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Orthogonal Code Based Anonymity Communication Protocol for Wireless Sensor Networks [Sensors & Transducers (Canada)](Sensors & Transducers (Canada) Via Acquire Media NewsEdge) Abstract: In some environments, the security of the wireless sensor networks (WSNs) involves not only the security of sending data, but also the anonymity and privacy during data delivery, how to design a secure efficient anonymity communication scheme for wireless sensor networks has became an important research topic. The proposed schemes can provide efficient anonymous communication, but some of the schemes need more overheads on computation, storage and bandwidth consumption. In this paper, an anonymous secure communication protocol for wireless sensor network is proposed based on orthogonal code and symmetric secret key, comparing with the previous anonymous communication schemes for wireless sensor networks, this scheme not only can satisfy the basis require of anonymity communication, but also improve distinctly in storage and bandwidth consumption, and is more suitable for the wireless sensor networks. Copyright © 2014 IFSA Publishing, S. L. Keywords: Wireless sensor networks, Anonymous communication, Orthogonal code, Anonymity, Bandwidth consumption. (ProQuest: ... denotes formulae omitted.) 1. Introduction With the development of more advanced sensor technology, wireless sensor networks are widely used in various fields, such as health care [1], military, environmental, target tracking [2], etc. Wireless sensor network is composed by many low-cost sensors, the computing and storage capacity of each sensor node is limited. Sometimes, wireless sensor network is deployed in unprotected or hostile environment, and it is vulnerable to be attacked by the adversary. The security of WSNs is not only involved in the confidentiality, integrity and authentication of the communication content, but also the anonymity and privacy during data delivery. The adversary can locate and compromise some important nodes by eavesdropping on the identities of the communication nodes, and the adversary can launch many attacks through the compromised nodes. Therefore, an efficient anonymous communication scheme is essential for WSNs to hiding the real identities of communication nodes. Anonymous communication of WSNs is that the communication relationship between the sensor nodes is hidden by a certain method, and the eavesdropper can not know or infer the identity of any sensor node and the communication relations of both. In order to prevent the adversary from eavesdropping on the identities of the communication nodes, a variety of anonymous routing schemes were proposed for mobile ad hoc networks that are closely to wireless sensor networks [3-7], but the mobile ad hoc networks are different from the wireless sensor networks, and these schemes can not be applied straight to the resourceconstrained WSNs. Recently, there are some works on anonymous routing schemes for wireless sensor networks [8-12]. The proposed schemes can prevent the adversary form getting the identities of the communication, but some of the schemes need more overheads on computation, storage and bandwidth consumption. In this paper, an anonymous secure communication protocol for wireless sensor network is proposed based on orthogonal code and symmetric secret key. In our scheme, each sensor node is assigned to an orthogonal code as the unique identity, the Summation of all the identities of intermediate forwarding routing nodes is transmitted with the packet, according to the additive property of orthogonal code, any intermediate routing node in the routing path can confirm that it is part of the routing path, but do not know the real identities of the communication sender and receiver, and the destination node i do not know the real identities of the intermediate routing nodes also. This scheme not only can satisfy the basis require of anonymity communication, but also improve distinctly in storage and bandwidth consumption. The organization of the lecture is as follows. The related work is introduced in Section 2, in Section 3 briefly introduces The Orthogonal Code, the Section 4 is the description of anonymity communication protocol for wireless sensor networks, anonymity, security, and performance analysis of the new scheme are discussed in Section 5 and 6, Section 7 is the conclusion. 2. Related Work Recently, anonymity communication in wireless sensor has become an important topic, there are some anonymous routing schemes are proposed for wireless sensor networks. S. Misra and G. Xue [9] proposed an anonymous scheme (SAS) for clustered wireless sensor networks. To ensure concealment of its true identifier (ED), the SAS uses a range of pseudonyms as identifiers for a node in the network, and the ranges are non-contiguous and chosen uniformly at random from a pseudonym space. After deployment, neighboring nodes in the network share their individual pseudonyms and use them to ensure that the communication is anonymous and that a node's true ED is kept private. Even when many nodes in a given neighborhood of the network are compromised and are colluding, The SAS ensures that non-compromised nodes are still guaranteed complete anonymity. In [10], Yi Ouyang, et al. proposed two schemes for protecting anonymity of sensors in wireless sensor networks based on hash function chain, HIR and RHIR. The basic idea of HIR is for each individual sensor node to use a one-way keyed hash chain for producing a sequence of hash values as its IDs. The anonymity of a message's sender is protected as long as the key is not compromised. A sensor node can delete its previous ED and generate a new one after sending a message. In RHIR method, it uses a one-way hash chain in reverse-in other words, it assigns a sensor node's ID backwards from the end of the hash chain to the beginning. This change improves the security properties of HIR method. Both schemes can provide better anonymity than previous solutions when the secret keys are compromised. But two schemes require each node maintains a routing information table, with the increasing of number of nodes, it required storage space is increasing dramatically, and is not suitable for large-scale distributed wireless sensor networks. In [11], an efficient Anonymous Communication (AC) protocol for sensor networks was proposed. The AC protocol was composed by anonymous onehop communication and anonymous end-to-end communication scheme. In the protocol, each sensor node finds the link direction (towards the base station) between itself and its neighbors during the deployment stage by a broadcast from the base station. Then the sensed data can be sent to the base station hop-by-hop by the link direction. After that, the AC protocol utilizes an anonymous one-hop communication scheme and an anonymous end-to-end communication scheme to achieve the source anonymity, the communication relationship anonymity and the base station anonymity. In [8], to protect sources against the local adversary and global adversary, P. Pengjun and V. Boppana proposed an anonymous communication protocol for WSNs. In the protocol, Each node transmits exactly one fixed-size packet in an active period regardless of whether it has useful data to send/forward or not. Upon a reception of a real packet, a sensor node buffers it, processes it, and relays it when next transmission is fired. If a dummy packet is received, it is discarded immediately. If a sensor node has a real packet in its buffer (its own injected packet or a received relay packet) when next transmission is fired, it sends the packet immediately. If not, a dummy packet with the same size will be generated and sent. In the case when the sensor node has multiple real packets, data aggregation may be used to make sure only one packet is sent. In [12], a lightweight anonymous on-demand routing scheme (LANDER) was proposed, the LANDER first uses Bloom filter to hide the identities of the routing sensor nodes, and thereafter generates per-hop pseudo-link identifiers based on the elliptic curve cryptosystem for accomplishing private information exchange in WSNs. In the LANDER scheme, after path establishment, each pair of neighbor nodes authenticate each other anonymously, and establish a pseudo-link identifier with an associated pair-wise key. This pair-wise key and pseudo-link identifier are used for anonymous data forwarding. This scheme not only conceals the node and the link identities in data packets, but also helps to achieve traffic anonymity due to content analysis. 3. Preliminary 3.1. The Orthogonal Code Orthogonal code [13] is widely used in the field of wireless communications and information hiding [14-15]. The orthogonal code has the following three properties. 1) Any two dissimilar orthogonal codes do inner product computing, the result of the operation is zero. For example, if A and B are two distinct orthogonal code, then, A*B=0 2) One orthogonal code and itself do inner product computing, the result of the operation is one. For example, if A is an orthogonal code, then, A*A=1 3) The Orthogonal codes have the property of additive, the sum of K orthogonal codes remains the characteristics of (1), (2). For example, if there are four orthogonal codes A, B, C and D, the S is the sum value of the three orthogonal codes A, B and C, then, ... (i) ... (ii) It can be determined from the formula (i), the A is contained in S, and it can be determined from the formula (ii), the D is not included in S. 4. Description of Anonymity Communication Protocol for Wireless Sensor Networks 4.1. System Model and Notations The wireless sensor network consists of the base station and a large of sensor nodes. The base station is not resource constrained, and can not be compromised. The base station will receive sensed data sent from the sensor nodes, and send some security operation instructions to the sensor nodes. The base station saves the whole network topology information. Each sensor node i have a unique identity IDi, each sensor node i is preloaded a secret key Ki,BS shared with the base station. We assume that the adversary can eavesdrop on and analyze the package transmitted in the network, and get the identities of the communication nodes and their communication relationships. The adversary can locate and compromise some important nodes by the identities of the communication nodes, and launch many attacks through the compromised nodes. This paper defines anonymous communication to achieve the following objectives. 1) Identity confidentiality. Any intermediate routing nodes do not know the real identities of the communication sender (source) and receiver (destination), and the sender and the receiver do not know the real identities of the intermediate routing nodes also. 2) Position confidentiality. The location of the sender and the receiver will not be known by the other nodes, intermediate routing node can not get the distance between the source and destination, in other words, intermediate forwarding node can not judged to the hops from the sender to the receiver. 3) Routing anonymity. The adversary can not find the sender and the receiver by tracking sending packets, in other words, the third party is difficult to extrapolate the transfer mode of communication between the source and destination. Since many notations are used in our proposed protocol, in order to easy to inquire, compare and reference, we list the notations used in proposed protocol in Table 1. 4.2. System Initialization Each sensor node is preloaded a secret key Kißs shared with the base station. The system generates a series of mutually different orthogonal codes according to the paper [4], each sensor node is assigned to an orthogonal code as the unique identity IDi. The system deploys the sensor nodes to the target area. We consider only the static network, and it means that the sensor nodes can not move after deployment. 4.3. Anonymity Communication Protocol If the base station wants to communicate anonymously with the sensor node i, it will perform the following steps. 1) The base station selects a path from base station to node Si(BS, Si, S2,Si-, Si). 2) The base station computes the SumID = IDi © ID2 © ... © IDi-i © IDi, a communication sequence number RPID, and a timestamp T. 3) The base station generates the routing packet RP=< RPID||Sum!D|| EKi,Bs(data||T) >, and broadcast to the network, where the data denotes the security operation instruction is sent to the destination node i, and the Eici,Bs(data) denotes the data is encrypted by the secret key Kißs. 4) After receiving the routing packet RP, each node j will check if the packet has already been received using the unique RPID, if it has been in the memory, the packet will be dropped, if not, each node j will do inner product computing with it's IDj and SumID, L=SumID©IDj =(IDi © ID 2 © ... © IDi-i © ID;,) © IDj, if the result of the operation is zero, which means the node j is not in the routing path, it will drop the packet right now, if the result of the operation is one, which means the identity of the node j is contained in the SumID, in other words, the node j is in the routing path, it will saves the RPID to its memory, and attempts to decrypt the EKißs(data) with the secret key shared by the node j and the base station. If it can decrypt correctly the Eiüßs(data) and the timestamp T is within a reasonable range, the node j is the destination node, and anonymous communication is over, if can not, the node j is a intermediate routing node in the routing path, it will broadcast this packet to other nodes within its wireless transmission range. 5. Anonymity and Security Analysis 5.1. Anonymity Analysis 1) Identity confidentiality. In our scheme, each sensor node is assigned to an orthogonal code, as the unique identity IDi. All the identities of intermediate routing nodes are embedded in the SumID of the routing packet RP, any intermediate routing nodes do not know the real identities of the communication sender (source) and receiver (destination), and the destination node i do not know the real identities of the intermediate routing nodes also. 2) Position confidentiality. In our scheme, when the intermediate routing nodes receive the routing packet, each node j will do inner product computing with it's IDj and SumID, if the result of the operation is one, which means the node j is in the routing path, it can not get the distance from the source to destination, in other words, any intermediate forwarding node can not judged to the hops between the sender and the receiver. 3) Routing anonymity. All the identities of intermediate routing nodes are embedded in the SumID, only the nodes in the routing path can know itself is in the routing path, any other node or the adversary is difficult to extrapolate the transfer mode of communication between the source and destination. 5.2. Security Analysis 1) Against passive attack. The adversary can get the routing packet RP=< RPED||SumID|| EKißs(data|| T) >, but it has no the secret key shared between the node i and the base station, it can not get the data from the E«ißs(data). Although the adversary can get the SumID, but it has no any node identity in the routing path, it can not get any correct routing information. 2) Minimum information disclosure. The sensor node in the routing path only can confirm itself is in the routing path, it can get any routing information of other nodes. 3) Verifiability. Any intermediate routing node in the routing path can confirm that it is part of the routing path, because only the SumID and the node identity in routing path do inner product computing, the result of the operation is one. 6. The Performance Analysis 6.1. Storage Requirements In this section, we analysis the storage requirements of our scheme and the other schemes. We assume that the base station has unlimited computation ability and storage, we do not take the memory cost of the base station. In order to achieve the purpose of anonymous communication, in scheme [2], the amount of memory required by each node is 6 k + 7 kN, where k represents the size of the k-bits of the pseudo-name space, N is the number of the adjacent node of the current node, if there are 1000 sensor nodes in the wireless networks, the pseudo-name space is 64-bit, and the adjacent node of each node is 100, the amount of memory required by each node is 6*64+7*64*100=45184 bits~5.6 KB. In scheme [3], each node needs to maintain an information table of neighboring nodes. The table includes (HT, HHT(x), Link ), where HHT(x) denotes the keyed hash values of neighboring nodes' IDs, the HT denotes the number of hash operation and the Link denotes the direction of the data flow, the total storage requirement at each node is (HT+HHT(x)+Link)N, let k=128 bit, HHT(x)=k=128 bit, HT=k/2=64 bit, Link=k/2=64 bit and the number of neighboring nodes is 100, the amount of memory required by each node is (k+k/2+k/2)xN=100*(128+64+64)=25600 bits- -3.125 kB. In scheme [7], the total storage requirement at each node is 4k+3kN+2, where N denotes the average number of neighbors for each node, and k represents the size of the k-bits of the hashing value. For instance, in a WSN withlOOO nodes, let k=128 bit and each node has an average of 100 neighbors. The memory requirement shall be, 4*128+3*128*30+2=12,034 bits - 1.5 kB. For a WSN with 5,000 nodes and a neighbor size of 100 nodes, the memory requirement is: 4* 128+3 * 128*100+2=38,914 bits=4.8 kB. In our scheme, each immediate routing node needs to store the RPID to its memory for one anonymity communication. In order to save storage space, each node will delete all the RPID after period of time. The total storage requirement at each node is k/2*N during a period of time, where k represents the size of the k-bits of the RPID, N is the number of the RPID, if there are 100 RPID in each immediate routing node during a period of time, and let k=64 bit, the amount of memory required by each node is 64*100=6400 bit^0.78 kB. Table 2 compares the storage costs of our scheme with several existing anonymous communication protocols [2, 3, 7]. Table 2 shows that our scheme needs little memory burden. 6.2. Bandwidth Consumption In this section, we analyze the bandwidth consumption of our scheme and the other schemes. Let Lrpid, LsumiD denote the length of the RPID and SumID, and Le denotes the length of the data by encrypted. The format of the report packet is RP=< RPID||SumID|| EKi,Bs(data|| T) >, so, the length of a report packet is Lp= Lrpid+ LsumiD + Le. In scheme [3], the message that a sensor node received and sent is M= Ha} (ID) II EtadD) 11*11/),, where IDj means the identity of node j, the IDi means the identity of node i, the (ID) means using Kÿ as a key to hash IDj for HTj times, the IÍJID) means using Ki as a key to hash IDi for t times, the Dt is a encrypted data block collected by the sender. Let Lhi, Lh2 denote the length of the H^dD) and HkJID), let Lt denote the length of the t, and Ld denotes the length of Dt, so, the length of a report packet is Lp'= Lhi+ Lh2 + Lt + Ld. In scheme [7], the message that a sensor node received and sent is M=OHAIij11Ekij(Alt11 Eki(D)| |AAIÿ) + AAIÿ ||Drand, where OHAIÿ means One-hop anonymous identity shared between node i and node j, AIi means the global anonymous identity of node i shared between i and the base station, AAIÿ means an anonymous acknowledgement identity shared between node i and node j, Drand means an anonymous acknowledgement identity shared between node i and node j, and Ekÿ(D) means Data D encrypted by pair-wise key k. Let Lohai, Laai denote the length of the OHAIÿ and AAIÿ, Let Lorand, Le denote the length of the Ekij(AIi|| Eki(D)||AAIÿ) and Drand, so, the length of a report packet is Lp Lohai + Laai + Le' + LorandLet er, e$, denote the energy consumption of receiving and sending 1 byte report packet, when a intermediate routing node receives a report packet from another node, it will forward the report packet to the other nodes, so, the energy consumption in our scheme is Ep=n* Lp *(er+es), the energy consumption in scheme [3] is Ep'=n* Lp' *(er+es), the energy consumption in scheme [7] is Ep"=n* Lp" *(er+es), where n denotes the average number of hops from the source node to the destination node. Let er=12.5 pJ, es=16.25 pJ, Lrhd=64 Bits, LsumiD = 64 Bits, Lhi = Lh2 = Lohai =128 bit, Lt = Laai = LDrand =64 bits, Le = LD = Le' =24 Bytes, the figure 1 depicts the bandwidth consumption of our scheme, scheme [3] and scheme [7]. The Fig. 1 shows that our scheme is lower in energy consumption than scheme [3] and scheme [7] with the increasing of the number of hop from the source to destination. 7. Conclusions In this paper, we proposed a novel security anonymity communication scheme for wireless sensor networks based on orthogonal code and symmetric secret key. All the identities of intermediate routing nodes are embedded in the SumID, any intermediate routing node in the routing path can confirm that it is part of the routing path, but do not know the real identities of the communication sender and receiver, and the destination node i do not know the real identities of the intermediate routing nodes also. The anonymity, security and performance analysis show that our scheme not only can satisfy the basis require of anonymity communication, but also improve distinctly in storage and bandwidth consumption, and is more suitable for the wireless sensor network. 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H., Zero-Collision RFID Tags identification based on CDMA, in Proceedings of the Fifth International Conference on Information Assurance and Security, Xi'an, China, 2009, pp. 513-516. 1 Jiangang Deng,2 Zhiming Zhang 1 Science and Technology Research Place, Jiangxi Normal University, Jiangxi, Nanchang, 330022, China 2 School of Software, Jiangxi Normal University, Jiangxi, Nanchang, 330022, China 1 E-mail: [email protected] Received: 11 April 2014 /Accepted: 30 May 2014 /Published: 30 June 2014 (c) 2014 IFSA Publishing, S.L. |