A new three-factor authentication scheme overcome repeat registered attack for wireless sensor networks

. In the wireless sensor networks (WSNs), users sometimes need to access real-time information from a certain sensor node. In order to prevent unauthorized users from acquiring information from the sensor node, a lot of authentication schemes suited for the WSNs condition have been proposed. Recently, Das has proposed a secure and light-weight authentication scheme for the WSNs based on three factors, claiming that it can withstand various attacks. But after a careful analysis, there are still several security problems as follows: a) The scheme has some design flaws; b)The scheme may suffer sensor node impersonation attack; c) The scheme may suffer repeat registered attack; d) When the user access the sensor node, the scheme cannot protect the identity information of the sensor node. To solve these problems, a new scheme using the secure sketch algorithm is presented in this paper. The security of improved scheme has been analyzed by ProVerif. Thorough analysis shows that the presented scheme can provide stronger security and slight lower computation at client than Das’s protocol. What’s more, it can overcome repeat registered attack and achieve sensor node’s identity anonymity protection.


Introduction
The wireless sensor networks (WSNs) are usually deployed in harsh enviroment, such as in enemy positions or other unsafe environments. At the same time, WSNs have a lot of nature attributes, such as limited data processing ability, limited storage capacity, limited bandwidth, limited energy, and other limited factors. As the two important fields in WSNs, the sensor nodes are deployed randomly in a target field while the BS(Base Station) collects the information of all sensor nodes and manages WSNs or performs costly operation. The sensor node is insecure whereas BS is secure. Usually, If a user wants to acquire information from the sensor node without real-time requirements, he/she must communicate with the BS in order to acquire data from the sensor node. In the military or healthcare applications, the authorized user needs to access the real-time information directly from sensor nodes without the BS participation. The details are shown as figure 1. In order to ensure that unauthorized users cannot join the network or acquire any valuable information, a friendly and reliable authentication machanism becomes necessary. In 2009, Das [1] proposed a novel two-factor authentication scheme based on the smart card and the password for WSNs. This scheme has a lot of advantages, for example the base station (BS) need not to maintain a database for storing users' identities or passwords. Besides, a lot of new authentication schemes later proposed have been based on his scheme. Under some stringent assumptions just like the information stored in sensor nodes cannot be acquired or modified. Das's scheme can resist common attacks such as guessing attack, replaying attack, stealing verifier attack and so on. However, Nyang-Lee [2] pointed out Das's scheme [1] could not resist offline password guessing attack and node capture attack. In order to solve these problems, they proposed a new scheme [2] which can not only achieve secure communication between user and SN but also resist password guessing attack. Unfortunately, Nyang-Lee's scheme cannot resist denial of service (Dos). In 2010, He et al. [3] pointed out Das's scheme had both advantages such as light-weighted computation, resistance to various attacks . At the same time, the scheme has some disadvantages also which involve possible insider attack and impersonation attack. In order to exploit its strong points and avoid its weakness, He et al. [3] proposed an improved scheme. In 2011, Kumar-Lee [4] pointed out He et al.'s scheme could not achieve mutual authentication and session key establishment between the user and the sensor node. From the analysis in Kumar-Lee's scheme, we can see that He et al.'s scheme cannot achieve user anonymity. In 2012, Yoo et al. [5] proposed an efficient two-factor authentication scheme. However, this scheme could not protect user's privacy [6]. In 2013, Sun et al. [7] proposed a robust two-factor user authentication scheme. However, the analysis in [6] shows that Sun et al.'s scheme cannot achieve user privacy protection, mutual authentication and session key agreement. In 2013, Xue et al. proposed a light-weight scheme based on temporal credential. However, from Jiang et al.'s scheme [6] we can see that Xue et al.'s scheme is vulnerable to identity guessing attack, tracking attack, smart card lost attack and privileged-insider attack. For solving these problems, Jiang et al. proposed a two-factor user authentication scheme for WSNs. Owing to the attractive advantages in biometric, a lot of biometric-based or three-factor user authentication schemes for WSNs have been proposed [8][9][10][11][12]. In 2014, Das proposed three-factor authentication scheme [8] and pointed out that there are several drawbacks. For example, Jiang et al.'s scheme may suffer insider attack and be hard to use. In 2013, Althobaiti et al. [10] proposed an authentication scheme for WSNs based on biometrics. Althobaiti et al.'s scheme is efficient in computation. However, Das [11] pointed out that Althobaiti et al.'s scheme could not resist node capture attack, impersonation attack and man-in-the-middle attack. Recently, Das proposed a secure and efficient threefactor authentication protocol for the WSNs [12] in January of 2015.This scheme has a lot of advantages such as light-weight. However, with a careful research, we also find quite a few problems in his scheme. In order to solve these problems in Das's scheme [12], a new threefactor authentication scheme for the WSNs is proposed in this paper.

The weaknesses of the das's scheme
There are some advantages in the Das's scheme just like light-weight and dealing with biometric reasonably. However, the scheme needs to be improved after our careful analysis. In this section, we present four flaws in the Das's protocol. The details of these attacks are shown as follows. The scheme has some design flaws: 1) In the authentication and key agreement phase of Das's scheme, the BS cannot get the value of 4 M by computing () is h ID X because the BS cannot obtain the information of i ID . Firstly, i ID cann't be sent to the BS and the BS doesn't store also during the authentication and key agreement phase. From the analysis, we can see that the scheme proposed by Das is not effective. 2) The scheme is vulnerable to sensor node impersonation attack: It is generally known that all the sensor nodes are not equipped with tamper resistant hardware. The attacker can acquire all the information stored in sensor node by side channel attack. In the Das session key may be revealed by attacker. 4)The Scheme cannot Achieve the Identity of Sensor Node Anonymously: Sometimes, the identity that which sensor node is being visited may leak important information especially in military and healthcare applications. So the proposed scheme must protect the identity of sensor nodes which the user needs to access. In the Das's scheme, the user sends

The proposed scheme
In this section, a new scheme based on secure sketch is proposed to overcome the problems of the Das's scheme. There are five phases in this scheme: a) initialization, b) registration, c) login and authentication, d) password change and biometric update phase, e) dynamic node addition phase. In order to describe and analyze our scheme better, we use as possible same as notations used in the Das's scheme. We introduce the notations in Table 1.

Initialization Phase
In this phase, there are some necessary preparatory works as following steps:1)The BS generates Kpub_key and Kpri_key by the public key algorithm such as ECC (Elliptic Curve Cryptography).
2)The BS generates a 1024-bit random master key Xs. The BS must assure the value of Kpri_key and Xs absolute safety.
3)The BS assigns a unique identity IDSNj for i I D each deployed sensor; 4) The BS writes IDSNj and Kpub_key into the memory of each deployed sensor node. 5)Then, SNj can be deployed in the target field according to the steps in the reference [13].

Registration phase
If i U wants to become a legal user in WSNs, he must register with the BS according to the

Login and authentication phase
In this phase, if one registered user wants to acquire real-time data from any sensor nodes inside WSNs, he must execute the following steps: Then, Ui can communicate with SNj by encrypting information with the key _S U K . The details are shown in Figure 3.

Password and biometric update phase
Sometimes, user needs to change his password or biometric in WSNs. In our scheme, user can alter his password or biometric arbitrarily without contacting the BS. This phase involves the following steps:1) Ui provides his/her old password

Security analysis of the proposed scheme 4.1 Formal security validation using ProVerif
In this section, we prove the security of our proposed scheme using ProVerif which is automated formal tool. ProVerif is based on applied calculus and can be used to verify authentication and secrecy properties. There are three parts in the ProVerif : (1) declaration part; (2) process part; (3) main part. The ProVerif code for the definition of functions, reduction, equation, free names and constants is as follows. We perform the above process in the online demo for ProVerif (http://proverif.rocq.inria.fr/index.php). The performance results as shown in the Fig 4. From the experimental results, we can see that our proposed scheme is security. Fig. 4. The performance resul.

Security analysis
In this section, our scheme presents how various known attacks can be resisted.

Repeat registered Attack
In the proposed scheme, the user can select his/her identity randomly. So there is a case that different people may select the same identity. However, our scheme can overcome this problem. At first, the attacker cannot select other people's identity in the required time interval. After the time interval, the registration time is not the same, so the attacker can get different value of (

Three-factor security
In our scheme, a user must provide {password, smart card, biometric} in order to obtain legal identity. Even the attacker acquires the password of any one of them, he cannot acquire biometric from it or other information stored in smart card. The user cannot acquire , reg ii pw B from (pw ) i h because of the collision-resistant property of h(.). From the analysis, we can see that a user can finish authentication successfully only when he provides all the following information {password, smart card, biometric}. So our proposed scheme can achieve three factors. All the security properties between the proposed scheme and Das's scheme have been compared in Table 2.

Performance Analysis
The capability of our proposed scheme will be compared with that of the Das's in this section. For convenience, some notations are defined as described below.
x T :the time for executing an XOR operation; h T : the time for executing MD5 operation; s T : the time for executing a symmetric decryption/encryption operation;TPE: the time for that our scheme has higher security and a lower computation cost than the Das's at client in spite of a slight higher computation cost in the BS and the sensor node.