Security Analysis and Improvement of an Anonymous Authentication Scheme for Roaming Services

Algorithm 1

Login and key agreement phase of He et al.’s scheme [12].

inputs and

retrieves the timestamp

            checks the freshness of

            retrieves the timestamp

                         checks the freshness of

                     Does yield and ?

                       Does yield ?

                        Does yield ?

                        retrieves the timestamp

            checks the freshness of

checks the freshness of

Does yield , and ?