Distributed Secure Routing Protocol for Mobile Ad-Hoc Networks Issa Khalil1, Sameer Bataineh1, Liana Qubajah2 and Abdallah Khreishah3 1: Faculty of Information Technology, United Arab Emirates University, UAE, E-mails: {ikhalil;samir.b}@uaeu.ac.ae 2: Computer Science and Information Technology Faculty, University of Malaya, Malaysia,
[email protected] 3: Electrical & Computer Engineering, New Jersey Institute of Technology, USA, E-mail:
[email protected] Abstract—Mobile Ad-Hoc Networks (MANETs) reputation is ever increasing rapidly. With the wide spread of MANET the need for securing routing protocols emerges as a very important issue, which is not easy to achieve in MANET. The concept and structure of MANETs make them prone to be easily attacked using several techniques often used against wired networks as well as new methods that have been particularly developed for MANETs. In this paper, we have focused, in particular, on the security issues related to Ad-Hoc routing protocols. A new protocol, based on Authenticated Routing for Ad-Hoc Networks (ARAN) Protocol and Zone Routing Protocol (ZRP) is proposed. The proposed Authenticated Routing for Ad-Hoc Networks with zoning (ARANz) introduces a distributive nature routing algorithm, which improves performance of routing protocol by dividing the area into zones. ARANz also saves network bandwidth and nodes memory by using reactive routing protocol instead of proactive one (ARAN). Furthermore, it increases network security by introducing local and global Certificate Authority servers.The performance of ARANz is compared to the two existing well known routing protocols: AODV and ARAN protocols. This comparison was done using GloMoSim simulator. The results show the superiority of our protocol in various aspects. Keywords- MANET; secure wireless networ; routing protocol;
I.
INTRODUCTION
Ad-Hoc wireless networks are self-organizing multi-hop wireless networks where all the hosts (or nodes) take part in the process of forwarding packets. Ad-Hoc networks can quickly and inexpensively be set up as needed since they do not require any fixed infrastructure, such as base stations or routers. Therefore, they are highly applicable in many fields, such as emergency deployments and community networking [1][2]. A key component of Ad-Hoc wireless network is an efficient routing protocol. All the nodes in the network act as routers and links. Ad-Hoc network routing protocols are difficult to design in general. There are two main reasons for that; first, the highly dynamic nature of the Ad-Hoc networks due to high mobility of the nodes [2-4]. Second, the need to operate efficiently with limited resources [4]. Many Ad-Hoc routing protocols that use reactive route determination have been developed. Some of these protocols are Dynamic Source Routing (DSR) protocols [1,5] and AdHoc On-demand Distance Vector (AODV) protocols [3,6]. The major problem of such protocols is that they do not define security requirements. They inherently trust all participants, though, they have security vulnerabilities and exposures that easily allow routing attacks [2]. With the ever increasing attractiveness of the Ad-Hoc networks, the issue of the security of the routing protocols of the Ad-Hoc networks has attracted many researchers in last decade [7-11][17]. Depending on the type of network environment, there are two main types of security-enhancing techniques have been
developed. One by enhancing the existing protocols such as the Enhanced Heading-direction Angle Routing Protocol (EHARP), which is an enhancement of HARP based on an ondemand routing scheme [12]. Another recent example is the Anonymous source routing, called SADSR (Secure and Anonymous Dynamic Source Routing) which is based on DSR [13]. The other way is by developing new ones from the ground up such as the Authenticated Routing for Ad-Hoc Networks (ARAN) and Secure Position Aided Ad-Hoc Routing (SPAAR) [2,4,14]. Security in the routing protocol is necessary in order to guard against attacks such as malicious routing misdirection. The existing insecure Ad-Hoc network routing protocols are optimized to broadcast new routing information quickly as conditions change. This requires more rapid and frequent interaction between nodes than what is typical in a wired and stationary network. Introducing security mechanisms into routing protocols can both be expensive and cumbersome as they can incur delays or prevent such exchanges of routing information, leading to a reduction in routing effectiveness. Moreover, they may consume excessive network or node resources [15]. A good recent attempt to develop an efficient but yet secure routing protocol for AdHoc network with mobility that reduces the control packets in a highly dynamic environment can be found in [16] . Though ARAN provides security and authentication, it fails when its server is compromised. The SPAAR achieves a reasonable level of security, but it suffers from the compromised server problem, high overhead and the need for extra hardware (GPS). The new proposed protocol has high authentication as in ARAN, and deals with the network as zones to avoid compromising the server. Also, the proposed model overcomes the single point of failure by installing multiple Certificate Authorities (CAs) in the same zone so that any node in the zone can take the certificate from one of these CAs, which saves the network bandwidth and nodes memory by using reactive routing protocol instead of proactive one and increases the network security by introducing Local and Global CAs (LCAs and GCAs). Moreover, the distributive nature of the algorithm enhances security without compromising the efficiency. The rest of the paper is organized as follows; section 2 discuses the model of the system. In Section 3, the new protocol Authenticated Routing for Ad-Hoc Networks with zoning (ARANz) is introduced. The main results are discussed in section 4. A concluding remarks and future work are found in the last section. II.
SYSTEM MODELING
We assume N nodes in a managed-open environment. These nodes are distributed randomly in an area of (K) Km2 area. This area is divided into Z zones; the area of each zone is 1
(K)/Z Km2. Nodes in each zone communicate using ARAN protocol and nodes in different zones use the communication strategy proposed in section III. There are 4 permanent trusted LCAs in each zone located at the boundaries of the zone and carry identical information in order to provide a backup and avoid single point of failure. The public keys of these LCAs are made available to other nodes in zone. Note that our protocol will also work for the case of static sensor network, however, we need to use lighter cryptographic primitives such as SECOS [18] and wireless reprogramming capabilities [19]. Before entering the Ad-Hoc network, each node must request a certificate from one of the LCAs in the zone it intends to enter. Moreover, nodes in each zone should update its certificate when it is expired. Before granting a certificate to a node, the LCA must authenticate the node identity. This process is beyond the scope of our research. However, this can be easily done through a MAC address and/or IP address as we are dealing with managed-open environment. Also, each LCA has an authentication table that contains a tuple for each node. At the beginning, this table contains the MAC address and/or IP address for each node in that particular zone. This table will be used by the LCAs to authenticate the nodes identity before granting them their certificates. After issuing a certificate to a node, the corresponding tuple is completed by adding public key, time stamp, and certificate expiration date for that particular node. This table is used when a route discovery is needed; LCA checks whether the destination of the route is local or external one in order to drop it or resend it to other zones respectively. There are 4 permanent trusted GCAs in the whole area. The public keys of these GCAs are known to LCAs. These GCAs are located at the boundaries of the global area, and carry identical information in order to act as a backup in case of a node malfunctioning. This will also alleviate the single point of failure problem. Before entering the Ad-Hoc network, each LCA must request a certificate from one of the GCAs. Each GCA has an authentication table that contains a tuple for each LCA. Each tuple contains the IP address, public key, time stamp, and expire date for that particular node. The new model is shown in Fig. 1.
Fig. 1: System Modeling. In order to bring our model very close, if not identical, to the implemented real life practical systems, each node (except CAs) can use the LCAs to depart to another zone. The departing node sends a message to the suitable LCA (the nearest LCA to the new zone), which, in turn, sends two messages. The first message is sent to the neighbor LCA in the
next zone. This message indicates that this node is trusted and it can be granted a certificate. The second message is sent to the departing node and contains the public key of the LCA in the new zone. III.
AUTHENTICATED ROUTING FOR AD-HOC NETWORKS WITH ZONING (ARANZ)
Let us start by defining the following variables and notations that will be used in this section and thereafter: TABLE I. KA+ KA{d}KA+ [d]KACertA NA
VARIABLES AND NOTATIONS FOR ARANZ PROTOCOL. Public key of node A Private key of node A Data d encrypted with key KA+ Data d digitally signed by node A Node A Certificate. Nonce issued by node A
IPA t e RDP REP ERR
IP address of node A Timestamp Certificate expiration time Route Discovery Packet identifier REPly packet identifier ERRor packet identifier
ARANz requires the existence of 4 LCAs in each zone. Before entering the Ad-Hoc network, each node must request a certificate from one of the LCAs in its zone. These LCAs are arranged as a queue, and once a LCA issues a certificate, it will become at the end of the queue. This strategy guarantees that a joining node will not get more than one certificate. Moreover, it will minimize traffic in the network, and save time of other LCAs. The LCA issuing a certificate will unicasts it to other LCAs in order to have identical information. In the case that one of the LCAs fails, it is removed from the queue, until it is repaired. LCA failure can be discovered when a new node joins the network and the other LCAs do not receive a message containing the new issued certificate. In this case, the next LCA in the queue issues a certificate to the new node, and the queue is treated if it contains only 3 servers. When the failed LCA is repaired it sends messages to other LCAs in order to be added again to the queue. Each node receives exactly one certificate after securely authenticating its identity to one of the LCAs in its zone. The secure authentication is done using the authentication table that the LCA has; by searching for the MAC address and/or the IP address of the new node. A node A, for example, receives a certificate from LCA1 as follows: CertA =[IPA, KA+,ta,ea]K(LCA1) – The certificate contains the IP address of A, the public key of A, a timestamp ta when the certificate was created, and a time ea at which the certificate expires. These variables are concatenated and signed by LCA1. All nodes must maintain valid certificates with the trusted LCAs. Nodes use these certificates to authenticate themselves to other nodes during the exchange of routing messages. Before entering the Ad-Hoc network, each LCA must request a certificate from one of the GCAs. The GCAs are arranged as a queue, and work using the same strategy as the LCAs. A server LCA1, for example, receives a certificate from GCA1 as follows: Cert(LCA1) =[IP(LCA1), K(LCA1) +,tl1,el1]K(GCA1) The certificate contains the IP address of LCA1, the public key of LCA1, a timestamp tl1 when the certificate was created, and a time el1 at which the certificate expires. These variables are concatenated and signed by GCA1. All LCAs nodes must maintain fresh certificates. LCAs use these 2
certificates to authenticate themselves to other LCAs in the other zones during the exchange of routing messages. A. Authentication Route Discovery and Setup This subsection explains strategies for local and external route discovery and setup.
Authenticated Route Discovery/Setup between Two Nodes in the Same Zone
Each node that will participate in the route must have a certificate from one of the LCAs in its zone. For example: CertA =[IPA, KA+,ta,ea]K(LCA1) Source node begins route instantiation to destination by broadcasting to its neighbors a Route Discovery Packet (RDP). Abrdcast:[RDP, IPX, CertA, NA, t]KAEach node along the path validates the previous node’s signature (using the previous node’s public key, which is extracted from its certificate), removes the previous node’s certificate and signature, records the previous node’s IP address, signs the original contents of the message, appends its own certificate, and forwards the broadcast message. Bbrdcast:[[RDP, IPX, CertA, NA, t]KA-]KB-, CertB These steps are repeated until message is received by destination which also verifies the source signature and unicasts a REPly Packet (REP) back along the reverse path to source. XD: [REP, IPA, CertX, NA, t] KXEach node along the reverse path validates the previous nodes signature, removes the previous node’s certificate and signature, signs the original contents of the message, appends its own certificate, and forwards the REP packet back to the predecessor from which it received the original RPD. DC: [[REP, IPA, CertX, NA, t] KX-] KD-, CertD To stop broadcasting the RDP to other zones, when RDP reaches a LCA it checks the packet and finds that the destination is inside its zone so it drops the packet, unless the packet is for that LCA.
Authenticated Route Discovery/Setup between Two Nodes in Different Zones
Each node that will participate in the route must have a certificate from one of the LCAs in its zone, and each LCA must have a certificate from one of the GCAs. Source node begins route instantiation to destination by broadcasting to its neighbors a RDP packet. Each node along the path (except CAs) validates the previous nods signature, removes the previous node’s certificate and signature, records the previous node’s IP address, signs the original contents of the message, appends its own certificate and forwards the broadcast message. These steps continue until reaching a LCA. Each LCA receives a message from inside its zone will drop this packet, if the destination of the packet is inside its zone. Else, LCA will act as any intermediate node; i.e. it validates the previous node’s signature, removes the previous node’s certificate and signature, records the previous node’s IP address, signs the original contents of the message and appends its own certificate. Then instead of broadcasting the message, LCA will unicast it to the LCA beside it in the
following zone, so that LCA of the next zone can validate its signature, and broadcast it to other nodes in its zone. Each LCA receives a message from outside its zone will drop the packet, if the last node was not the LCA of previous zone. Else it will act as any intermediate node; i.e. it validates the previous node’s signature, removes the previous node’s certificate and signature, records the previous node’s IP address, signs the original contents of the message, appends its own certificate, and forwards the broadcast message. When message is received by destination, it unicasts a REP packet back along the reverse path to source, so steps 2 through 6 are repeated with considering source as destination and vice versa.
B. Route Maintenance ARANz is an on-demand routing protocol; nodes keep track of whether routes are active or not. When no traffic has occurred on an existing route for that route’s lifetime, the route is simply deactivated in the route table. As in ARAN [2], nodes use ERRor (ERR) messages in two cases:
Data received on an inactive route. To report links in active routes that are broken due to a node movement.
These ERR message travels the reverse path toward the source. All ERR messages must be signed. For a route between source A and destination X, a node B generates the ERR message for its neighbor C as follows: BC:[ERR, IPA, IPX, CertB, NB, t]KBThis message is forwarded along the path toward the source without modification. A nonce and timestamp ensure that the ERR message is fresh. It is extremely difficult to detect when ERR messages are fabricated for links that are truly active and not broken. However, because messages are signed, malicious nodes cannot generate ERR messages for other nodes. C. Responses to Erratic Behavior Erratic behavior includes the use of invalid certificates, improperly signed messages, and misuse of route error messages. Erratic behavior can come from a malicious node or from a friendly node that is malfunctioning [2]. ARANz’s response does not differentiate between the two and drops all the packets that have erratic behavior. D. Key Revocation Public key should be revoked if the owner node is no longer trusted or is out of network. Due to the desired low-overhead in wireless networks a best-effort immediate revocation service can be provided [2]. In the event that a certificate needs to be revoked from a node that is no longer trusted, the LCA or the GCA that originally issued the certificate to that node sends a broadcast message to tell other nodes about this revocation. For example if LCA1 wants to revoke the certification from node R, this is done by broadcasting the following message: LCA1brdcast:[Revoke, CertR]K(LCA1) Any node receiving this message re-broadcasts it to its neighbors. Revocation notices need to be stored until the revoked certificate would have expired normally. Any neighbor of the node with the revoked certificate needs to reform routing 3
RESULTS AND PERFORMANCE ANALYSIS
To study the effect of the node mobility speed, a 2km×2km network was considered. This network contains 240 nodes (i.e. node density of 60nodes/ Km2) and divided into 4 zones. Simulations were run with 0m/sec, 3m/sec, 5m/sec, and 10m/sec speeds. Five CBR sessions were simulated in each run three of them are local and two are external. As shown in Fig. 3, Packet Delivery Function (PDF) obtained using ARANz protocol is above 95% in all scenarios. This suggests that ARANz is highly effective in discovering and maintaining routes for delivery of data packets even with relatively high node mobility. As we can see also from the Fig. 3, PDF for ARANz is identical to that for ARAN and AODV in the low node mobility, but it’s slightly less when mobility increases. This is due to the longer paths that packets take in the external communication because ARANz forces the packets to pass through CAs. In other words, longer paths means longer time and higher probability for losing the link connection due to node movement, which results in dropping some packets. 1.05
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Fig 3: Packet Delivery Fraction.
Fig. 4 shows that ARANz has the minimum Packet Routing (PRL. ARANz does not broadcast the RDP to whole area in the case of local communication; this is why the overall PRL is reduced. It also shows that PRL for the three protocols increase with increasing node mobility. This is because increasing mobility will increase the chance for losing the link connection and reinitiating RDP which increases overall PRL for AODV. 0.5
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IV.
Although ARANz has smaller PRL than AODV, Fig. 5 shows that it has higher BRL due to the larger ARANz control packet that contains security data. This results in significantly larger control bytes for ARANz as number of intermediate nodes increases. The figure also shows that, as with PRL, increasing node mobility will increase BRL due to loosing links and reinitiating RDPs.
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Fig 5: Routing Load in Bytes.
ARANz does not explicitly seek shortest paths; however, the first RDP to reach the destination usually travels along the shortest path in local communication (As shown in Fig. 6). For external communication, the first RDP travels along a slightly longer path because ARANz forces the packet to pass through CAs. This explains the slight difference, in Fig. 6, in APL between ARANz and other two protocols in the high node mobility, since most communication will become external ones. In other words, with high node mobility the chance for nodes to leave and enter zones in increased. This increase the percentage of external communications in which RDP are forced to pass through the CAs, which results in slightly longer paths. ARAN and AODV APL increases with increasing node mobility but in slower rate than ARANz. This is because both protocols do not force RDPs to pass through CAs. Also it is obvious that ARAN is as efficient as AODV in discovering shortest paths. 10 ARAN-Z ARAN AODV
9 8
Average Path Length (hop)
as necessary to avoid transmission through the node that becomes untrusted
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Fig. 6: Average Path Length.
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Fig. 4: Routing Load in Packets.
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Fig. 7 shows that Average Route Acquisition Latency (ARAL) for ARANz is approximately double that for AODV. While processing ARANz routing control packets, each node has to verify the digital signature of the previous node, and then replace this with its own digital signature, in addition to the normal packet processing as done by AODV. This signature generation and verification causes additional 4
delay at each hop, and so ARAL increases. Also, Fig 7 shows that ARAL for ARANz is less than that for ARAN with low node mobility, and nearly identical with relatively high node mobility. With low node mobility, the chance for the nodes to stay at the same zone is high. This shows the efficiency of ARANz in local communication, since RDP is not broadcasted outside the corresponding zone. However, in ARAN the RDP will be flooded to the whole area even if communication is locally. This flooding affects ARAL for the other external communication, since processing this RDP in a node outside this zone will cause more delay for other RDPs that comes while processing this RDP. On the other hand, when the node mobility becomes higher, nodes will leave and enter zones in higher rate, which will make ARANz becomes nearly the same as ARAN in terms of flooding the whole area with the RDP, so the local communications dwindle and becomes insignificant and most communications will become external ones 200
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Fig. 7: Average Route Acquisition Latency.
CONCLUSION AND FUTURE WORK In this paper we have developed a new routing protocol that provides an efficient solution for secure routing in the managed-open environment. This protocol introduces a set of features such as distributive nature routing algorithm, dividing the area into zones, using reactive routing protocol, overcoming the compromise server problem and single point of failure, and introducing local and global certificate servers. GloMoSim simulator has been used to study the performance of the new model and compare it with AODV and ARAN protocols. Simulation results showed that the new proposed protocol, ARANz, is highly effective in discovering and maintaining routes even with relatively high node mobility, large area networks, or large percentage of malicious nodes. Also, ARANz has the minimum PRL in all experiments. As an extension of our work, we are in the process to introducing GPS into our protocols. Also we are trying to make the system more flexible by allowing the nodes to move freely REFERENCES [1] D. Lundberg, “Ad-Hoc Protocol Evaluation And Experiences of Real World Ad-Hoc Networking,” Department of IT, Uppsala University http://www.update.uu.se/~davidl/msthesis/thesis.pdf [2] K. Sanzgiri, B. Dahill, B. N. Levine, C. Shields, E. M. Belding-Royer, "A Secure Routing Protocol for Ad Hoc Networks," 10th IEEE International Conference on
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