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Imbus 2025-05-03 17:54:58 +02:00
parent 66b499bc06
commit 117adf9da1
1 changed files with 14 additions and 26 deletions
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40
rsa.c
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@ -7,20 +7,16 @@ u64 gcd(u64 a, u64 b) { return extended_euclid(a, b, NULL, NULL); }
u64 extended_euclid(u64 a, u64 b, u64 *x, u64 *y) { u64 extended_euclid(u64 a, u64 b, u64 *x, u64 *y) {
if (b == 0) { if (b == 0) {
if (x) if (x) *x = 1;
*x = 1; if (y) *y = 0;
if (y)
*y = 0;
return a; return a;
} }
u64 x1, y1; u64 x1, y1;
u64 gcd = extended_euclid(b, a % b, &x1, &y1); u64 gcd = extended_euclid(b, a % b, &x1, &y1);
if (x) if (x) *x = y1;
*x = y1; if (y) *y = x1 - (a / b) * y1;
if (y)
*y = x1 - (a / b) * y1;
return gcd; return gcd;
} }
@ -56,8 +52,8 @@ u64 mulmod(u64 a, u64 b, u64 m) {
if (b & 1) { if (b & 1) {
result = (result + a) % m; result = (result + a) % m;
} }
a = (a * 2) % m; // Double a, keep it within the modulus a = (a * 2) % m; // Double a, keep it within the modulus
b >>= 1; // Right shift b (divide by 2) b >>= 1; // Right shift b (divide by 2)
} }
return result; return result;
@ -86,20 +82,17 @@ u64 gen_prime(u64 min, u64 max) {
} }
bool is_prime(u64 n) { bool is_prime(u64 n) {
if (n < 2) if (n < 2) return false;
return false;
for (int i = 2; i < n / 2 + 1; i++) { for (int i = 2; i < n / 2 + 1; i++) {
if (n % i == 0) if (n % i == 0) return false;
return false;
} }
return true; return true;
} }
bool miller_rabin(u64 n, u64 k) { bool miller_rabin(u64 n, u64 k) {
if (n < 2) if (n < 2) return false;
return false;
u64 d = n - 1; u64 d = n - 1;
u64 s = 0; u64 s = 0;
@ -113,17 +106,14 @@ bool miller_rabin(u64 n, u64 k) {
u64 a = prand_range(2, n - 2); u64 a = prand_range(2, n - 2);
u64 x = modexp(a, d, n); u64 x = modexp(a, d, n);
if (x == 1 || x == n - 1) if (x == 1 || x == n - 1) continue;
continue;
for (u64 r = 1; r < s; r++) { for (u64 r = 1; r < s; r++) {
x = modexp(x, 2, n); x = modexp(x, 2, n);
if (x == n - 1) if (x == n - 1) break;
break;
} }
if (x != n - 1) if (x != n - 1) return false; // Not prime
return false; // Not prime
} }
return true; // Likely prime return true; // Likely prime
@ -134,8 +124,7 @@ u64 mod_inverse(u64 a, u64 m) {
u64 y = 0, x = 1; u64 y = 0, x = 1;
// Modular inverse does not exist when m is 1 // Modular inverse does not exist when m is 1
if (m == 1) if (m == 1) return 0;
return 0;
while (a > 1) { while (a > 1) {
// q is quotient // q is quotient
@ -153,8 +142,7 @@ u64 mod_inverse(u64 a, u64 m) {
} }
// Make x positive // Make x positive
if (x < 0) if (x < 0) x += m0;
x += m0;
return x; return x;
} }