c++ implementation

cpp/main.cpp

@@ -0,0 +1,187 @@
+#include <iostream>
+#include <random>
+#include <ctime>
+#include <gmpxx.h>
+using namespace std;
+
+#define MAX_TEXT_LENGHT 2048
+
+mpz_class z_powm(const mpz_class base, mpz_class exponent, const mpz_class modulo);
+mpz_class z_gcd(mpz_class a, mpz_class b);
+mpz_class z_multiplicate_inverse(mpz_class e, mpz_class phi);
+bool z_isPrime(mpz_class number);
+
+void z_generate_keypair(const mpz_class prime_one, const mpz_class prime_two, mpz_class* result);
+
+void z_encrypt(const mpz_class* z_key, const char* plaintext, const int lenght, mpz_class* result);
+void z_decrypt(const mpz_class* z_key, const mpz_class* cipher, const int lenght, char* result);
+
+int main()
+{
+    srand(time(NULL));
+
+    mpz_class input_prime_one, input_prime_two, key_pair[3], encrypted_text[MAX_TEXT_LENGHT];
+    char input_plaintext[MAX_TEXT_LENGHT], decrypted_text[MAX_TEXT_LENGHT];
+
+    cout << "Hello world!" << endl << "Note: Accents will not work because of cin limitations." << endl << endl;
+
+    cout << "Enter a prime number: ";
+    cin >> input_prime_one;
+
+    if (!z_isPrime(input_prime_one)){ //Optional
+        cout << endl << "This is not a prime number !" << endl << endl << "Exit 1" << endl;
+        return 1;
+    }
+
+    cout << endl << "Enter another prime number: ";
+    cin >> input_prime_two;
+
+    if (input_prime_one == input_prime_two){ //Optional
+        cout << endl << "The numbers you entered are identical !" << endl << endl << "Exit 1" << endl;
+        return 1;
+    }
+
+    if (!z_isPrime(input_prime_two)){ //Optional
+        cout << endl << "This is not a prime number !" << endl << endl << "Exit 1" << endl;
+        return 1;
+    }
+
+    z_generate_keypair(input_prime_one, input_prime_two, key_pair);
+
+    cout << endl <<  "Common key: " << key_pair[0]
+         << endl <<  "Public key: " << key_pair[1]
+         << endl << "Private key: " << key_pair[2];
+
+    cout << endl << "Enter a text to encrypt: ";
+
+    cin.ignore();
+    cin.getline(input_plaintext, MAX_TEXT_LENGHT);
+
+    int text_lenght = strlen(input_plaintext); //needed for the decryption because there's no clean way to obtain an array's lenght
+
+    cout << endl << "Text lenght: " << text_lenght;
+
+    z_encrypt(key_pair, input_plaintext, text_lenght,encrypted_text);
+
+    cout << endl << "Encrypted text: "; //note that the output is not representative since the value is stored in an array
+    for (int i=0; i<text_lenght; ++i) // plus the encryption is made on characters 1 by 1
+        cout << encrypted_text[i];
+
+    z_decrypt(key_pair, encrypted_text, text_lenght, decrypted_text);
+
+    cout << endl << "Decrpted text: ";
+    for (int i=0; i<text_lenght; ++i)
+        cout << decrypted_text[i];
+    cout << endl << endl << "Exit 0" << endl;
+    return 0;
+}
+
+
+mpz_class z_powm(const mpz_class base, mpz_class exponent, const mpz_class modulo)
+{
+    mpz_class x=1, y=base;
+    while (exponent){
+        if (exponent % 2 == 1)
+            x = (x*y) % modulo;
+        y = (y*y) % modulo;
+        exponent /=2;
+    }
+
+    return x%modulo;
+}
+
+mpz_class z_gcd(mpz_class a, mpz_class b)
+{
+    mpz_class c;
+    while (b!=0)
+    {
+        c = b;
+        b = a%b;
+        a = c;
+    }
+    return a;
+}
+
+mpz_class z_multiplicate_inverse(mpz_class e, mpz_class phi)
+{
+    mpz_class d = 0, x1 = 0, x2 = 1, y1 = 1, temp_phi = phi, temp1, temp2, x, y;
+
+    while (e >0){
+        temp1 = temp_phi/e;
+        temp2 = temp_phi - temp1*e;
+        temp_phi = e;
+        e = temp2;
+
+        x = x2 - temp1*x1;
+        y = d - temp1*y1;
+
+        x2 = x1;
+        x1 = x;
+        d = y1;
+        y1 = y;
+    }
+
+    if (temp_phi == 1) return d+phi;
+
+    return -1; //failsafe
+}
+
+void z_generate_keypair(const mpz_class prime_one, const mpz_class prime_two, mpz_class* result) //since return can't return arrays you need a pointer to an exteernal array...
+{
+    //check for primarity ?
+
+    mpz_class p_times_q = prime_one * prime_two;
+
+    mpz_class phi = (prime_one - 1) * (prime_two -1);
+
+    mpz_class e = rand() % phi + 1;
+
+    mpz_class g = z_gcd(e, phi);
+
+    while (g != 1) {
+        e = rand() % phi + 1;
+        g = z_gcd(e, phi);
+    }
+
+    mpz_class d = z_multiplicate_inverse(e, phi);
+
+    //0 is common key(modulo), 1 is public key, 3 is private key
+
+    result[0] = p_times_q;
+    result[1] = e;
+    result[2] = d;
+
+    return;
+}
+
+void z_encrypt(const mpz_class* z_key, const char* plaintext, const int lenght, mpz_class* result) //same here
+{
+    for (int i=0; i<lenght; ++i){
+        result[i] = z_powm(mpz_class(plaintext[i]), z_key[1], z_key[0]);
+    }
+    return;
+}
+
+void z_decrypt(const mpz_class* z_key, const mpz_class* cipher, const int lenght, char* result) //same
+{
+    for (int i=0; i<lenght; ++i){
+        result[i] = z_powm(cipher[i], z_key[2], z_key[0]).get_ui();
+    }
+    return;
+}
+
+bool z_isPrime(mpz_class number)
+{
+    if(number<2)
+        return false;
+    if(number==2)
+        return true;
+    if(number%2==0)
+        return false;
+    for(int i=3;i<=sqrt(number);i += 2)
+    {
+        if(number%i==0)
+            return false;
+    }
+    return true;
+}