“…In recent years, more and more researchers proposed an authentication and key-agreement scheme for WSNs environment [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Most of them proposed schemes for general purposes [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 17 , 24 ] and few of them proposed schemes for specific purposes [ 16 , 18 , 19 , 20 , 25 , 26 ]. For example, in 2009, Pecori and Veltri [ 25 ] proposed a new alternative key agreement protocol for setting up multimedia sessions between user agents (UAs) without requiring any pre-shared key or trust relationship or PKI, and it has been implemented and integrated in a publicly available VoIP UA.…”