Cfrtjryk

This is my first attempt to implement an crypto algorithm.

I am using C and gmp.h to interact with big number.

Here is my code, you can run in with -lgmp parameter:

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <math.h>

#include <sys/types.h>

#include "gmp.h"







void generatePrimes(mpz_t* p, mpz_t* q);

void computeNandF(mpz_t* q, mpz_t* p, mpz_t *phi, mpz_t* n);

void generateE(mpz_t* phi, mpz_t* e);

void enc(mpz_t* e, mpz_t* n, mpz_t* d, mpz_t* c, char);

void dec(mpz_t* m, mpz_t* c, mpz_t* d, mpz_t* n);

void makeKeys(mpz_t n, mpz_t e, mpz_t d, mpz_t p, mpz_t q);

void encrFile(mpz_t e, mpz_t n, mpz_t d, mpz_t c);



gmp_randstate_t stat;



int main() {





 mpz_t p, q, phi, e, n, d, c, dc;

 char msg[40] = "welcome to cryptoworld";

 int *mes;

 int len = strlen(msg);

 mpz_init(p);

 mpz_init(q);

 mpz_init(phi);

 mpz_init(e);

 mpz_init(n);

 mpz_init(d);

 mpz_init(c);

 mpz_init(dc);



 // RSA algorithm

 generatePrimes(&p, &q);

 computeNandF(&q, &p, &phi, &n);

 generateE(&phi, &e);

 // extended Euclidean

 mpz_invert(d, e, phi);

 printf("d = ");

 mpz_out_str(stdout, 10, d);

 printf("n------------------------------------------------------------------------------------------n");





 enc(&e, &n, &d, &c, msg);



 dec(&dc, &c, &d, &n);



 printf("n------------------------------------------------------------------------------------------n");

 printf("encrypt message  = ");

 mpz_out_str(stdout, 10, c);

 printf("n");

 printf("n------------------------------------------------------------------------------------------n");

 printf("message as int after decr  = ");

 mpz_out_str(stdout, 10, dc);

 printf("n");





 mpz_export(mes, (size_t*) malloc(sizeof (size_t)), 1, sizeof (mes[0]), 0, 0, dc);

 char r[40];

 printf("message as string after decr  = ");

 for (int i = 0; i < len; i++) {

     r[i] = (char) mes[i];

     printf("%c", r[i]);

 }

 printf("n");



 encrFile(e, n, d, c);



 mpz_clear(p);

 mpz_clear(q);

 mpz_clear(phi);

 mpz_clear(n);

 mpz_clear(e);

 mpz_clear(c);

 mpz_clear(d);

 mpz_clear(dc);

 return 0;

}



void generatePrimes(mpz_t* p, mpz_t* q) {



 int primetest;

 long sd = 0;

 mpz_t seed;

 gmp_randinit(stat, GMP_RAND_ALG_LC, 120);

 mpz_init(seed);

 srand((unsigned) getpid());

 sd = rand();

 mpz_set_ui(seed, sd);

 gmp_randseed(stat, seed);





 mpz_urandomb(*p, stat, 512);

 primetest = mpz_probab_prime_p(*p, 10);

 if (primetest != 0) {

    printf("p is primen");

 } else {

    //printf("p wasnt prime,choose next primen");

    mpz_nextprime(*p, *p);

 }



 mpz_urandomb(*q, stat, 512);

 primetest = mpz_probab_prime_p(*q, 10);

 if (primetest != 0) {

    // printf("q is primen");

 } else {

    // printf("p wasnt prime,choose next primen");

    mpz_nextprime(*q, *q);

 }





 printf("p and q generated!!n");

 printf("p = ");

 mpz_out_str(stdout, 10, *p);

 printf("q = ");

 mpz_out_str(stdout, 10, *q);

 printf("n------------------------------------------------------------------------------------------n");

 mpz_clear(seed);

 return;

}



void computeNandF(mpz_t* q, mpz_t* p, mpz_t *phi, mpz_t* n) {



 mpz_t temp1, temp2;

 mpz_init(temp1);

 mpz_init(temp2);

 //n=p*q

 mpz_mul(*n, *q, *p);

 mpz_sub_ui(temp1, *q, 1); //temp1=q-1

 mpz_sub_ui(temp2, *p, 1); //temp2=p-1

 //φ=(p-1)(q-1)

 mpz_mul(*phi, temp1, temp2);

 printf("phi and n generated!!n");

 printf(" n= ");

 mpz_out_str(stdout, 10, *n);

 printf("phi = ");

 mpz_out_str(stdout, 10, *phi);

 printf("n------------------------------------------------------------------------------------------n");

}



void generateE(mpz_t* phi, mpz_t* e) {



 mpz_t temp, seed;

 mpz_init(seed);

 mpz_init(temp);

 long sd = 0;

 gmp_randinit(stat, GMP_RAND_ALG_LC, 120);

 srand((unsigned) getpid());

 sd = rand();

 mpz_set_ui(seed, sd);

 gmp_randseed(stat, seed);



 do {

    mpz_urandomm(*e, stat, *phi + 1);

    mpz_gcd(temp, *phi, *e); //temp=gcd(e,φ)

 } while (mpz_cmp_ui(temp, 1) != 0); //while gcd!=1

 printf("e generated n e = ");

 mpz_out_str(stdout, 10, *e);

 printf("n------------------------------------------------------------------------------------------n");



 }



void enc(mpz_t* e, mpz_t* n, mpz_t* d, mpz_t* c, char msg) {



 int r[40];

 for (int i = 0; i < strlen(msg); i++) {

    r[i] = (int) msg[i];

 }



 int *m = r;

 mpz_t M;

 mpz_init(M);

 mpz_import(M, strlen(msg), 1, sizeof (m[0]), 0, 0, m);

 printf("message as int before encryption  = ");

 mpz_out_str(stdout, 10, M);

 printf("n");



 mpz_powm(*c, M, *e, *n);



}



void dec(mpz_t* m, mpz_t* c, mpz_t* d, mpz_t* n) {



  mpz_powm(*m, *c, *d, *n);



}



void encrFile(mpz_t e, mpz_t n, mpz_t d, mpz_t c) {



  char text[80];

  FILE *file;

  file = fopen("text.txt", "r");

  int i = 0;

  if (file) {

     while ((x = getc(file)) != EOF) {

         i++;

         putchar(x);

         text[i] = (char) x;

     }



    int r[40];

    for (int i = 0; i < strlen(text); i++) {

        r[i] = (int) text[i];

    }



    int *m = r;

    mpz_t M;

    mpz_init(M);

    mpz_import(M, strlen(text), 1, sizeof (m[0]), 0, 0, m);

    printf("message as int before encryption  = ");

    mpz_out_str(stdout, 10, M);

    printf("n");



    mpz_powm(c, M, e, n);

    printf("encrypt txt  = ");

    mpz_out_str(stdout, 10, c);

    printf("n");



    fclose(file);

    file = fopen("text.txt", "w");



    mpz_out_raw(file, c);

    fclose(file);



  }



}

Any comments and improvements in my implementation will be appreciate.