util

src/crypto_VDF/utils.py

@@ -0,0 +1,34 @@
+def exp_modular(a: int, exponent: int, n: int) -> int:
+    """
+    Modular exponentiation
+
+    :param a: number to exponentiate
+    :param exponent: exponent
+    :param n: modulus
+    :return: a^exponent (mod n)
+    """
+    exp = int_2_base(exponent, 2)
+    c = a
+    for i in range(1, len(exp)):
+        c = c * c % n
+        if exp[i] == 1:
+            c = c * a % n
+    return c
+
+
+def int_2_base(a: int, base: int) -> list:
+    """
+    Convert integer to base "base"
+
+    :param a: integer to convert to big number form in base "base"
+    :param base: base into which to convert integer "a"
+    :return: bin number form in base "base" corresponding to "a"
+    """
+    x = a
+    reminders = []
+    while x != 0:
+        q = x // base
+        r = x % base
+        x = q
+        reminders.append(r)
+    return reminders[::-1]