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

Algorithm 4

role user (Ui, Sj, GW: agent,

    Kdi,Kei: symmetric_key,

    H: hash_func

    P: text,

    SND_US,RCV_US: channel (dy))

played_by Ui

def=

 local State: nat,

 T1,K1,A,M1,M2,Ki,B,K3,K2,IDi,SIDj,M4,M6,M7,SK,Keinew: text

 const shared_key,sc_user_id,sc_sensor_id:protocol_id

 init State:= 0

 transition

   1. State = 0   RCV_US(start)=|>

   State’: = 2   ⋀ T1’:= new()

         ⋀ K1’:= new()

         ⋀ A’:= exp(P,K1’)

         ⋀ M2’:= H(A’.IDi.SIDj.Kdi.T1’)

         ⋀ M1’:= xor(Kei,(IDi.SIDj. H(A’.IDi.SIDj.Kdi.T1’)))

         ⋀ SND_UG(A’.M1’.Ki.T1’)

   2. State = 7  ⋀ RCV_UG(B

              .xor((Keinew’.K3’.H(Kei.K3’.Kdi.T1.M4’)),Kei)

              )=|>

   State’:= 8  ⋀ Kei’:= Keinew’

         ⋀ Ki’:= K3’

         ⋀ SK’:= H(exp(B,K1))

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

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

  end role