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

Algorithm 6

role gateway (Ui, Sj, GW: agent,

      Kdi,Kei, Kxj, Xgwn: symmetric_key,

      H: hash_func,

      SND_UG,RCV_UG,SND_SG,RCV_SG: channel(dy))

played_by GW

def=

 local State: nat,

 T1,T2,A,B,IDi,SIDj,M2,M3,M4,M6,M7,Ki,Keinew,K3: text

 const sc_user_id,sc_sensor_id:protocol_id

 init State: = 2

 transition

 1. State = 2  ⋀ RCV_UG(A’.

            xor(H(Ki’.Xgwn),(IDi’.SIDj’.H(A’.IDi’.SIDj’.Kdi.T1’))).

            Ki’.

            T1’

            )=|>

 State’:= 3  ⋀ T2’: = new()

         ⋀ M3’:= H(A’.SIDj’.Kxj.T2’)

         ⋀ SND_SG(A’.M3’.T2’)

         ⋀ secret(IDi,sc_user_id,{Ui,GW})

         ⋀ secret(SIDj,sc_sensor_id,{Ui,GW})

 2. State = 5  ⋀ RCV_SG(B

             .M4’

             .H(Kxj.M3.M4’.B)

             )=|>

 State’:=6  ⋀ K3’:= new()

             ⋀ Keinew’:= H(K3’.Xgwn)

             ⋀ M7’:= H(Kei.K3’.Kdi.T1.M4’)

             ⋀ M6’:= xor((Keinew’.K3’.M7’),Kei)

             ⋀ SND_UG(B.M6’)

end role