Abstract
Keywords
Introduction
As an important application of Internet of Things (IoT), home-based IoT is the technology and concept of monitoring and managing household appliances through intelligent, coordinated network and technology. In general, home-based IoT is composed of numbers of heterogeneous intelligent devices, such as cameras, actuators, and smart appliances. This development leads people’s lives into a new era of science and technology. All household appliances became controllable through the Internet, so that people can enjoy the services brought about by the development of IoT, like home temperature control, energy management, telemedicine, remote devices control, and other similar services. 1 In addition, with the continuous development of consumer IoT, the number of intelligent systems will be greatly increased. As a result, individuals will increasingly rely on intelligent systems.
However, the internal network of the intelligent home area includes many differences in wireless network communication technologies. For example, Z-Wave and ZigBee 2 are the most commonly used low-power wireless communication technologies. As a multi-network convergence technology, many intelligent devices or sensors in the home area network (HAN) are always connected to the Internet using wireless communication. However, considering the insecurity of the Internet, connecting intelligent devices or sensors through the Internet will make a device vulnerable to malicious attacks. If the network of connecting intelligent devices (such as cameras and smart appliances) in HAN is inadequate, users of home-based IoT will face a more extensive security threat, including identity theft and device forgery. Because the information in home-based IoT environment is directly related to the user’s safety and vital interests, the security of information in the home-based IoT field is very demanding. However, home-based IoT products contain many security issues, so how to ensure the security of home-based IoT devices and services in the insecure environment of IoT is an urgent problem to solve. In addition, fine-grained data generated by sensor devices (SDs) and transmitted through unsafe wireless channels in HAN will raise two major security issues: (1) how to authenticate SDs in HAN in an unrecognizable situation (i.e. anonymity), and (2) how to access SDs through public networks without distinguishing home-based IoT devices.
To solve the above problems, using secure and efficient anonymous authentication, key exchange protocol is the best solution. The key point of designing anonymous authentication communication protocol for home-based IoT environment is to provide mutual authentication and key agreement for preventing illegal users from stealing information from HAN. Also, to ensure the efficiency and safety of the authentication method, the security scheme needs to satisfy the following conditions: (1) anonymity: hiding the identity of devices or sensors and activities of collecting data to prevent unauthorized tracking—even if malicious devices exist, they should not be able to reveal the identity and relationship of the devices communicating in the HAN; (2) low consumption: the processing and communicating ability of battery-powered SDs is often seriously limited by low resources—therefore, communication and computing efficiency should be considered in the scheme; and (3) security: the protocol should be able to withstand possible attacks (e.g. replay attacks, simulated attacks) for application in real home environments.
Related work
Information encryption is an important solution to security problems. The transmission process of information in an unsafe open network has always attracted the attention of researchers. Authentication and key agreement are effective solutions to this problem. It allows identity authentication among communication agents and establishes communication keys to encrypt communication information. Usually, user identity, password, and portable devices that store user information published by trusted servers are key elements for authentication. Therefore, there are many researchers focusing on designing anonymous authentication key agreement schemes for a wireless network environment with lightweight.
In 2011, Vaidya et al. 3 proposed an authentication scheme using an implicit certificate for home-based IoT area network. In their paper, the implicit certificate as a public key for each device is made by the certification authority. After running the authentication step, the scheme established a session key between two related entities where the identity of the device is transmitted as plain text. They claim that their scheme is effective, but the security analysis of the scheme does not provide detailed information. Later, Chakravorty et al. 4 proposed a framework for maintaining the security and privacy for smart homes. However, they paid attention to data security rather than device anonymity. Another data access control scheme for home-based IoT is proposed by Ryu et al. 5 Their scheme authenticated all devices which had registered to the server and provided safe access control of the data. Moreover, many traditional authentication protocols6–9 are proposed with two- or three-factor authentication. However, these authentication schemes used password and/or biological features to ensure the security of the schemes. The difference between these protocols6–9 and protocols for home-based IoT is that those authentication schemes for home-based IoT need to be automatically run by the devices in HAN.
Hoang et al. proposed an anonymous communication method based on the Onion Router (Tor) to protect intelligent appliances. 10 In their method, users use Tor to run as an anonymous browser where those surfing activities are run anonymously, but authentication is not performed. In addition, the public key encryption technology used in their scheme is too computational extensive for devices with limited resources. In the same year, Santoso et al. proposed a strong security authentication system using Elliptic Curve Cryptography (ECC). 11 Because pre-shared secret keys are utilized, their scheme did not need public key infrastructure. When the identity authentication is completed, both parties can create a shared key for the subsequent symmetric encryption. Kumar et al. 12 claimed that their session key establishment scheme for home-based IoT with authentication token was efficient and could withstand number of popular attacks such as the denial of service and eavesdropping attacks. However, the security of their scheme mainly relied on the secret keys stored by the devices, and their scheme did not consider anonymity and non-linkability.
Lu et al. 13 and Jung et al. 14 proposed anonymous authentication protocols for wireless sensor network (WSN) user, respectively. At that time, Xiong et al. found that the schemes of Lu et al. 13 and Jung et al. 14 are vulnerable to smart card loss attacks and cannot provide perfect forward security and unrealistic gateway node (GWN) search operation. 15 An improved scheme was proposed. Wang et al. 16 summarized the advantages and disadvantages of eight basic wireless sensor system architectures, attacker models, and 12 evaluation criteria for evaluating the security of wireless sensor systems. In addition, Wang et al. analyzed the authentication protocol proposed by Wu et al. 17 and Srinivas and Mukhopadhyay, 18 and found that they had the following security problems: they could not resist smart card loss attacks—user counterfeiting attacks, could not achieve user anonymity, and could not detect the wrong password in time.
Scott proposed an authenticated ID-based key exchange and remote log-in scheme with two factors. 19 In his scheme, a special pairing is used to reduce computation. Such a scheme is open to the next active insider attack. Similarly, Yu et al. 20 published a remote registration scheme for mobile networks, also with the special pairing, but in their scheme, the key agreement protocol is not considered.
Our contribution
The contributions of this article are as follows:
An anonymous authentication key agreement scheme based on pairing-based cryptography is proposed in which we guarantee the efficiency and security for home-based IoT area networks.
The security analysis of our protocol is discussed using a logic proposed by Burrows, Abadi and Needham (BAN logic). In addition, the performance analysis of the scheme is given.
Organization of the article
In this part, the organization of this article is shown as follows. The “Preliminaries” section presents the preliminaries of this article. The “Proposed key agreement protocol” section introduces the proposed anonymous authentication key agreement. Discussions are provided in the “Security and performance analysis” section. Finally, the “Conclusion” section concludes this article.
Preliminaries
Notations
The network mode for home-based IoT is shown in Figure 1. This mode includes three types of participants, that is, the home server (HS), SDs, and external user (U). The HS is rich in resources like a PC or a server station working in the HAN. The SDs are resource-constrained devices placed at home. The external users are those with mobile phones who want to access HAN from the Internet. For convenience, some notations used in this article are described in Table 1.

A network model for home-based IoT network.
Notations.
HAN: home area network.
BAN logic
BAN logic is a logic to analyze the security of authentication protocols. This logic uses the protocol’s initial assumptions and inference rules to infer other facts in order to achieve authentication goals. The basic notation for BAN logic is shown in Table 2.
The basic notation for BAN logic.
The logic rules used in this security verification are as follows.
1. Message-meaning rule
For public keys
For shared keys
For shared secrets
2. Nonce-verification rule
3. Jurisdiction rule
4. Session key rule
Bilinear maps
A type-3 pairing is a mapping
Proposed key agreement protocol
This section puts forward a new anonymous authentication key agreement scheme for home-based IoT based on pairing-based cryptography. Our scheme consists of three steps: initialization step, anonymous registration step, and anonymous authentication key agreement step. The initialization step is performed by the HS. The anonymous registration step is performed by all SDs and legal users for obtention private keys. Finally, anonymous authentication key agreement step is run for generating session key by all the participants.
Initialization setup
The HS needs to initialize some parameters for the whole system, including public parameters and secret parameters. First, the server will randomly produce a master secret
Registration
In this part, legal users and smart devices could communicate with the HS to get their private key. So, all the legal users and smart devices can store the tokens in mobiles or devices without fear of private key leakage. Generally, it is assumed that the registration can be performed through a secure channel to get the private key. But sometimes there may be no conditions to establish such a secure channel. In order to make the scheme universal, we refer to the design of registered communication scheme through public network. For a new user or device to register with the server, they must prove the ID and some temporary parameters. In return, the user or device is supplied with the private key as shown in Figures 2 and 3.

User registration algorithm.

The smart device registration algorithm.
For a mobile user:
The user picks a random number
The HS gets the The server computes the private key with a master key for the user as To ensure safe transfer of the private key to the user, the server needs to compute a session key to encrypt the private key. First, compute
Getting the cipher from the server, the user could decrypt the information and obtain the message
For a smart device:
Same as the phase of the user registration, smart device chooses a random number
The HS gets the The server computes the private key with a master key for the device as To ensure safe transfer of the private key to the device, the server needs to compute a session key to encrypt the private key. First, compute
Getting the cipher from the server, the device could decrypt the information and obtain the message
Authentication and key agreement
In this part, legal users with mobiles from the Internet can communicate with smart devices in the HAN with the help of HS. The detailed process is shown in Figure 4.
The user with smart mobile has got the private key from
The smart device wanted by the user has got the private key
The HS holds that the system secret key checks the timestamp received from the user and smart device with the following steps: After getting the message from the user, it checks the functions After getting the message from the smart device, it checks the functions
The HS holds that the system secret key checks the timestamp received from the user as
After checking the timestamp and the hash value receiving from the HS as
After checking the timestamp and the hash value receiving from the HS as
Then, the HS checks the timestamp receiving from the user and the smart device with the following steps: After getting the message from the user, it checks the functions After getting the message from the smart device, it checks the functions After checking the timestamp and the hash value receiving from the HS as
After checking the timestamp and the hash value receiving from the HS as

Anonymous authentication and key agreement.
Security and performance analysis
Security analysis
In this section, we will analyze the proposed protocol with BAN logic to prove that our protocol is secure. Through analysis, it is known that the communication between users and servers and between SDs and servers is secure in our protocol. And the communication between the user and the SD is also secure with the help of the server. At first, the messages sent over the unsecured channel in the proposed scheme are
Message 1:
Message 2:
Message 3:
Message 4:
Following security, goals must be satisfied by using BAN logic to prove that the proposed protocol is practical and valid
Goal 1:
Goal 2:
Goal 3:
Goal 4:
Goal 5:
Goal 6:
Goal 7:
Goal 8:
Goal 9:
Goal 10:
Next, some necessary assumptions about original messages are presented
A1:
A2:
A3:
A4:
A5:
A6:
A7:
A8:
A9:
A10:
A11:
A12:
A13:
A14:
A15:
A16:
A17:
A18:
A19:
Now, we are ready to prove the scheme using BAN logic as follows. From message 1, A2, and message-meaning rule, we get
P1:
P2:
From P1, P2, A3, and Nonce-verification rule, we get
P3:
P4:
As the same way, we can get
P5:
P6:
P7:
P8:
P9:
P10:
P11:
P12:
P13:
P14:
P15:
P16:
From P11, P12, A12, A13, and Jurisdiction rule, we get
P17:
P18:
From P15, P16, A14, A15, and Jurisdiction rule, we get
P19:
P20:
From P17, P18, A16, A17, and Jurisdiction rule, we get
P21:
P22:
From P19, P20, A18, A19, and Jurisdiction rule, we get
P23:
P24:
From P17, P18, P19, P20, session key rule, and freshness rule, we get
P23:
P24:
Informal security analysis
User impersonation attack
Suppose an attacker
Anonymity and untraceability
The proposed scheme supports strong user anonymity and untraceability because the mobile user and the SD send their identity encrypted with the random number for each session. Thus, the HS can only get the masked identities of the mobile users and SDs.
Key forward secrecy
The proposed scheme supports key forward secrecy. Even if an eavesdropper gets the private key of the mobile user and the SD, the eavesdropper cannot get
Strong key establishment
The mobile user and the SD establish a secure session key using authenticated Diffie–Hellman key exchange. Thus, the session key is known only to the mobile user and the SD, and equally contributed by both the mobile user and the SD.
Insider attack
In the proposed scheme, the mobile user and the SD send
Replay attack
The proposed scheme is secure against the replay attack because the mobile user, the SD, and the HS use timestamp to avoid the replay attack. If a message is replayed by the adversary, all the three entities can check the replayed message by verifying the timestamp. If the timestamp is not valid, they can discard the message.
No verifier table at HS
The HS does not maintain verifier tables for the mobile users and the SD. Therefore, the proposed scheme is free from stolen verifier attack. An adversary cannot impersonate the mobile user and the foreign server due to the absence of stolen verifier attack.
Performance analysis
The computation cost of the scheme will be discussed in detail. Before the analysis, we give some symbol definitions, as shown in Table 3. At the registration stage of our scheme, the computation of the user or SD is
The parameter definitions.
Now we will compare the performance and functionality of our scheme with other related schemes. To accurately estimate the running time, we use the MIRACL library to perform the cryptographic primitives for 1000 executions and take the arithmetic mean based on 120 MHz ARM chip. The detailed analysis results are shown in Table 4.
The performance analysis.
Conclusion
In this article, a new anonymous authentication key agreement scheme with pairing-based cryptography for home-based IoT has been proposed that ensures secure communication between SDs and users. In the HAN environment, devices collect personal and sensitive information from users and have the characteristic of having low power, low cost, and being lightweight. So, we have used a special pairing to reduce the amount of calculation. The proposed protocol masks the identity of the devices and the user. Finally, we have proved the scheme with the BAN logic. Moreover, performance analysis shows that our protocol is efficient for home-based IoT endpoints.
