Ubiquitous networks provide roaming service for mobile nodes enabling them to use the services extended by their home networks in a foreign network. A mutual authentication scheme between the roamed mobile node and the foreign network is needed to be performed through the home network. Various authentication schemes have been developed for such networks, but most of them failed to achieve security in parallel to computational efficiency. Recently, Shin et al. and Wen et al. separately proposed two efficient authentication schemes for roaming service in ubiquitous networks. Both argued their schemes to satisfy all the security requirements for such systems. However, in this paper, we show that Shin et al.'s scheme is susceptible to: (i) user traceability; (ii) user impersonation; (iii) service provider impersonation attacks; and (iv) session key disclosure. Furthermore, we show that Wen et al.'s scheme is also insecure against: (i) session key disclosure; and (ii) known session key attacks. To conquer the security problems, we propose an improved authentication scheme with anonymity for consumer roaming in ubiquitous networks. The proposed scheme not only improved the security but also retained a lower computational cost as compared with existing schemes. We prove the security of proposed scheme in random oracle model.
of 20Step 1: MN ! FA: M 1 D ¹M V 1 ; M V 2 ; M V 3 º MN inputs his identity ID MN and password P W MN . MN then computes h.ID M jjh.P W MN // and checks if the result and A MN stored in his mobile device are of 20 4 Mobile node chooses its identity ID MN , password P W MN , and a random number d . Further, MN computes f D h.ID MN kP W MN kd /. Finally, MN sends ID MN and f to the HA by using some secure channel. HA computes K MN D h.ID MN jjx/˚f using secret x. Further, HA pledges a counter ct r MN D 0 for MN and forms a record .ID MN ; ct r MN / in his database. HA then engraves the smart card (SC MN ) with K MN , ct r MN , h.:/, and n. HA issues the smart card (SC MN ) to MN. After obtaining the smart card (SC MN ), MN computes f D h.ID MN˚P W MN˚d / and writes f on SC MN . Finally, the SC MN contains ¹ct r MN ; K MN ; f ; n; d , h.:/º.
Login and authentication phaseThe procedure for login and authentication is outlined in Figure 3; the same is illustrated as follows: (1) MN ! FA W M 1 . MN inserts his smart card (SC MN ) in the reader and enters his identity ID MN and password P W MN . SC MN computes f 0 D h.ID MN˚P W MN˚d / and then verifies whether f 0 D f or not. If f 0 ¤ f , the login phase terminates immediately. Otherwise, SC MN computes K MN D K MN˚h .ID MN kP W MN kd /. Then SC MN generates random n MN and computes ct r MN D ct r MN C 1 and V 1 D .ID MN jj K MN jjn MN jjct r MN jjID FA / 2 modn. Finally, MN sends the M 1 D .V 1 ; ct r MN ; ID HA / to FA.Figure 3. Wen et al.'s scheme [38].
Proposition 5 (Secure key establishment)The improved scheme provides secure key establishment.
ProofAfter completion of the protocol, the MN, FA, and HA will establish a common session key SK FA D SK MN ...