final touches

helper.c

@@ -2,6 +2,8 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+uint32_t rand32() { return (rand() << 16) | (rand() & 0xFFFF) | 1; }
+
 void print_uint128(unsigned __int128 n) {
     if (n == 0) {
         printf("0\n");
@@ -30,12 +32,14 @@ uint64_t rand64() {
     for (int i = 0; i < 4; i++) {
         r = (r << 16) | (rand() & 0xFFFF);
     }
+
+    // Force the bottom bit to 1, this will make all generated primes odd
+    r = r | 1;
     return r;
 }
 
 // Stitch two 64-bit random numbers into a 128-bit number
 unsigned __int128 generate_stitched_128() {
-    // Make sure to seed rand() in your main function with srand(time(NULL))
     uint64_t top_half = rand64();
     uint64_t bottom_half = rand64();
 
@@ -46,10 +50,9 @@ unsigned __int128 generate_stitched_128() {
 }
 
 unsigned __int128 generate_prime_candidate() {
-    // 1. Get the raw random bytes
     unsigned __int128 candidate = generate_stitched_128();
 
-    // 2. Force the bottom bit to 1 (Ensures it is odd)
+    // Force the bottom bit to 1, this will make all generated primes odd
     candidate = candidate | 1;
 
     // 3. Force the top bit to 1 (Ensures it is a full 128-bit number)

main.c

@@ -59,6 +59,18 @@ bool prime_test(uint64_t n, int a) {
     // S: see above
     // r = {0,... S-1}
 
+    // this should not happen but just in case
+    if (n <= 1) {
+        return false;
+    }
+    if (n == 2) {
+        return true;
+    }
+    if (n % 2 == 0) {
+        return false;
+    }
+    //
+
     uint64_t d = n - 1;
     uint64_t S = 0;
 
@@ -72,8 +84,9 @@ bool prime_test(uint64_t n, int a) {
     // round 1
     // 1: a^d =k 1 mod n
     uint64_t length = 0;
+    // convert exponent to binary to use in quickpow
     uint64_t *d_binary = dec_to_bin(d, &length);
-    uint64_t first_qp_res = quick_pow(d_binary, a, n, length);
+    unsigned __int128 first_qp_res = quick_pow(d_binary, a, n, length);
 
     if (first_qp_res == 1) {
         free(d_binary);
@@ -87,10 +100,8 @@ bool prime_test(uint64_t n, int a) {
             free(d_binary);
             // printf("true\n");
             return true;
-        } else if (first_qp_res < n - 2) {
-            // printf("first_qp_res became smaller then n!!\n");
-            break;
         } else {
+            //^2 with mod n, for each step since the next is the previous's squared
             first_qp_res = (uint64_t)(((unsigned __int128)first_qp_res * first_qp_res) % n);
         }
     }
@@ -101,17 +112,14 @@ bool prime_test(uint64_t n, int a) {
 
 typedef struct {
     int base;
-    uint64_t prime;
+    uint32_t prime;
 } prime_test_t;
 
 void *prime_thread_worker(void *arg) {
     prime_test_t *result_ptr = (prime_test_t *)arg;
 
     do {
-        result_ptr->prime = rand64();
-        // printf("\nGenerating a new prime number (%p). Candidate: ", result_ptr);
-        // printf("%ju", result_ptr->prime);
-        // printf("\n");
+        result_ptr->prime = rand32();
     } while (!prime_test(result_ptr->prime, result_ptr->base));
 
     return NULL;
@@ -123,7 +131,7 @@ typedef struct {
     __int128 y;
 } euklidian_result_t;
 
-euklidian_result_t euklidian_algorigthm_extended(unsigned __int128 a, unsigned __int128 b) {
+euklidian_result_t euklidian_algorigthm_extended(uint64_t a, uint64_t b) {
     __int128 r = a % b, q = a / b, k = 1, xk = 0, yk = 1, next_r;
     __int128 prev_r = b, prev_q, prev_xk = 0, prev_yk = 1, prev_prev_xk = 1, prev_prev_yk = 0;
     euklidian_result_t res = {0, 0, 0};
@@ -138,11 +146,11 @@ euklidian_result_t euklidian_algorigthm_extended(unsigned __int128 a, unsigned _
         prev_r = r;
         r = next_r;
 
-        xk = xk * prev_q + prev_prev_xk;
+        xk = prev_xk * prev_q + prev_prev_xk;
         prev_prev_xk = prev_xk;
         prev_xk = xk;
 
-        yk = yk * prev_q + prev_prev_yk;
+        yk = prev_yk * prev_q + prev_prev_yk;
         prev_prev_yk = prev_yk;
         prev_yk = yk;
     }
@@ -150,17 +158,18 @@ euklidian_result_t euklidian_algorigthm_extended(unsigned __int128 a, unsigned _
     __int128 x = k % 2 == 0 ? prev_xk : -prev_xk;
     __int128 y = k % 2 == 0 ? -prev_yk : prev_yk;
 
-    res.lnko = prev_r;
+    // the reason this can be casted is that two uint64_t-s cant have a lnko which is bigger than a uint64_t
+    res.lnko = (uint64_t)prev_r;
     res.x = x;
     res.y = y;
 
     return res;
 }
 
-unsigned __int128 kinai_maradek_tetel(uint64_t *m, uint64_t d, prime_test_t *p, prime_test_t *q) {
+uint64_t kinai_maradek_tetel(uint64_t *m, uint64_t d, prime_test_t *p, prime_test_t *q) {
     // sum(i: 1,2): Ci * Yi * Mi mod M
     // M: P*Q, Mp: M/P, Mq: M/Q
-    unsigned __int128 M = p->prime * q->prime;
+    uint64_t M = (uint64_t)p->prime * q->prime;
     uint64_t Mp = q->prime;
     uint64_t Mq = p->prime;
 
@@ -180,44 +189,57 @@ unsigned __int128 kinai_maradek_tetel(uint64_t *m, uint64_t d, prime_test_t *p,
     euklidian_result_t y = euklidian_algorigthm_extended(Mp, Mq); // in the struct the x will mean the y1 and y will mean the y2
 
     // if either of them is less a negative number shift them into postive range with with hte modulo
-    y.x %= p->prime;
-    y.x += p->prime;
-    y.y %= q->prime;
-    y.y += q->prime;
+    uint64_t y1_pos;
+    if (y.x < 0) {
+        y1_pos = p->prime - (uint64_t)(-y.x % p->prime);
+    } else {
+        y1_pos = (uint64_t)y.x % p->prime;
+    }
 
-    unsigned __int128 s1 = (c1 * y.x * Mp) % M;
-    unsigned __int128 s2 = (c2 * y.y * Mq) % M;
-    return (s1 + s2) % M;
+    uint64_t y2_pos;
+    if (y.y < 0) {
+        y2_pos = q->prime - (uint64_t)(-y.y % q->prime);
+    } else {
+        y2_pos = (uint64_t)y.y % q->prime;
+    }
+
+    // Apply the modulo between multiplications to prevent 192-bit overflows!
+    uint64_t s1 = (uint64_t)((((unsigned __int128)c1 * y1_pos) % M * Mp) % M);
+    uint64_t s2 = (uint64_t)((((unsigned __int128)c2 * y2_pos) % M * Mq) % M);
+    return (uint64_t)(((unsigned __int128)s1 + s2) % M);
 }
 
-unsigned __int128 rsa_encrypt(uint64_t *m, prime_test_t *p, prime_test_t *q) {
-    unsigned __int128 n = p->prime * q->prime;
-    printf("n: ");
-    print_uint128(n);
-    printf("\n");
+uint64_t rsa_encrypt(uint64_t *m, prime_test_t *p, prime_test_t *q, uint64_t *out_e, uint64_t *out_d) {
+    uint64_t n = (uint64_t)p->prime * q->prime;
+    printf("n: %ju\n", n);
 
-    unsigned __int128 fi_n = (p->prime - 1) * (q->prime - 1);
-    printf("fi_n: ");
-    print_uint128(fi_n);
-    printf("\n");
+    uint64_t fi_n = (uint64_t)(p->prime - 1) * (q->prime - 1);
+    printf("n: %ju\n", fi_n);
 
-    // 2. kulcsgeneralas
-    uint64_t e = 0;
+    // keygen
+    uint64_t e = 65537;
     do {
-        e = rand64();
-    } while (e <= 1 && e >= fi_n && prime_test(e, p->base)); // the p and q base is used everywhere anyways, i wont pass in another arg
+        e = rand32() % fi_n; // should this go back as a condition inside the while loop?
+    } while (e <= 1 || !prime_test(e, p->base)); // the p and q base is used everywhere anyways, i wont pass in another arg
 
+    // calculate the d value, in eae it will be the y value
     euklidian_result_t calc_d = euklidian_algorigthm_extended(fi_n, e);
 
     // if either of them is less a negative number shift them into postive range with with hte modulo
-    calc_d.x %= fi_n;
-    calc_d.y %= fi_n;
+    uint64_t d;
+    if (calc_d.y < 0) {
+        d = fi_n - (uint64_t)(-calc_d.y);
+    } else {
+        d = (uint64_t)calc_d.y;
+    }
 
-    unsigned __int128 d = calc_d.y;
+    *out_e = e;
+    *out_d = d;
 
     uint64_t length = 0;
+    // m^e mod n
     uint64_t *nyenye = dec_to_bin(e, &length);
-    unsigned __int128 c = quick_pow(nyenye, *m, n, length);
+    uint64_t c = quick_pow(nyenye, *m, n, length);
     free(nyenye);
 
     printf("\nc: ");
@@ -226,9 +248,15 @@ unsigned __int128 rsa_encrypt(uint64_t *m, prime_test_t *p, prime_test_t *q) {
 }
 
 int main() {
+    int isSignature = 0;
+    printf("Please input 0 for Rsa encryption or 1 for Rsa signature: ");
+    scanf("%d", &isSignature);
+    printf("\n");
+
     uint64_t m = 0;
-    printf("give input for m: \n");
+    printf("give input for m: ");
     scanf("%ju", &m);
+    printf("\n");
 
     srand(time(NULL));
 
@@ -244,13 +272,51 @@ int main() {
     pthread_join(thread_q, NULL);
     printf("\n");
 
-    rsa_encrypt(&m, &p, &q);
+    printf("p: %u\n", p.prime);
+    printf("q: %u\n", q.prime);
 
-    printf("\nkinai maradek tetel:\n");
-    unsigned __int128 S = kinai_maradek_tetel(&m, 2263, &p, &q);
-    printf("S: ");
-    print_uint128(S);
-    printf("\n");
+    uint64_t e = 0;
+    uint64_t d = 0;
+
+    if (!isSignature) {
+        // rsa encryption
+        uint64_t c = rsa_encrypt(&m, &p, &q, &e, &d);
+        printf("\nkinai maradek tetel:\n");
+        unsigned __int128 S = kinai_maradek_tetel(&c, d, &p, &q);
+        printf("S: ");
+        print_uint128(S);
+        printf("\n");
+    } else if (isSignature == 1) {
+        // rsa signature
+
+        // generate keys
+        rsa_encrypt(&m, &p, &q, &e, &d);
+        printf("\n");
+
+        // c^d -> creates signature
+        uint64_t signature = kinai_maradek_tetel(&m, d, &p, &q);
+        printf("Signature: ");
+        print_uint128(signature);
+
+        // key verifacation
+        // S^e -> verifies the signature
+        uint64_t e_length = 0;
+        uint64_t *e_binary = dec_to_bin(e, &e_length);
+        uint64_t n = (uint64_t)p.prime * q.prime;
+
+        uint64_t verified_message = quick_pow(e_binary, signature, n, e_length);
+        free(e_binary);
+
+        printf("Verified Message: %ju", verified_message);
+
+        if (verified_message == m) {
+            printf("\nSignature correct\n");
+        } else {
+            printf("\nSignature not correct\n");
+        }
+    } else {
+        printf("Why?\n");
+    }
 
     return 0;
 }