Untitled

size_t modpow(size_t x, size_t power, size_t mod)
{
        /* Only powers of two need to be multiplied together the get the result.
         *
         * Here we use the Euclidean algorithm to retreive those powers,
         * multiplying them together and reducing by the modulus at each iteration
         * to "avoid" overflow (ha!). */
        size_t result = 1;

        while (power > 0) {
                if ((power % 2) == 0) {
                        result = (result * x) % mod;
                }

                power /= 2;
                x = (x * x) % mod;
        }

        return result;
}