Table 4.

Comparison of E-SAP functionality with related schemes.

Functionalities	[34]	[42]	[43]	[46]	Proposed E-SAP
Strong user authentication	No	Yes	No	Yes	Yes
Mutual authentication between Ui and Sn	Yes	No	Yes	No	Yes
Session key establishment	No	No	No	No	Yes
Secure password change	NA	No	Yes	Yes	Yes
Message confidentiality	No	No	No	No	Yes
Protection to replay message	Yes	Yes	Yes	Yes	Yes
Secure against GW secret key guessing attack	Yes	No	No	No	Yes
Secure against user masquerading attack	Yes	No	No	No	Yes
Secure against gateway masquerading attack	No	No	No	No	Yes
Secure against Information-leakage attack	No	No	No	No	Yes
Protocol formal verification	No	No	No	No	Yes

NA: Not applicable.