79 lines
1.3 KiB
C
79 lines
1.3 KiB
C
#include "rsa.h"
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uint16_t get_random_bytes(int fd) {
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uint16_t ret;
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if (read(fd, &ret, sizeof(uint16_t)) == -1) {
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exit(1);
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}
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return ret;
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}
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// n pow e mod m
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uint64_t pow_mod(uint64_t n, uint64_t e, uint64_t m) {
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uint64_t y = 1;
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while (e > 1) {
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if (e & 1) {
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y = (y * n) % m;
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}
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n = (n * n) % m;
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e = e >> 1;
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}
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return (n * y) % m;
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}
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bool is_prime(uint16_t n, size_t k_max, int fd) {
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uint16_t a = get_random_bytes(fd);
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// a &= 0xFFFF;
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uint16_t d = n - 1;
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uint16_t s = 0;
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while ((d & 1) == 0) {
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s++;
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d = d >> 1;
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}
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for (size_t k = 0; k < k_max; k++) {
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a = 0;
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while (a < 2 || a > (n - 2)) {
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a = get_random_bytes(fd);
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//a &= 0xFFFF;
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}
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uint16_t x = pow_mod(a, d, n);
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uint16_t y;
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for (uint16_t i = 0; i < s; i++) {
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y = pow_mod(x, 2, n);
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if (y == 1 && x != 1 && x != n - 1)
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return false;
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x = y;
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}
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if (y != 1) {
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return false;
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}
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}
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return true;
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}
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uint16_t generate_prime_fd(int fd) {
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uint16_t n = get_random_bytes(fd);
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n |= 1 << 15;
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n |= 1;
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//n &= 0xFFFF;
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while (/*n % 3 == 0 ||*/ !is_prime(n, 16, fd)) {
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n = get_random_bytes(fd);
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n |= 1 << 15;
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n |= 1;
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//n &= 0xFFFF;
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}
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return n;
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}
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uint16_t generate_prime() {
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int fd = open("/dev/urandom", O_RDONLY);
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uint16_t n = generate_prime_fd(fd);
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close(fd);
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return n;
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}
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