;
}
while((res = mp_int_invmod(&(the_key.e), &(the_key.n),
&(the_key.d))) != MP_OK) {
if(expt != NULL) {
fprintf(stderr, "Error: Unable to compute decryption exponent.\n"
" - %s (%d)\n", mp_error_string(res), res);
goto EXIT;
}
if((res = mp_int_randomize(&(the_key.e), (modbits / 2))) != MP_OK) {
fprintf(stderr, "Error: Unable to re-randomize encryption exponent.\n"
" - %s (%d)\n", mp_error_string(res), res);
goto EXIT;
}
}
/* Recompute the real modulus, now that exponents are done. */
mp_int_mul(&(the_key.p), &(the_key.q), &(the_key.n));
/* Write completed key to the specified output file */
rsa_key_write(&the_key, ofp);
EXIT:
fclose(ofp);
rsa_key_clear(&the_key);
return 0;
}
