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

Algorithm 1

( Role of the user)

let processUser(idi: bitstring, sidj: bitstring, pwi: bitstring) =

 ( registration phase of the user )

  new ri:bitstring;

 let mpi = hash(con(ri,con(idi,pwi))) in

 out(scUser,(idi,mpi));

 in(scUser,(fi:bitstring,li:bitstring,ki:bitstring));

 let (ei:bitstring) = xor(li, mpi) in

  let (di:bitstring) = xor(fi, mpi) in

  ( Real start of the role )

   ( Message 1)

   new k1:exponent;

   let A = exp(g,k1) in

   new T1:bitstring;

   let m2 = hash(con(g2 h(A),con(idi,(con(sidj,con(di,T1)))))) in

   let m1 = xor(ei,con(idi,con(sidj,m2))) in

   out(cug, (A, ki, m1, T1));

   ( Message 4 )

   in(cug, (B:G, M6:bitstring));

   let (tem:bitstring) = xor(M6, ei) in

   let (einew’:bitstring, tem1: bitstring) = Split(tem) in

   let (k3’:bitstring, m7’:bitstring) = Split(tem1) in

   let skiju = hash(g2h(exp (B, k1))) in

   let m4’ = hash(con(g2h(B),con(skiju,g2h(A)))) in

   if (m7’) = hash(con(einew’,con(k3’,con(di,con(T1,m4’))))) then

       event acceptUser(di);

    let li = xor(mpi,einew’) in

    let ki = k3’ in

       event termUser(di).