# A Provable Secure Cross-Verification Scheme for IoT Using Public Cloud Computing

Authors: Naveed Khan; Jianbiao Zhang; Jehad Ali; Muhammad Salman Pathan; Shehzad Ashraf Chaudhry
Journal: Security and Communication Networks
 (2022)

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## Abstract

Public cloud computing has become increasingly popular due to the rapid advancements in communication and networking technology. As a result, it is widely used by businesses, corporations, and other organizations to boost the productivity. However, the result generated by millions of network-enabled IoT devices and kept on the public cloud server, as well as the latency in response and safe transmission, are important issues that IoT faces when using the public cloud computing. These concerns and obstacles can only be overcome by designing a robust mutual authentication and secure cross-verification mechanism. Therefore, we have attempted to design a cryptographic protocol based on a simple hash function, xor operations, and the exchange of random numbers. The security of the proposed protocol has formally been verified using the ROR model, ProVerif2.03, and informally using realistic discussion. In contrast, the performance metrics have been analyzed by looking into the security feature, communication, and computation costs. To sum it up, we have compared our proposed security mechanism with the state-of-the-art protocols, and we recommend it to be effectively implemented in the public cloud computing environment.


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## Body

## 1. Introduction

Nowadays, cloud computing offers different services to the Internet enabling devices (IoT) for reducing cost and providing efficiency. These cloud servers are accessible via an Internet connection at any time and from any location. As the world moves toward globalization, IoT-enabled devices’ importance and uses increase daily. IoT enables devices to be deployed and used in different applications and environments such as smart homes, smart cities, industries, Internet of Drones (IoD), space, underwater, and many more environments. IoT devices generate massive amounts of data that can be stored in the cloud servers. IoT is an emerging heterogeneous network industry, and 41 billion IoT devices will be connected to the Internet worldwide. These devices will generate 79 Zettabytes of data annually [1].Different enterprises and individuals use three primary cloud deployment models: private, public, and hybrid. The public cloud is the most commonly used because it is cheaper than private and hybrid cloud deployment models. Cloud servers provide platform as a service, storage as a service, software as a service, and infrastructure as a service to different enterprises and users according to their needs.The public cloud delivers services over a public network. Therefore, it raises security concerns when services are delivered over a public network channel. Thus, secure transmission plays a vital role in outsourcing data by corporations, businesses, government entities, and individuals. However, it also needs to notice the recent increase of cyberattacks on different networks and cloud servers and privacy leakage trying to stop those enterprises and individuals from using the cloud services. Therefore, to tackle these issues and challenges for such massive use of the cloud, it is imperative to authenticate the communicating entities to protect the outsourced data from cybercriminals. However, authentication in IoT-enabled devices is not so easy because of limited resources and energy. Therefore, the authentication process should be efficient and reliable for network and energy constraints devices.


### 1.1. Motivation and Contribution

Recent developments in high-speed Internet, such as 5G and 6G architectures, increase the use of IoT-enabled devices. IoT enables devices to generate gigantic amounts of data annually. However, storing, analyzing, and processing vast amounts of data locally are complex. Therefore, cloud computing offers different services to consumers over the Internet to store and process data on servers with minimal cost. However, security is a big concern while transmitting data to the cloud servers over insecure channels because of cyberattacks. Thus, authenticating the communicating party is very important to transmit data securely. According to our analysis, the scheme [2] has vulnerabilities such as anonymity, untraceability, a man in the middle attacks, server impersonation attacks, and secret key disclosure attacks. Therefore, it motivates us to cryptanalysis the scheme [2] and proposes a secure and efficient scheme. Our contribution is to solve the security flaws in the scheme [2] and propose a more efficient and secure protocol. Further contributions are explained in detail below:(i)
The proposed scheme is efficient and based on symmetric-key cryptography to resist all known potential attacks.(ii)
The security analysis of the proposed scheme has been verified using. (A) ROR model. (B) ProVerif for key secrecy, confidentiality, and reachability.(iii)
The symmetric keys have been exchanged through the Diffie–Hellman method to confirm that no one can forge them.(iv)
The performance analysis of the proposed security mechanism has been made, bearing in mind. (A) computation overheads. (B) Communication overheads.(v)
Upon comparing the proposed scenario with the existing scheme, the proposed scheme is lightweight in terms of communication, computation costs, and efficiency.


### 1.2. System Model

Our system model consists of four entities, as shown in Figure1. IoT devices, users, registration servers, and public cloud computing. The IoT devices generate data send to the public cloud servers over the Internet. The users and IoT devices first need to register with the registration server. Further details are given in the proposed scheme section.Figure 1
System model.


### 1.3. Threat Model

We used the famous DY model [3] and CK model [4] as threat and adversary models in our article, where we consider the action and assume the power of A as follows:(i)
TheA can intercept the exchanged messages transmitted among the participants and replay, listen, and forge messages.(ii)
TheA can be insider or outsider dishonest participants.(iii)
TheA can extract secret values from IoT devices and perform power analysis [5].(iv)
TheA cannot extract secret keys from stored data in IoT devices, users, and servers.(v)
TheA can intercept messages and try to modify, delete, insert, and intentionally temper them.


### 1.4. Paper Organization

The rest of this article is laid out as follows: The literature review is presented in detail in Section2, and the proposed scenario is presented in Section 3. Then, in Sections 4 and 5, we examine the proposed framework’s security, and in Section 6, we conduct a performance analysis. Finally, Section 7 brings the paper to a conclusion.


## 1.1. Motivation and Contribution

Recent developments in high-speed Internet, such as 5G and 6G architectures, increase the use of IoT-enabled devices. IoT enables devices to generate gigantic amounts of data annually. However, storing, analyzing, and processing vast amounts of data locally are complex. Therefore, cloud computing offers different services to consumers over the Internet to store and process data on servers with minimal cost. However, security is a big concern while transmitting data to the cloud servers over insecure channels because of cyberattacks. Thus, authenticating the communicating party is very important to transmit data securely. According to our analysis, the scheme [2] has vulnerabilities such as anonymity, untraceability, a man in the middle attacks, server impersonation attacks, and secret key disclosure attacks. Therefore, it motivates us to cryptanalysis the scheme [2] and proposes a secure and efficient scheme. Our contribution is to solve the security flaws in the scheme [2] and propose a more efficient and secure protocol. Further contributions are explained in detail below:(i)
The proposed scheme is efficient and based on symmetric-key cryptography to resist all known potential attacks.(ii)
The security analysis of the proposed scheme has been verified using. (A) ROR model. (B) ProVerif for key secrecy, confidentiality, and reachability.(iii)
The symmetric keys have been exchanged through the Diffie–Hellman method to confirm that no one can forge them.(iv)
The performance analysis of the proposed security mechanism has been made, bearing in mind. (A) computation overheads. (B) Communication overheads.(v)
Upon comparing the proposed scenario with the existing scheme, the proposed scheme is lightweight in terms of communication, computation costs, and efficiency.


## 1.2. System Model

Our system model consists of four entities, as shown in Figure1. IoT devices, users, registration servers, and public cloud computing. The IoT devices generate data send to the public cloud servers over the Internet. The users and IoT devices first need to register with the registration server. Further details are given in the proposed scheme section.Figure 1
System model.


## 1.3. Threat Model

We used the famous DY model [3] and CK model [4] as threat and adversary models in our article, where we consider the action and assume the power of A as follows:(i)
TheA can intercept the exchanged messages transmitted among the participants and replay, listen, and forge messages.(ii)
TheA can be insider or outsider dishonest participants.(iii)
TheA can extract secret values from IoT devices and perform power analysis [5].(iv)
TheA cannot extract secret keys from stored data in IoT devices, users, and servers.(v)
TheA can intercept messages and try to modify, delete, insert, and intentionally temper them.


## 1.4. Paper Organization

The rest of this article is laid out as follows: The literature review is presented in detail in Section2, and the proposed scenario is presented in Section 3. Then, in Sections 4 and 5, we examine the proposed framework’s security, and in Section 6, we conduct a performance analysis. Finally, Section 7 brings the paper to a conclusion.


## 2. Literature Review

The integration of IoT enables devices in public cloud environments to make communication vulnerable to cybercriminals. Therefore, the biggest challenge is securely communicating over open network channels. Nevertheless, the researchers have proposed authentication schemes to communicate with IoT devices in the cloud server environment securely. However, these schemes have security vulnerabilities and high communication and computation costs. These high computations, communication costs, and vulnerable schemes are discussed below.The author [6] proposed an authentication scheme for heterogeneous devices in wireless sensor networks. However, their scheme suffers from known session key and impersonation attacks and cannot provide perfect forward secrecy. Another scheme is proposed in [7] for wireless sensor networks. Nevertheless, their scheme is also vulnerable to known session keys and perfect forward secrecy. Finally, an ECC-based protocol is proposed in [8]. The protocol fulfils most security requirements except replay attacks and perfect forward secrecy. On the other hand, the protocol proposed in [9] has security vulnerabilities such as known session keys, insecure password change phase, and impersonation attacks.Moreover, the authors [10] proposed a secure scheme in a multi-server environment based on the smartcard. However, their scheme has security flaws such as session key disclosure, spoofing, anonymity, traceability, and impersonation attacks. The author [11] proposed an authentication protocol and identified the security flaws in [12]. The protocol [13] proposed a scheme for smart home environments. However, their scheme grieves from offline password guessing attacks and insider attacks. Another scheme was also proposed for smart home environments in [14]. However, their scheme also has security vulnerabilities such as anonymity and cannot provide untraceability. Nevertheless, the protocols proposed in [15, 16] have significant security flaws. These security flaws are mutual authentication, replay attacks, known session keys, anonymity, untraceability, and impersonation attacks.The protocol proposed by [17] suffers from secret key guessing attacks. Therefore, the user and server can easily be compromised. The protocols [18, 19] suffer from session key attacks and secret key guessing attacks, and server and user can be compromised. At the same time, the scheme [14] is also vulnerable to impersonation attacks. The protocol [20] is based on the ECC, but the scheme has security vulnerabilities such as offline password guessing attacks, impersonation attacks, and anonymity issues. Finally, the scheme [21] has serious security vulnerabilities. The scheme [21] suffers from offline password guessing attacks, session key disclosure attacks, anonymity, perfect forward secrecy, impersonation attacks, desynchronization, and man-in-the-middle attacks. The author [22] proposed an ECC-based scheme for IoT devices in wireless sensor networks. According to the author [22], the protocol proposed in [23] is vulnerable to impersonation and password guessing attacks and unable to provide perfect forward secrecy.Furthermore, the scheme [24] suffers from offline password guessing, impersonation, and perfect forward secrecy. The scheme proposed in [25] is based on ECC, but the scheme grieves from impersonation attacks, offline password guessing, man-in-the-middle, and session key disclosure attacks. Finally, the author proposed a scheme for a client-server environment in [26]. However, the scheme cannot resist impersonation, man-in-the-middle, password guessing, perfect forward secrecy, and insider attacks. Nevertheless, the scheme [27] suffers from offline password guessing attacks and anonymity, while the scheme [28] suffers from offline password guessing attacks. A multi-server cloud server authentication scheme based on biometrics has been proposed [29]. However, the scheme suffers from anonymity and man-in-the-middle attacks. The protocol in [30] is designed for a multi-server environment using biometrics. However, the scheme suffers from a known session temporary attack. Finally, a three-factor authentication scheme for a multi-server environment based on ECC is proposed in [31]. However, the scheme has significant security flaws such as impersonation, insider, and known session key temporary attacks and cannot provide perfect secrecy. The scheme [32] suffers from impersonation attacks and known session temporary attacks. The protocol in [33] suffers from DoS attacks and session key attacks, while the scheme [34] cannot resist offline password guessing attacks.Moreover, the scheme [35] proposed for IoT enables devices, but the scheme suffers from insider attacks and cannot provide anonymity. Furthermore, the scheme [36] is vulnerable to impersonation and password guessing attacks. An ECC-based authentication protocol was proposed in [37]. However, the scheme cannot resist impersonation and offline password guessing attacks. In contrast, the scheme [38] suffers from offline password guessing attacks and cannot provide anonymity. Furthermore, an ECC-based three-factor authentication for a multi-server environment is proposed by [31] and cannot resist impersonation attacks and is unable to provide perfect forward secrecy. Finally, authentication schemes [39–41] are proposed for VANETs. However, these schemes have security vulnerabilities. For example, the scheme [39] is vulnerable to replay attacks, while the schemes [40, 41] have traceability issues. Finally, the author [42] proposed an anonymous authentication scheme for mobile devices in a public cloud server. The scheme [42] achieved all the security vulnerabilities of the scheme [43], and the communication and computation costs are also less. In the end, we identify some flaws in the scheme [2], and these flaws are discussed in detail under:(i)
Anonymity and untraceability: In the protocol [2], the server identity is transmitted openly over an insecure network. Therefore, the A can easily intercept messages transmitted among users, the registration center, and the server. Thus, the proposed protocol cannot fulfil the property of anonymity and untraceability.(ii)
Man in the Middle Attack: As we know that the protocol did not provide anonymity and untraceability. Therefore, theA can pretend to be a fake server and start communicating with peers. Thus, the A easily launches a man in a middle attack.(iii)
Secret Key disclosure Attack: The server’s identity is known toA. Therefore, the A can easily impersonate the server and fool the registration server. Once the A can impersonate the server, it easily gets the registration server secret key. Therefore, the scheme is vulnerable to secret key disclosure attacks.(iv)
Server Impersonation Attack: As we know, theA can easily obtain the server’s identity, which is transmitted openly on an insecure channel. Therefore, the A can easily impersonate the server.


## 3. Proposed Protocol

Our proposed scheme is based on a symmetric key authentication protocol for IoT devices in public cloud environments. Our protocol is described under:


### 3.1. Deployment Phase

The registration server generates secret key SKps and sends them to the public cloud server (PS). The public cloud server stores the SKps. Furthermore, the registration server assigns unique identities to IoT-enabled devices. IDi = {1, 2, 3, 4, …, n}. The registration server generates a secret key for IoT devices SKi and stores it in each IoT device. Table 1 shows the notations and their descriptions of our proposed scheme.Table 1
Notations and description.
NotationsDescriptionIDuUser identityIDpsPublic cloud server identityPSPublic cloud serverMSKupsMaster shared key b/w user and PSSKpsSecret key of public cloud serverSKuSecret key of user||,h(.)Concatenation, hash functionGen()GenerateIDiIoT device identityRSRegistration server∮∯Fuzzy extractorMSKipsMaster shared key b/w IoT and PSSKiThe secret key to IoT deviceSKSession key⊕, AXOR operator, adversaryRep()Reproduce


### 3.2. User Registration Phase

The user generates a random numberru and selects identity and password IDu, PWu. The user calculates Gen (BIO) = (∮∯. The user further computes PIDu = h(IDu||∯, Pu = h (PWu|| ∯. The user sends (PIDu, Pu, ru) toward the registration server. The registration server calculates MSKups = h(PIDu||SKps||ru), and U1 = h(ru||Pu) ⊕ MSKups. The registration server sends MSKups to the public cloud server while sending U1 to the user. The PS computes: Nu = h(IDps||SKps) ⊕ MSKUPS and X = h(IDu||ru||MSKups). The cloud server store (X, Nu) and send X to a user. After receiving (U1, X), the user further calculates M = h(IDu||PWu||∯, U2 = EMSKups(U1), U3 = h(PIDu||Pu) ⊕ ru, U4 = h(PIDu||Pu||ru). The user store (U2, U3, U4, X).


### 3.3. IoT Device Registration Phase

The IoT device select random numberri and calculate PIDi = h(IDi||ri) and send (PIDi, ri) towards registration server. After receiving the credentials from IoT device, the registration server further calculates MSKips = h(PIDi||SKps||ri). The registration server sends (PIDi, ri) to a public cloud server. The public cloud server is stored (PIDi, ri). The registration server sends MSKips to the IoT device. The IoT device calculate D1 = h(IDi||SKi) ⊕ ri, D2 = MSKips ⊕ h(SKi||ri). The IoT device stores D1 and D2.


### 3.4. Login and Authentication Phase

This phase of the protocol is shown in Table 2 and completed in the following steps:(i)
The user enters identity and password IDu, PWu and computes ∯ = rep (BIO, ∮​), PIDu = h(IDu||∯Pu = h(PWu||∯, M = h(IDu||PWu||∮), U1 = DM(U2), ru = U3 ⊕ h(PIDu||Pu), MSKups = U1 ⊕ h(ru||Pu) and check U4? = h(PIDu||Pu||ru). The user selects Select TLA1 and r2 and further calculate S1 = (IDi||r2) ⊕ MSKups ⊕ TLA1, S2 = PIDu ⊕ h(MSKups||r2||TLA1), S3 = h(PIDU||MSKups||r2||TLA1) and forward Message1{S1, S2, S3, X, TLA1} towards PS.(ii)
The public cloud server check CheckTLA1-T ≤ΔT, MSKups = h(IDps||SKps) ⊕ Nu, (IDi||r2) = S1 ⊕ MSKups  ⊕ TLA1, PIDu = S2 ⊕ h(MSKups||r2||TLA1), S3? = h(PIDu||MSKups||r2||TLA1). The public cloud server selects timestamp TLA2, and random number r3. The PS further calculates MSKips = h(IDi||SKps), S4 =  (PIDu||IDps||r2||r3) ⊕ h(IDi||MSKips||TLA2), S5 =  h(PIDu||IDps||MSKips||r2||r3||TLA2) and send Message2{S4, S5, TLA2} towards IoT device through open network channel.(iii)
The IoT device CheckTLA2-T ≤ΔT and further calculate ri = D1 ⊕ h(IDi||SKi), MSKips = D2 ⊕ h(SKi||ri), (PIDu||IDps||r2||r3) = S4 ⊕ h(IDi||MSKips||TLA2), and verify S5? = h (PIDu||IDps||MSKips||r2||r3||TLA2). The IoT selects timestamp TLA3 and random number r4. Now, the IoT device further calculates, S6 = h(MSKips||PIDi||IDps||TLA3) ⊕ r4,SK = h(r2||r3||r4||PIDu||IDps||IDi), S7 = h(IDi||r4||MSKips||SK||TLA3). The IoT device sends back Message3{S6, S7, TLA3} towards PS.(iv)
The PS first checkTLA3-T ≤ΔT and computes r4 = S6 ⊕ h(MSKips||PIDi||IDps||TLA3), SK = h(r2||r3||r4||PIDu||IDps||IDi), and verify S7? = h(IDi||r4||MSKips||SK||TLA3). Now, the PS select timestamp TLA4 and further calculate S8 = (IDps||r3||r4) ⊕ h(PIDu||MSKups||r2||TLA4), S9 = h(PIDu||IDps||r2||r3||SK||TLA4), Xnew = h(IDu||r3||MSKups) and send Message4 = {S8, S9, TLA4} back to user.(v)
The User verify timestampTLA4-T ≤ΔT and computes (IDps||r3||r4) = S8 ⊕ h (PIDu||MSKups||r2||TLA4), SK = h(r2||r3||r4||PIDu||IDps||IDi), and verify S9 ? = h(PIDu||IDps||r2||r3||SK||TLA4). The user update X = h(IDu||r3||MSKups).Table 2
Login and authentication phase.
UserPublic cloud server (PS)IOT deviceIDu, PWuComputes:∯ = rep(BIO, ∮​)PIDu = h(IDu||∯Pu = h(PWu||∯M = h(IDu||PWu||∯U1 = DM(U2)ru = U3 ⊕ h(PIDu||Pu)MSKups = U1 ⊕ h(ru||Pu)U4? = h(PIDu||Pu||ru)SelectTLA1 and r2S1 = (IDu||r2) ⊕ MSKups ⊕ TLA1S2 = PIDu ⊕ h(MSKups||r2||TLA1)S3 = h(PIDU||MSKups||r2||TLA1)Message1S1,S2,S3,TLA1⟶CheckTLA1-T ≤ΔTMSKups = h(IDps||SKps) ⊕ Nu(IDi||r2) = S1 ⊕ MSKups ⊕ TLA1PIDu = S2 ⊕ h(MSKups||r2||TLA1)S3? = h(PIDu||MSKups||r2||TLA1)SelectTLA2, r3MSKips = h(IDi||SKps)S4 = (PIDu||IDps||r2||r3) ⊕ h(IDi||MSKips||TLA2)S5 = h(PIDu||IDps||MSKips||r2||r3||TLA2)Message2S4,S5,TLA2⟶CheckTLA2-T ≤Δ Tri = D1 ⊕ h(IDi||SKi)MSKips = D2 ⊕ h(SKi||ri)(PIDu||IDps||r2||r3) = S4 ⊕ h(IDi||MSKips||TLA2)S5? = h(PIDu||IDps||MSKips||r2||r3||TLA2)SelectTLA3 and r4S6 = h(MSKips||PIDi||IDps||TLA3) ⊕ r4SK = h(r2||r3||r4||PIDu||IDps||IDi)S7 = h(IDi||r4||MSKips||SK||TLA3)Message3{S6, S7, TLA3} Message3S6,S7,TLA3⟵CheckTLA3-T ≤Δ Tr4 = S6 ⊕ h(MSKips||PIDi||IDps||TLA3)SK = h(r2||r3||r4||PIDu||IDps||IDi)S7? = h(IDi||r4||MSKips||SK||TLA3)SelectTLA4S8= (IDps||r3||r4) ⊕ h(PIDu||MSKups||r2||TLA4)S9 = h(PIDu||IDps||r2||r3||SK||TLA4)Xnew = h(IDu||r3||MSKups)Message4S8,S9,TLA4⟵CheckTLA4-T ≤Δ T(IDps||r3||r4) = S8 ⊕ h(PIDu||MSKups||r2||TLA4)SK = h(r2||r3||r4||PIDu||IDps||IDi)S9? = h(PIDu||IDps||r2||r3||SK||TLA4)X = h(IDu||r3||MSKups)


### 3.5. Biometric and Password Change Phase

(i)
Enter identity IDu, and old password PWuP, and imprints old biometric BIOP.(ii)
Computes∯∗ = rep (BIOP, ∮​∗), PIDu∗ = h(IDu|| ∯∗), Pu∗ = h(PWuP||∯∗), MSKups∗ = h(PIDu∗||SKps||ru), U1∗ = DMSKups∗(U2), U3∗ = h(PIDu∗||Pu∗) ⊕ ru, and U4∗ = h(PIDu∗||Pu∗||ru) and check U4∗? = U4. If true, then allowed to input new password and imprint new BIO otherwise, terminate the connection.(iii)
The User inputs a new password PWUN and imprints a new biometric BION.(iv)
Computes∯N = rep (BION, ∮​N),, PIDuN = h(IDu||∯N), PuN = h(PWuN||∯N), MSKupsN = h(PIDuN||SKps||ru), U2N = EMSKupsN(U1), U3N = h(PIDuN||PuN) ⊕ ru, and U4N = h(PIDuN||PuN||ru) and update (U2N, U3N, U4N).


## 3.1. Deployment Phase

The registration server generates secret key SKps and sends them to the public cloud server (PS). The public cloud server stores the SKps. Furthermore, the registration server assigns unique identities to IoT-enabled devices. IDi = {1, 2, 3, 4, …, n}. The registration server generates a secret key for IoT devices SKi and stores it in each IoT device. Table 1 shows the notations and their descriptions of our proposed scheme.Table 1
Notations and description.
NotationsDescriptionIDuUser identityIDpsPublic cloud server identityPSPublic cloud serverMSKupsMaster shared key b/w user and PSSKpsSecret key of public cloud serverSKuSecret key of user||,h(.)Concatenation, hash functionGen()GenerateIDiIoT device identityRSRegistration server∮∯Fuzzy extractorMSKipsMaster shared key b/w IoT and PSSKiThe secret key to IoT deviceSKSession key⊕, AXOR operator, adversaryRep()Reproduce


## 3.2. User Registration Phase

The user generates a random numberru and selects identity and password IDu, PWu. The user calculates Gen (BIO) = (∮∯. The user further computes PIDu = h(IDu||∯, Pu = h (PWu|| ∯. The user sends (PIDu, Pu, ru) toward the registration server. The registration server calculates MSKups = h(PIDu||SKps||ru), and U1 = h(ru||Pu) ⊕ MSKups. The registration server sends MSKups to the public cloud server while sending U1 to the user. The PS computes: Nu = h(IDps||SKps) ⊕ MSKUPS and X = h(IDu||ru||MSKups). The cloud server store (X, Nu) and send X to a user. After receiving (U1, X), the user further calculates M = h(IDu||PWu||∯, U2 = EMSKups(U1), U3 = h(PIDu||Pu) ⊕ ru, U4 = h(PIDu||Pu||ru). The user store (U2, U3, U4, X).


## 3.3. IoT Device Registration Phase

The IoT device select random numberri and calculate PIDi = h(IDi||ri) and send (PIDi, ri) towards registration server. After receiving the credentials from IoT device, the registration server further calculates MSKips = h(PIDi||SKps||ri). The registration server sends (PIDi, ri) to a public cloud server. The public cloud server is stored (PIDi, ri). The registration server sends MSKips to the IoT device. The IoT device calculate D1 = h(IDi||SKi) ⊕ ri, D2 = MSKips ⊕ h(SKi||ri). The IoT device stores D1 and D2.


## 3.4. Login and Authentication Phase

This phase of the protocol is shown in Table 2 and completed in the following steps:(i)
The user enters identity and password IDu, PWu and computes ∯ = rep (BIO, ∮​), PIDu = h(IDu||∯Pu = h(PWu||∯, M = h(IDu||PWu||∮), U1 = DM(U2), ru = U3 ⊕ h(PIDu||Pu), MSKups = U1 ⊕ h(ru||Pu) and check U4? = h(PIDu||Pu||ru). The user selects Select TLA1 and r2 and further calculate S1 = (IDi||r2) ⊕ MSKups ⊕ TLA1, S2 = PIDu ⊕ h(MSKups||r2||TLA1), S3 = h(PIDU||MSKups||r2||TLA1) and forward Message1{S1, S2, S3, X, TLA1} towards PS.(ii)
The public cloud server check CheckTLA1-T ≤ΔT, MSKups = h(IDps||SKps) ⊕ Nu, (IDi||r2) = S1 ⊕ MSKups  ⊕ TLA1, PIDu = S2 ⊕ h(MSKups||r2||TLA1), S3? = h(PIDu||MSKups||r2||TLA1). The public cloud server selects timestamp TLA2, and random number r3. The PS further calculates MSKips = h(IDi||SKps), S4 =  (PIDu||IDps||r2||r3) ⊕ h(IDi||MSKips||TLA2), S5 =  h(PIDu||IDps||MSKips||r2||r3||TLA2) and send Message2{S4, S5, TLA2} towards IoT device through open network channel.(iii)
The IoT device CheckTLA2-T ≤ΔT and further calculate ri = D1 ⊕ h(IDi||SKi), MSKips = D2 ⊕ h(SKi||ri), (PIDu||IDps||r2||r3) = S4 ⊕ h(IDi||MSKips||TLA2), and verify S5? = h (PIDu||IDps||MSKips||r2||r3||TLA2). The IoT selects timestamp TLA3 and random number r4. Now, the IoT device further calculates, S6 = h(MSKips||PIDi||IDps||TLA3) ⊕ r4,SK = h(r2||r3||r4||PIDu||IDps||IDi), S7 = h(IDi||r4||MSKips||SK||TLA3). The IoT device sends back Message3{S6, S7, TLA3} towards PS.(iv)
The PS first checkTLA3-T ≤ΔT and computes r4 = S6 ⊕ h(MSKips||PIDi||IDps||TLA3), SK = h(r2||r3||r4||PIDu||IDps||IDi), and verify S7? = h(IDi||r4||MSKips||SK||TLA3). Now, the PS select timestamp TLA4 and further calculate S8 = (IDps||r3||r4) ⊕ h(PIDu||MSKups||r2||TLA4), S9 = h(PIDu||IDps||r2||r3||SK||TLA4), Xnew = h(IDu||r3||MSKups) and send Message4 = {S8, S9, TLA4} back to user.(v)
The User verify timestampTLA4-T ≤ΔT and computes (IDps||r3||r4) = S8 ⊕ h (PIDu||MSKups||r2||TLA4), SK = h(r2||r3||r4||PIDu||IDps||IDi), and verify S9 ? = h(PIDu||IDps||r2||r3||SK||TLA4). The user update X = h(IDu||r3||MSKups).Table 2
Login and authentication phase.
UserPublic cloud server (PS)IOT deviceIDu, PWuComputes:∯ = rep(BIO, ∮​)PIDu = h(IDu||∯Pu = h(PWu||∯M = h(IDu||PWu||∯U1 = DM(U2)ru = U3 ⊕ h(PIDu||Pu)MSKups = U1 ⊕ h(ru||Pu)U4? = h(PIDu||Pu||ru)SelectTLA1 and r2S1 = (IDu||r2) ⊕ MSKups ⊕ TLA1S2 = PIDu ⊕ h(MSKups||r2||TLA1)S3 = h(PIDU||MSKups||r2||TLA1)Message1S1,S2,S3,TLA1⟶CheckTLA1-T ≤ΔTMSKups = h(IDps||SKps) ⊕ Nu(IDi||r2) = S1 ⊕ MSKups ⊕ TLA1PIDu = S2 ⊕ h(MSKups||r2||TLA1)S3? = h(PIDu||MSKups||r2||TLA1)SelectTLA2, r3MSKips = h(IDi||SKps)S4 = (PIDu||IDps||r2||r3) ⊕ h(IDi||MSKips||TLA2)S5 = h(PIDu||IDps||MSKips||r2||r3||TLA2)Message2S4,S5,TLA2⟶CheckTLA2-T ≤Δ Tri = D1 ⊕ h(IDi||SKi)MSKips = D2 ⊕ h(SKi||ri)(PIDu||IDps||r2||r3) = S4 ⊕ h(IDi||MSKips||TLA2)S5? = h(PIDu||IDps||MSKips||r2||r3||TLA2)SelectTLA3 and r4S6 = h(MSKips||PIDi||IDps||TLA3) ⊕ r4SK = h(r2||r3||r4||PIDu||IDps||IDi)S7 = h(IDi||r4||MSKips||SK||TLA3)Message3{S6, S7, TLA3} Message3S6,S7,TLA3⟵CheckTLA3-T ≤Δ Tr4 = S6 ⊕ h(MSKips||PIDi||IDps||TLA3)SK = h(r2||r3||r4||PIDu||IDps||IDi)S7? = h(IDi||r4||MSKips||SK||TLA3)SelectTLA4S8= (IDps||r3||r4) ⊕ h(PIDu||MSKups||r2||TLA4)S9 = h(PIDu||IDps||r2||r3||SK||TLA4)Xnew = h(IDu||r3||MSKups)Message4S8,S9,TLA4⟵CheckTLA4-T ≤Δ T(IDps||r3||r4) = S8 ⊕ h(PIDu||MSKups||r2||TLA4)SK = h(r2||r3||r4||PIDu||IDps||IDi)S9? = h(PIDu||IDps||r2||r3||SK||TLA4)X = h(IDu||r3||MSKups)


## 3.5. Biometric and Password Change Phase

(i)
Enter identity IDu, and old password PWuP, and imprints old biometric BIOP.(ii)
Computes∯∗ = rep (BIOP, ∮​∗), PIDu∗ = h(IDu|| ∯∗), Pu∗ = h(PWuP||∯∗), MSKups∗ = h(PIDu∗||SKps||ru), U1∗ = DMSKups∗(U2), U3∗ = h(PIDu∗||Pu∗) ⊕ ru, and U4∗ = h(PIDu∗||Pu∗||ru) and check U4∗? = U4. If true, then allowed to input new password and imprint new BIO otherwise, terminate the connection.(iii)
The User inputs a new password PWUN and imprints a new biometric BION.(iv)
Computes∯N = rep (BION, ∮​N),, PIDuN = h(IDu||∯N), PuN = h(PWuN||∯N), MSKupsN = h(PIDuN||SKps||ru), U2N = EMSKupsN(U1), U3N = h(PIDuN||PuN) ⊕ ru, and U4N = h(PIDuN||PuN||ru) and update (U2N, U3N, U4N).


## 4. Formal Security Analysis

In the section of our research article, we will investigate, analyze, discuss, and explain our proposed scheme against all potential attacks using ProVerif, the ROR model, and informal security discussions.


### 4.1. ProVerif Code

ProVerif is a simulation toolkit that is used to simulate cryptographic algorithms. ProVerif checks the key secrecy, reachability, and confidentiality [44]. Figure 2 shows our proposed scheme simulation code result, and according to the ProVerif simulation result, our proposed scheme is secure.Figure 2
ProVerif simulation result.


### 4.2. ROR Model

In this section, we evaluate our proposed schemeSK by using the ROR model [45]. Three participants are involved in our scheme such as user PuT1, public cloud server PpsT2, and IoT-enabled device PiT3. We demonstrate each query used in ROR model such as Execute, CorruptSC, Reveal, Send, and Test.Theorem 1.
The AdvA has the advantage of violating SK of our scheme, the inequality ADVA≤qh2/HASH+2C.qs/2lf. qs denoted the hash queries, and C, l, and f are Zipf values [46].Proof.
Four Games in a sequenceGameg: {g = 0, 1, 2, 3} are played by A. The AdvA has the probability of winning all the Games. These Games are discussed below:
Gameg0: In this Gameg0, the A executes a real attack and tries to guess a bit in order to win the Gameg0.(1)ADVA=2.ADVA,Gameg0−1.
Gameg1: The A trying to eavesdrop attack on a proposed scheme where all messages transmitted are intercepted by using Execute. The A perform Test and Reveal to check that the message has SK or random numbers. The A need secret values such as SKu, SKps, SKi, PIDu, PIDi, and random numbers to construct SK = h(r2||r3||r4||PIDu||IDps||IDi). Therefore, based on this, we obtained(2)ADVA,Gameg1=ADVA,Gameg0.
Gameg2: In this game, Gameg2, the A trying actively/passively attack our scheme. The A using the Send query and Hash query. The A intercepted all exchanged messages such as Message1{S1, S2, S3, TLA1}, Message2{S4, S5, TLA2}, Message3{S6, S7, TLA3}, and Message4 = {S8, S9, TLA4}. Furthermore, these messages are protected using secret keys, random numbers, and hashing h(.). Therefore, we obtain(3)ADVA,Gameg2−ADVA,Gameg1≤C.qsendqs2lf.
Gameg3: The A trying to get {U2, U2, U3} from IoT device memory using CorruptSC through power analysis attack. The A trying to get password PWu using offline password guessing attack. However, in our scheme, the A cannot get a password using Send query. Therefore, we get(4)ADVA,Gameg2−ADVA,Gameg1≤qh2HASH.
After playingGameg0, Gameg1, Gameg2, and Gameg3. The A tries to guess the bit to win the game using the Test query. Hence, we get(5)ADVA,Gameg3=12.
By applying (1), (2) and (5), we obtained(6)12ADVA=ADVA,Gameg0−12=ADVA,Gameg1−12=ADVA,Gameg2−12=ADVA,Gameg1−ADVA,Gameg3.
Now by using (4), (5), and (6), we get(7)12ADVA=ADVA,Gameg1−ADVA,Gameg3≤ADVA,Gameg1−ADVA,Gameg2+ADVA,Gameg2−ADVA,Gameg3≤qh2HASH+C.qsend2qs2lf.
Equation (7) is multiplied by 2 on both sides, and we get(8)ADVA≤qh2HASH+2C.qsend2,qs2lf.
Hence, the theorem is proved.


### 4.3. Shared Session Key Correctness

In this section, we will prove that the shared session key for communicating participants is the same. During in login and authentication phase the shared session key is calculated by IoT device isSK = h(r2||r3||r4||PIDu||IDps||IDi) and the receiver end the user calculated the shared session key SK = h(r2||r3||r4||PIDu||IDps||IDi). In the initiator IoT device received S4 = (PIDu||IDps||r2||r3) ⊕ h(IDi||MSKips||TLA2) and S5 = h(PIDu||IDps||MSKips||r2||r3||TLA2). It successfully computed (PIDu||IDps||r2||r3) = S4 ⊕ h (IDi||MSKips||TLA2) and verify S5 = h(PIDu||IDps||MSKips||r2||r3||TLA2). Furthermore, the IoT device computed S6 = h(MSKips||PIDi||IDps||TLA3) ⊕ r4 and S7 = h(IDi||r4||MSKips||SK||TLA3) and forward it to the public cloud server. Similarly, likewise IoT device, the public cloud server successfully generated r4 = S6 ⊕ h(MSKips||PIDi||IDps||TLA3) and verify S7 = h(IDi||r4||MSKips||SK||TLA3) and further calculated S8 = (IDps||r3||r4) ⊕ h(PIDu||MSKups||r2||TLA4) and S9 = h(PIDu||IDps||r2||r3||SK||TLA4). The public cloud server forward S8 and S9. The user successfully computes (IDps||r3||r4) = S8 ⊕ h(PIDu||MSKups||r2||TLA4) and verify S9. Therefore, the communicating participants successfully get the required credentials to construct the shared session key.


## 4.1. ProVerif Code

ProVerif is a simulation toolkit that is used to simulate cryptographic algorithms. ProVerif checks the key secrecy, reachability, and confidentiality [44]. Figure 2 shows our proposed scheme simulation code result, and according to the ProVerif simulation result, our proposed scheme is secure.Figure 2
ProVerif simulation result.


## 4.2. ROR Model

In this section, we evaluate our proposed schemeSK by using the ROR model [45]. Three participants are involved in our scheme such as user PuT1, public cloud server PpsT2, and IoT-enabled device PiT3. We demonstrate each query used in ROR model such as Execute, CorruptSC, Reveal, Send, and Test.Theorem 1.
The AdvA has the advantage of violating SK of our scheme, the inequality ADVA≤qh2/HASH+2C.qs/2lf. qs denoted the hash queries, and C, l, and f are Zipf values [46].Proof.
Four Games in a sequenceGameg: {g = 0, 1, 2, 3} are played by A. The AdvA has the probability of winning all the Games. These Games are discussed below:
Gameg0: In this Gameg0, the A executes a real attack and tries to guess a bit in order to win the Gameg0.(1)ADVA=2.ADVA,Gameg0−1.
Gameg1: The A trying to eavesdrop attack on a proposed scheme where all messages transmitted are intercepted by using Execute. The A perform Test and Reveal to check that the message has SK or random numbers. The A need secret values such as SKu, SKps, SKi, PIDu, PIDi, and random numbers to construct SK = h(r2||r3||r4||PIDu||IDps||IDi). Therefore, based on this, we obtained(2)ADVA,Gameg1=ADVA,Gameg0.
Gameg2: In this game, Gameg2, the A trying actively/passively attack our scheme. The A using the Send query and Hash query. The A intercepted all exchanged messages such as Message1{S1, S2, S3, TLA1}, Message2{S4, S5, TLA2}, Message3{S6, S7, TLA3}, and Message4 = {S8, S9, TLA4}. Furthermore, these messages are protected using secret keys, random numbers, and hashing h(.). Therefore, we obtain(3)ADVA,Gameg2−ADVA,Gameg1≤C.qsendqs2lf.
Gameg3: The A trying to get {U2, U2, U3} from IoT device memory using CorruptSC through power analysis attack. The A trying to get password PWu using offline password guessing attack. However, in our scheme, the A cannot get a password using Send query. Therefore, we get(4)ADVA,Gameg2−ADVA,Gameg1≤qh2HASH.
After playingGameg0, Gameg1, Gameg2, and Gameg3. The A tries to guess the bit to win the game using the Test query. Hence, we get(5)ADVA,Gameg3=12.
By applying (1), (2) and (5), we obtained(6)12ADVA=ADVA,Gameg0−12=ADVA,Gameg1−12=ADVA,Gameg2−12=ADVA,Gameg1−ADVA,Gameg3.
Now by using (4), (5), and (6), we get(7)12ADVA=ADVA,Gameg1−ADVA,Gameg3≤ADVA,Gameg1−ADVA,Gameg2+ADVA,Gameg2−ADVA,Gameg3≤qh2HASH+C.qsend2qs2lf.
Equation (7) is multiplied by 2 on both sides, and we get(8)ADVA≤qh2HASH+2C.qsend2,qs2lf.
Hence, the theorem is proved.


## 4.3. Shared Session Key Correctness

In this section, we will prove that the shared session key for communicating participants is the same. During in login and authentication phase the shared session key is calculated by IoT device isSK = h(r2||r3||r4||PIDu||IDps||IDi) and the receiver end the user calculated the shared session key SK = h(r2||r3||r4||PIDu||IDps||IDi). In the initiator IoT device received S4 = (PIDu||IDps||r2||r3) ⊕ h(IDi||MSKips||TLA2) and S5 = h(PIDu||IDps||MSKips||r2||r3||TLA2). It successfully computed (PIDu||IDps||r2||r3) = S4 ⊕ h (IDi||MSKips||TLA2) and verify S5 = h(PIDu||IDps||MSKips||r2||r3||TLA2). Furthermore, the IoT device computed S6 = h(MSKips||PIDi||IDps||TLA3) ⊕ r4 and S7 = h(IDi||r4||MSKips||SK||TLA3) and forward it to the public cloud server. Similarly, likewise IoT device, the public cloud server successfully generated r4 = S6 ⊕ h(MSKips||PIDi||IDps||TLA3) and verify S7 = h(IDi||r4||MSKips||SK||TLA3) and further calculated S8 = (IDps||r3||r4) ⊕ h(PIDu||MSKups||r2||TLA4) and S9 = h(PIDu||IDps||r2||r3||SK||TLA4). The public cloud server forward S8 and S9. The user successfully computes (IDps||r3||r4) = S8 ⊕ h(PIDu||MSKups||r2||TLA4) and verify S9. Therefore, the communicating participants successfully get the required credentials to construct the shared session key.


## 5. Informal Security Analysis

Informal security discussion and explanation of our proposed architecture are under:(1)
Impersonation Attack: TheA trying to impersonate user, public cloud server, and IoT device. It will need to calculate the authentication request messages such as message1 and message4. However, it is challenging for A to generate secret key SKps, random numbers, and PIDu. Therefore, our proposed scheme resists impersonation attacks because the A is unable to compute the values mentioned above.(2)
IoT Device Capture Attack: Let us suppose the IoT device is physically captured byA and A trying to extract secret values such as {D1, D2}. However, the A cannot compute MSKips without knowing the secret key of public cloud SKps, random number r1, and pseudo-identity PIDi. Therefore, the proposed scheme resists IoT device capture attacks.(3)
Man-in-the-Middle Attack: Suppose theA eavesdrop on all transmitted messages among IoT devices, users, and public cloud servers, then it is possible to launch a MITM attack. However, the A cannot construct the transmitted messages because these messages are protected with secret keys {SKi, SKu, SKps}, identities {IDi, IDu, IDps}, and random numbers {r1, r2, r3, r4}. Thus, our proposed scheme is secure against MITM attacks.(4)
Session Key Disclosure Attack: Let suppose theA obtain {U2, U3, U4} that are stored on the user side. However, the A should get the random numbers {r1, r2, r3, r4} to construct session key Sk. Moreover, the A also needs to know the pseudo-identity of user PIDu, cloud server identity IDps, and IoT identity IDi. Hence, our scheme resists session key disclosure attacks.(5)
Offline Password Guessing Attack: Suppose theA access to {U2, U3, U4} is stored on the user side. These values are constructed in a way that the A cannot get a password from it, such as U2 = EMK(U1), U3 = h(PIDu||Pu) ⊕ ru, and U4 = h(PIDu||Pu||ru). The A needs random number r1 and ⊕ to construct those values. Therefore, our scheme is secure against offline password guessing attacks.(6)
Anonymity and untraceability: Suppose theA access to all transmitted messages during the login and authentication phase. However, the A cannot get the identities {IDu, IDps, IDi}, pseudo identities {PIDi, PIDu} without knowing the secret keys. Furthermore, the random numbers and timestamps are different in each session. Therefore, the A cannot trace any peers. Hence, the proposed scheme provides anonymity and untraceability.(7)
Mutual Authentication: In our proposed architecture, all parties mutual authenticate each other; after receiving, Message1{S1, S2, S3, TLA1} from a user, the public cloud server authenticates the user using S3? = h(PIDi||MSKups||r2||TLA1) while the IoT device authenticate PS using S5? = h(PIDu||IDps||MSKips||r2||r3||TLA2). Furthermore, the PS authenticate IoT devices using S7? = h(IDi||r4||MSKips||Sk||TLA3) and the user authenticate PS using S9? = h(PIDu||IDps||r2||r3||SK||TLA4). Hence, our proposed architecture provides mutual authentication.(8)
Replay Attack: If theA intercept previous session transmitted messages such as Message1{S1, S2, S3, TLA1}, Message2{S4, S5, TLA2}, Message3{S6, S7, TLA3}, and Message4 = {S8, S9, TLA4}. After the interception, the A trying to resend those messages again, then our proposed scheme checks the validation of timestamps. Furthermore, all transmitted messages are protected using secret keys and random numbers. Hence, our scheme is resilient to replay attacks.(9)
Perfect Forward Secrecy: In our proposed scheme, theA cannot construct the session key if it is compromised previous session key SK. Because the A will need MSKups, ri, PIDi, PIDu, and MSKips to construct the session key. Therefore, the proposed scheme provides perfect forward secrecy.


## 6. Performance Analysis

We evaluate the proposed scenario regarding security features, communication, and computation costs. We consider the existing protocols and compare them with our scheme. Our scheme provides foolproof security and lower computation and communication costs.


### 6.1. Security Features

This section evaluates our proposed scheme in terms of security features. We compared our proposed protocol with other recent related existing schemes. Table3 compares our scheme with the existing schemes and shows that our scheme performs better than other schemes in terms of security features.Table 3
Security features.
Features↓⟶Schemes[2][47][48][49][50][51][52][53][54][35][55]OurImpersonation attack∞∝✓✓✓✓✓✓✓✓✓✓Offline password guessing attack✓✓✓✓✓✓✓✓✓✓-✓Man-in-the-middle attack∞∞✓✓✓✓✓✓✓✓-✓Session key disclosure attack∞∞✓✓✓✓✓✓✓✓✓✓Anonymity and untraceability∞∞✓✓✓✓✓✓✓∝✓✓Mutual authentication✓✓✓✓✓✓✓✓✓✓✓✓Replay attack✓✓✓✓✓✓✓✓✓-✓Perfect forward secrecy✓✓✓✓✓✓✓✓✓✓✓Stolen device attack—————∝∝∝———✓✓: secure,∞: insecure, —: not considered.


### 6.2. Communication Cost

We calculate our proposed scheme communication cost in this section. We choose SH-1, where identities are equal to 160 bits, random numbers are 160, and timestamp 32 bits. For encryption and decryption, we select AES-128, which takes 128 bits as an input and output. The hash function is 160 bits. Our scheme authentication is completed in four rounds. The message transmitted from the user to the public cloud server is message1 = {512}. From public cloud server to IoT device message2 = {352} while from IoT device to public cloud server is message3 = {352} and from public cloud server to user is message4 = {352}. The total communication cost is 1568 bits, as shown in Figure 3.Figure 3
Communication cost.


### 6.3. Computation Cost

We compute the computation cost of our proposed scheme in this section. We adopted the work done by [54]. Tm represents multiplication time, Th is a one-way hash function, and TE and TD are encryption and decryption. The operation execution time in ms is mentioned in Table 4. Furthermore, our scheme computation cost equals = 0.266 ms, as shown in Figure 4.Table 4
Operation and execution time.
OperationExecution time in msTh0.00097TA0.0028TE0.109TD0.0036TM0.0035Figure 4
Computation cost.


## 6.1. Security Features

This section evaluates our proposed scheme in terms of security features. We compared our proposed protocol with other recent related existing schemes. Table3 compares our scheme with the existing schemes and shows that our scheme performs better than other schemes in terms of security features.Table 3
Security features.
Features↓⟶Schemes[2][47][48][49][50][51][52][53][54][35][55]OurImpersonation attack∞∝✓✓✓✓✓✓✓✓✓✓Offline password guessing attack✓✓✓✓✓✓✓✓✓✓-✓Man-in-the-middle attack∞∞✓✓✓✓✓✓✓✓-✓Session key disclosure attack∞∞✓✓✓✓✓✓✓✓✓✓Anonymity and untraceability∞∞✓✓✓✓✓✓✓∝✓✓Mutual authentication✓✓✓✓✓✓✓✓✓✓✓✓Replay attack✓✓✓✓✓✓✓✓✓-✓Perfect forward secrecy✓✓✓✓✓✓✓✓✓✓✓Stolen device attack—————∝∝∝———✓✓: secure,∞: insecure, —: not considered.


## 6.2. Communication Cost

We calculate our proposed scheme communication cost in this section. We choose SH-1, where identities are equal to 160 bits, random numbers are 160, and timestamp 32 bits. For encryption and decryption, we select AES-128, which takes 128 bits as an input and output. The hash function is 160 bits. Our scheme authentication is completed in four rounds. The message transmitted from the user to the public cloud server is message1 = {512}. From public cloud server to IoT device message2 = {352} while from IoT device to public cloud server is message3 = {352} and from public cloud server to user is message4 = {352}. The total communication cost is 1568 bits, as shown in Figure 3.Figure 3
Communication cost.


## 6.3. Computation Cost

We compute the computation cost of our proposed scheme in this section. We adopted the work done by [54]. Tm represents multiplication time, Th is a one-way hash function, and TE and TD are encryption and decryption. The operation execution time in ms is mentioned in Table 4. Furthermore, our scheme computation cost equals = 0.266 ms, as shown in Figure 4.Table 4
Operation and execution time.
OperationExecution time in msTh0.00097TA0.0028TE0.109TD0.0036TM0.0035Figure 4
Computation cost.


## 7. Conclusions

As we know that the misconfiguration, unauthorized accessing of applications, and the response of cloud servers to the results generated by IoT of end-user in the cloud computing paradigm is yet to be addressed by the researchers. In this regard, we have attempted to design a security mechanism for mitigating the aforesaid issues to a maximum extent. The security analysis section of the proposed framework has been made using worldwide used techniques ROR model, ProVerif2.03, and realistic discussion. Furthermore, the performance analysis has been evaluated by considering three metrics, i.e., security features, communication, and computation costs. The comparison results show that the proposed scenario is suitable for practical implantation in the IoT using a public cloud server. In the future, we have planned to design a transitional authentication for end-users when using IoT. At the same time, its security will be conducted using AVISPA.



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*Source: 7836461-2022-11-23.xml*