// rsacpp.cpp: определяет точку входа для консольного приложения.
//

#include "stdafx.h"
#include <iostream>
#include <time.h>
using namespace std;

// 405 простых чиселс
unsigned long long arr[405] = { 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997, 1009, 1013, 1019, 1021, 1031, 1033, 1039, 1049, 1051, 1061, 1063, 1069, 1087, 1091, 1093, 1097, 1103, 1109, 1117, 1123, 1129, 1151, 1153, 1163, 1171, 1181, 1187, 1193, 1201, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1277, 1279, 1283, 1289, 1291, 1297, 1301, 1303, 1307, 1319, 1321, 1327, 1361, 1367, 1373, 1381, 1399, 1409, 1423, 1427, 1429, 1433, 1439, 1447, 1451, 1453, 1459, 1471, 1481, 1483, 1487, 1489, 1493, 1499, 1511, 1523, 1531, 1543, 1549, 1553, 1559, 1567, 1571, 1579, 1583, 1597, 1601, 1607, 1609, 1613, 1619, 1621, 1627, 1637, 1657, 1663, 1667, 1669, 1693, 1697, 1699, 1709, 1721, 1723, 1733, 1741, 1747, 1753, 1759, 1777, 1783, 1787, 1789, 1801, 1811, 1823, 1831, 1847, 1861, 1867, 1871, 1873, 1877, 1879, 1889, 1901, 1907, 1913, 1931, 1933, 1949, 1951, 1973, 1979, 1987, 1993, 1997, 1999, 2003, 2011, 2017, 2027, 2029, 2039, 2053, 2063, 2069, 2081, 2083, 2087, 2089, 2099, 2111, 2113, 2129, 2131, 2137, 2141, 2143, 2153, 2161, 2179, 2203, 2207, 2213, 2221, 2237, 2239, 2243, 2251, 2267, 2269, 2273, 2281, 2287, 2293, 2297, 2309, 2311, 2333, 2339, 2341, 2347, 2351, 2357, 2371, 2377, 2381, 2383, 2389, 2393, 2399, 2411, 2417, 2423, 2437, 2441, 2447, 2459, 2467, 2473, 2477, 2503, 2521, 2531, 2539, 2543, 2549, 2551, 2557, 2579, 2591, 2593, 2609, 2617, 2621, 2633, 2647, 2657, 2659, 2663, 2671, 2677, 2683, 2687, 2689, 2693, 2699, 2707, 2711, 2713, 2719, 2729, 2731, 2741, 2749, 2753, 2767, 2777, 2789, 2791, 2797, 2801, 2803, 2819, 2833, 2837, 2843, 2851, 2857, 2861, 2879, 2887, 2897, 2903, 2909, 2917, 2927, 2939, 2953, 2957, 2963, 2969, 2971, 2999, 3001, 3011, 3019, 3023, 3037, 3041, 3049, 3061, 3067, 3079, 3083, 3089, 3109, 3119, 3121, 3137, 3163, 3167, 3169, 3181, 3187, 3191, 3203, 3209, 3217, 3221, 3229, 3251, 3253, 3257, 3259, 3271, 3299, 3301, 3307, 3313, 3319, 3323, 3329, 3331, 3343, 3347, 3359, 3361, 3371, 3373, 3389, 3391, 3407, 3413, 3433, 3449, 3457, 3461, 3463, 3467, 3469, 3491, 3499, 3511, 3517, 3527, 3529, 3533, 3539, 3541, 3547, 3557, 3559, 3571 };

unsigned long long gcd(unsigned long long a, unsigned long long b)
{
    unsigned long long t = b;
    b = a % b;
    if (b == 0)
        return t;
    else
        return gcd(t, b);
}

int random(int min, int max)
{
    return min + (rand() % (max - min + 1));
}

unsigned long long getOpenExp(unsigned long long M)
{
    unsigned long long E = 0;
    while (true)
    {
        E = arr[random(0, 405)];
        if (gcd(E, M) == 1)
            return E;
    }
}

unsigned long long modInverse(unsigned long long a, unsigned long long b)
{
    unsigned long long i = b, v = 0, d = 1;
    while (a > 0)
    {
        unsigned long long t = i / a, x = a;
        a = i % x;
        i = x;
        x = d;
        d = v - t * x;
        v = x;
    }
    v %= b;
    if (v < 0) v = (v + b) % b;
    return v;
}

unsigned long long powmod(unsigned long long d, unsigned long long p, unsigned long long m)
{
    unsigned long long b;
    for (b = 1; p;)
        if (p & 1) {
            p--;
            b = b*d%m;
        }
        else {
            p >>= 1;
            unsigned long long tmp = d%m;
            d = (tmp * tmp) % m;
        }
        return b;
}

int main()
{
    srand(time(NULL));
    unsigned long long P, Q, N, M, E, D, A, ENCODE, DECODE;
    int type = 0;

    cout << "P = ";
    cin >> P;

    cout << "Q = ";
    cin >> Q;

    cout << "\n";

    N = P * Q;
    M = (P - 1) * (Q - 1);
    E = getOpenExp(M);
    D = modInverse(E, M);

    cout << "Number for encode: ";
    cin >> A;
    ENCODE = powmod(A, E, N);
    DECODE = powmod(ENCODE, D, N);


    cout<< "N = " << N << "\n"
        << "M = " << M << "\n"
        << "E = " << E << "\n"
        << "D = " << D << "\n\n"
        << "ENCODE = " << ENCODE << "\n"
        << "DECODE = " << DECODE;

    // останавливаем программу, чтобы не закрылась
    system("pause > nil");

    return 0;
}