Hierarchical access control is an important and traditional problem in
information security. In 2001, Wu et.al. proposed an elegant solution for
hierarchical access control by the secure-filter. Jeng and Wang presented an
improvement of Wu et. al.'s method by the ECC cryptosystem. However,
secure-filter method is insecure in dynaminc access control. Lie, Hsu and
Tripathy, Paul pointed out some secure leaks on the secure-filter and presented
some improvements to eliminate these secure flaws. In this paper, we revise the
secure-filter in Jeng-Wang method and propose another secure solutions in
hierarchical access control problem. CA is a super security class (user) in our
proposed method and the secure-filter of $u_i$ in our solutions is a polynomial
of degree $n_i+1$ in $\mathbb{Z}_p^*$,
$f_i(x)=(x-h_i)(x-a_1)...(x-a_{n_i})+L_{l_i}(K_i)$. Although the degree of our
secure-filter is larger than others solutions, our solution is secure and
efficient in dynamics access control.