In this paper, we analyze a one-way hash chain based authentication scheme proposed by Haddad and Krishnan. The authentication scheme has been introduced for improving handover performance in Fast Mobile IPv6 (FMIPv6), but as we argue in this paper the authentication scheme is vulnerable to redirect and DoS attacks. We present strengths and weaknesses of the authentication scheme. In addition, a possible extension to NEtwork MObility (NEMO) is suggested. Keywords-Authentication; Hash; FMIPv6; NEMO.