149 lines
2.7 KiB
C
149 lines
2.7 KiB
C
#include "rsa.h"
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#include "rand.h"
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#include <stdbool.h>
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#include <stdint.h>
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uint64_t gcd(uint64_t a, uint64_t b) {
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while (b != 0) {
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uint64_t temp = b;
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b = a % b;
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a = temp;
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}
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return a;
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}
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int extended_euclid(int a, int b, int *x, int *y) {
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if (b == 0) {
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*x = 1;
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*y = 0;
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return a;
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}
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int x1, y1;
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int gcd = extended_euclid(b, a % b, &x1, &y1);
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// Update x and y using results from recursive call
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*x = y1;
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*y = x1 - (a / b) * y1;
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return gcd;
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}
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int totient(int n) {
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int result = n;
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// Check for prime factors
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for (int p = 2; p * p <= n; p++) {
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if (n % p == 0) {
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// If p is a prime factor of n, remove all occurrences of p
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while (n % p == 0) {
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n /= p;
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}
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result -= result / p;
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}
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}
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// If n is still greater than 1, then it's a prime factor itself
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if (n > 1) {
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result -= result / n;
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}
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return result;
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}
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uint64_t modexp(uint64_t a, uint64_t b, uint64_t m) {
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uint64_t result = 1;
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a = a % m; // In case a is greater than m
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while (b > 0) {
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// If b is odd, multiply a with result
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if (b % 2 == 1)
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result = (result * a) % m;
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// b must be even now
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b = b >> 1; // b = b // 2
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a = (a * a) % m; // Change a to a^2
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}
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return result;
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}
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uint64_t gen_prime(uint64_t min, uint64_t max) {
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uint64_t cand = 0;
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while (!miller_rabin(cand, 5)) cand = prand_range(min, max);
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return cand;
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}
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bool is_prime(int n) {
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if (n < 2)
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return false;
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for (int i = 2; i < n / 2 + 1; i++) {
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if (n % i == 0)
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return false;
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}
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return true;
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}
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bool miller_rabin(uint64_t n, uint64_t k) {
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if (n < 2)
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return false;
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uint64_t d = n - 1;
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uint64_t s = 0;
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while (d % 2 == 0) {
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d /= 2;
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s++;
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}
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for (uint64_t i = 0; i < k; i++) {
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uint64_t a = prand_range(2, n - 2);
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uint64_t x = modexp(a, d, n);
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if (x == 1 || x == n - 1)
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continue;
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for (uint64_t r = 1; r < s; r++) {
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x = modexp(x, 2, n);
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if (x == n - 1)
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break;
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}
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if (x != n - 1)
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return false; // Not prime
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}
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return true; // Likely prime
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}
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int mod_inverse(int a, int m) {
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int m0 = m;
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int y = 0, x = 1;
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if (m == 1)
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return 0;
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while (a > 1) {
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// q is quotient
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int q = a / m;
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int t = m;
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// m is remainder now
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m = a % m;
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a = t;
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t = y;
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// Update x and y
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y = x - q * y;
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x = t;
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}
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// Make x positive
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if (x < 0)
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x += m0;
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return x;
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}
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