A Lightweight Privacy Protection User Authentication and Key Agreement Scheme Tailored for the Internet of Things Environment: LightPriAuth

Algorithm 5

role sensor (Ui, Sj, GW: agent,

     Kxj: symmetric_key,

     H: hash_func,

     P: text,

     SND_SG,RCV_SG: channel(dy))

played_by Sj

def=

 local State: nat,

 T2,K2,A,B,SK,M3,M4,M5,SIDj :text

 const shared_key:protocol_id

 init State:= 4

 transition

  1. State = 4  ⋀ RCV_SG(A’

              .H(A’.SIDj’.Kxj.T2’)

              .T2’

              )=|>

   State’:= 3   ⋀ K2’:= new()

           ⋀ B:= exp(P,K2’)

           ⋀ SK’:= H(exp(A’,K2))

           ⋀ M4’:= H(B.SK.A’)

           ⋀ M5’:= H(Kxj.H(A’.SIDj’.Kxj.T2’).M4’.B)

           ⋀ SND_SG(B.M4’.M5’)

           ⋀ witness(Ui,Sj,shared_key,SK’)

           ⋀ request(Ui,Sj,shared_key,SK’)

 end role