Login Phase i When wanting to access the information of the cloud server Sm, Ui provides ID∗, P ∗ and B∗ to a card reader (CR). Then, CR calculates A∗ = P ∗ ⊕ h (B∗), C∗ = h (ID∗ ǁ A∗) and checks whether C∗ =?Ci or not. If C∗ = Ci , CR pro- duces a random number Ni and current timestamp TSi to compute the following operations: bi = Ωi ⊕ Ai, PIDi = h (IDi ǁ bi), Di = Ei ⊕ Ai, Oi = IDi ⊕ D, Gi = x (XXx ǁ XXXx ǁ Xx ǁ XXx ǁ Xx), Xx = ∆i ⊕ Ni and Zi = SIDm ⊕ h (Di ǁ Ni). After that, CR submits the login message (Gi, Fi, Zi, Oi, PIDi, TSi) to the cloud server Sm over an public channel.
Login Phase. If Ui wants to get information from the private cloud server Sm, Ui inserts the smart cart into the IoT-enabled device and provides ID∗,P ∗ and and B∗. The device i i i computes A∗ = P ∗ ⊕ h (B∗) and C∗ = h (ID∗ ǁ A∗). Then, it verifies C∗ =?Ci. If C∗ = Ci, the device authenticates the real Ui; otherwise, it rejects this login of Ui. Next, the device generates an at least 128 bits random number Ni and executes the follow operations: b = Ωi ⊕ Ai PIDi = h (IDi ǁ b) Di = Ei ⊕ Ai Gi = h (PIDi ǁ SIDm ǁ Ni ǁ TSi ǁ Di) Fi = Di ⊕ Ni Zi = SIDm ⊕ h (Di ǁ Ni) where TSi is the current timestamp of the device, SIDm is the private server Sm’s identity. After that, the device transmits (Gi, Fi, Zi, PIDi, TSi) to Sm via a public channel.
Login Phase. When A wants to communicate toB, A performs this login phase with TS. The details of this phase are as follows.
Login Phase. At this stage, user logs in and assigns a key to the cloud server. As shown in Fig. 4 and Fig. 5, the user and the cloud server performs this process as bellow. Ci Join Phase
Login Phase. Step 1: Ui inputs IDi∗ and pwi∗ into SCi. ? Step 2: SCi computes RNr∗ = h(pwi∗ ) ⊕ XPWi, HPWi∗ = h(pwi∗ ||RNr∗ ), XS∗i = Ci ⊕ h(IDS||HPWi∗ ), Bi∗ = h(HPWi∗ ⊕ XS∗i . Then, SCi verifies Bi∗ = Bi. If it is valid, SCi computes ki = h(XS∗i ||Ti), DIDi = h(HPWi∗ ||XS∗i ) ⊕ ki, MUi ,G = h(Ai||XS∗i ||Ti), where Ti is the timestamp. Step 3: Ui sends {XXXx, MUi ,G , Xx, TIDi} to GWN.
Login Phase. A user Ui inserts his smart card into a card reader to login on to server S and submits his identity IDi and password Pi. Smart card verifies authenticity of the user Ui and sends user Ui’s verification information to the destination server S.
Login Phase. The userUi keys his identity IDi , password PWi and the server identity SIDj in order to login the service provider Sj.
Login Phase. When Ui logins the system, he/she can perform the next steps. • Ui inserts his/her smart card into a card reader and enters the identity IDi, password PWi. The smart card SC computes bt = B ⊕ IDi ⊕ PWi, Ct = C2 ⊕ h(bt ǁPWi) ⊕ h(IDi), Ct = h(Ct ), and phase, authentication phase and password change phase. 1 t 3 1 The notations used in this article are described in Table 1. Table 1: Notation compares C3 with C3 stored in the smart card. Only if the equation holds, XX performs the following steps. • SC generates a random number v and computes V = gv mod n, h(xǁy) = c4 ⊕ h(bǁPWi), CIDi = h(IDi)⊕h(V ǁh(xǁy)), M1 = h(CIDiǁV ||C1). Then, Xx sends login request message {CIDi, V, M1} to Si.
Login Phase. When Ui logins the system, he/she can perform the next steps. C 3 ǁ ǁ ⊕ ⊕ ǁ • Ui inserts his/her smart card into a card reader and enters the identity IDi, password PWi. The smart card SC computes b = B ⊕ IDi ⊕ PWi, RPWi = h(b PWi), C1 = C2 RPWi, d = C4 h(C1 RPWi), t = h(C1 d), and compares Ct with C3 stored in the smart card. Only if the equation holds, SC per- forms the following steps. • SC generates a random number v and computes V = gv mod n, D = gd mod n, h(xǁyǁD) = C5 ⊕ h(C1ǁIDi), CIDi = IDi ⊕ h(V ǁh(xǁyǁD)), F1 = RPWi ⊕h(C1ǁIDi), F2 = C4 ⊕h(V ǁC1)⊕h(xǁyǁD), M1 = h(IDiǁRPWiǁV ǁC1ǁd). Then, Xx sends login
