F L Bauer says in his Springer-Verlag book regarding a holocryptic running key from any offset of sqrt(2), sqrt(5), and sqrt(17) arbitrary digit expansions are vulnerable, anyone know why? The only thing I can possibly imagine related, is 19yo Gauss's famous Euclidean constructable proof of the 17-gon, and the pentagon may also be constructed. Something in early Galois, abstract algebra, may be applied to recognizing digit expansions of certain algebraic irrationals?