migration

semester-4/ОС/lb-2/src/library/rsa.cpp

@@ -0,0 +1,78 @@
+#include "rsa.h"
+
+__int128_t mul_mod(__int128_t a, __int128_t b, __int128_t mod) {
+  __int128_t res = 0;
+  a %= mod;
+
+  while (b > 0) {
+    if (b & 1)
+      res = (res + a) % mod;
+
+    a = (a << 1) % mod;
+    b >>= 1;
+  }
+
+  return res;
+}
+
+__int128_t pow_mod(__int128_t base, __int128_t exp, __int128_t mod) {
+  __int128_t res = 1;
+  base %= mod;
+
+  while (exp > 0) {
+    if (exp & 1)
+      res = mul_mod(res, base, mod);
+
+    base = mul_mod(base, base, mod);
+    exp >>= 1;
+  }
+
+  return res;
+}
+
+__int128_t mod_inverse(__int128_t e, __int128_t phi) {
+  __int128_t a = e, b = phi;
+  __int128_t x = 1, y = 0;
+  __int128_t x1 = 0, y1 = 1;
+  __int128_t q, temp;
+
+  while (b != 0) {
+    q = a / b;
+
+    temp = a % b;
+    a = b;
+    b = temp;
+
+    temp = x - q * x1;
+    x = x1;
+    x1 = temp;
+
+    temp = y - q * y1;
+    y = y1;
+    y1 = temp;
+  }
+
+  if (x < 0)
+    x += phi;
+
+  return x;
+}
+
+rsa_Pair rsa_gen_pair(__int128_t p, __int128_t q, __int128_t e) {
+  rsa_Pair pair;
+  pair.e = e;
+  pair.n = p * q;
+
+  __int128_t phi = (p - 1) * (q - 1);
+  pair.d = mod_inverse(e, phi);
+
+  return pair;
+}
+
+__int128_t rsa_encrypt(__int128_t data, __int128_t e, __int128_t n) {
+  return pow_mod(data, e, n);
+}
+
+__int128_t rsa_decrypt(__int128_t data, __int128_t d, __int128_t n) {
+  return pow_mod(data, d, n);
+}