// Generate a numbits-bit probable prime using the Random-Search algorithm
void rndsearch(int numbits, int maxitr, FILE* primesfile, FILE* rndfile) {
bool found_prime = false;
int count = 1;
int num_bytes = ceil(numbits/8.0);
BIGNUM* num_orig = BN_new();
char* num_trimmed = (char*)calloc(1, num_bytes);
// Iterate through potential numbers in RandomFile
while(!found_prime) {
printf("RANDOM-SEARCH: iteration %d\n", count);
// Generate random odd numbit-long integer
RndOddNum(numbits, num_orig, rndfile);
num_trimmed = BN_bn2dec(num_orig);
// Test with trial division
printf(" n = %s\n", num_trimmed);
printf(" ");
if(trialdiv(num_trimmed, primesfile)) {
// Passed trial division, check Miller-Rabin
if(millerrabin(num_trimmed, maxitr, primesfile, " ")) {
found_prime = true;
}
}
count++;
}
BN_free(num_orig);
free(num_trimmed);
// PSEUDO-CODE
// - Generate a random numbit-bit number
// - Read ceil(numbit/8) bytes from the random file
// - Set bits 0 and numbit-1 to 1
// - Set bits numbit to ceil(numbit/8)*8 to 0
// - Run the Trial Division test
// - If it passes, run the Miller-Rabin test
// - If it passes that too, return that prime number
// - If it fails either test, return to the beginning and try a new number
}
/*
* rndsearch function to generate numbits-bit probable prime
* @param: k numbits, maxitr, FILE pointer to primesfile, FILE pointer to rndfile
* @output: Print out rndsearch process and generate a probable prime
*/
void rndsearch(int k, int maxitr, FILE *fp, FILE *fp_rndfile)
{
int byte = 0;
int x_byte = ceil_func((double)k/8, (int)k/8);
char *temp = malloc(x_byte); //read in x_byte from rndfile
int itr_count = 1;
while((byte = fread(temp, 1, x_byte, fp_rndfile)) > 0)
{
BIGNUM *bn_n = RndOddNum(k, temp, x_byte);
if(bn_n == NULL)
{
free(temp);
return; //ERROR has happened in RndOddNum() function call
}
else
{
//Print itr
fprintf(stdout, "RANDOM-SEARCH: iteration %d\n", itr_count);
itr_count += 1;
fprintf(stdout, " n = %s\n", BN_bn2dec(bn_n));
//Use trial division function to check if n passes trial division test
int trialdiv_returnCode = trialdiv(bn_n, fp, 2);
//reset fp pointer to beginning of primesfile for next time use
rewind(fp);
if(trialdiv_returnCode == -1)
{
//error has happened in trialdiv function. Terminate this function
free(temp);
BN_free(bn_n); //free from RndOddNum() function call
return;
}
else if(trialdiv_returnCode == 0)
{
BN_free(bn_n);
continue; //bn_n does not pass trial division test. Continue to generate next number
}
int millerrabin_returnCode = millerrabin(bn_n, maxitr, fp, 2);
//reset fp pointer to beginning of primesfile for next time use
rewind(fp);
if(millerrabin_returnCode == -1)
{
//error has happened in millerrabin function. Terminate this function
free(temp);
BN_free(bn_n); //free from RndOddNum() function call
return;
}
else if(millerrabin_returnCode == 1)
{
free(temp);
BN_free(bn_n); //free from RndOddNum() function call
return; //Prove n to be a prime number. End function
}
else
{
//continue generate the next probable prime
BN_free(bn_n);
}
}
}
//Free in case we have never generated a bn_n that passes both tests
free(temp);
fprintf(stderr, "Run out of bytes in rndfile and we have not successfully generated a prime number\n");
}