A little tool to perform RSA key calculations, all the data is requested in base10

gmprsa

#include <gmp.h>
#include <stdio.h>
#include <assert.h>

/// gcc -o gmprsa gmprsa.c -g -lgmp && ./gmprsa
int main(){

  char inputStr[1024];

  mpz_t p,q,e,n,r,p_,q_,d;

  int flag;

  printf ("Enter p: ");
  scanf("%1023s" , inputStr);
  mpz_init(p);
  mpz_set_ui(p,0);
  flag = mpz_set_str(p, inputStr, 10);
  assert (flag == 0); 
  printf ("p = ");
  mpz_out_str(stdout, 10, p);
  printf ("\n");

  printf ("Enter q: ");
  scanf("%1023s" , inputStr); 
  mpz_init(q);
  mpz_set_ui(q,0);
  flag = mpz_set_str(q, inputStr, 10);
  assert (flag == 0); 
  printf ("q = ");
  mpz_out_str(stdout, 10, q);
  printf ("\n");

  printf ("Enter e: ");
  scanf("%1023s" , inputStr); 
  mpz_init(e);
  mpz_set_ui(e,0);
  flag = mpz_set_str(e, inputStr, 10);
  assert (flag == 0); 
  printf ("e = ");
  mpz_out_str(stdout, 10, e);
  printf ("\n");

  mpz_init(n);
  mpz_mul(n,p,q);
  printf ("n = ");
  mpz_out_str(stdout, 10, n);
  printf ("\n");
  printf ("n (hex) = ");
  mpz_out_str(stdout, 16, n);
  printf ("\n");

  mpz_init(p_);
  mpz_sub_ui(p_, p, 1);
  mpz_init(q_);
  mpz_sub_ui(q_, q, 1);
  mpz_init(r);
  mpz_mul(r,p_,q_);
  printf ("r = ");
  mpz_out_str(stdout, 10, r);
  printf ("\n");

  mpz_init(d);
  mpz_invert (d, e, r);
  printf ("d = ");
  mpz_out_str(stdout, 10, d);
  printf ("\n");
  printf ("d (hex) = ");
  mpz_out_str(stdout, 16, d);
  printf ("\n");

  mpz_clear(p);
  mpz_clear(q);
  mpz_clear(e);
  mpz_clear(n);
  mpz_clear(r);
  mpz_clear(p_);
  mpz_clear(q_);
  mpz_clear(d);

  // Now you can echo your result hex string and pipe it to xxd -r -p | sha256sum
}