Add a comment for exponentiation

synedrion/src/tools/secret.rs

@@ -376,6 +376,10 @@ impl<T: Zeroize> Secret<T> {
         V: Integer + crypto_bigint::Bounded + Encoding + ConditionallySelectable,
     {
         // TODO: do we need to implement our own windowed exponentiation to hide the secret?
+        // The exponent will be put in a stack array when it's decomposed with a small radix
+        // for windowed exponentiation. So if it's secret, it's going to leave traces on the stack.
+        // With the multiplication, for example, there's less danger since Uints implement *Assign traits which we use,
+        // so theoretically anything secret will be overwritten.
         Secret::init_with(|| self.expose_secret().pow_signed_vartime(exponent))
     }
 }