Table 2.

Security comparison

scheme	[28]	[24]	[25]	[35]	[30]	Our
Mutual authentication and key agreement	√	√	√	√	√	√
User anonymity	√	√	√	×	√	√
User un-traceability	√	×	×	√	√	√
Perfect forward secrecy	√	√	√	√	×	√
User friendliness	×	×	√	√	√	√
Resist stolen-verifier attack	×	×	√	√	×	√
Resist off-line password guessing attack	×	√	×	×	√	√
Resist privileged insider attack	√	√	√	√	√	√
Resist the user impersonation attack	√	√	√	√	√	√
Resist the replay attack	√	×	×	√	×	√
Resist man-in-the-middle attack	√	√	√	√	√	√
Resist the denial of service attack	×	√	×	×	√	√
Resist ephemeral secret leakage attack	√	×	×	×	√	√
Resist smart card loss attack	√	√	×	√	√	√