Detection of Sybil Attack for P2P Security in Manets

: A MANET is an infrastructure-less type networks, which consists of the number of mobile nodes with wireless network interfaces Sybil attack is a serious threat for today’s wireless adhoc networks. In this attack a single node pretends several other nodes using various malicious means. Here we considered Topology based routing protocols like DSDV and DSR for the detection of SYBIL attacks in P2P system. Performance metrics such as packet delivery fraction, throughput, and end-to-end delay are evaluated using NS-2.


THE SYBIL ATTACK
Malicious nodes in a network may not only impersonate one node, they could assume the identity of several nodes by doing so undermining the redundancy of many routing protocols. This attack is called the Sybil attack. Sybil attack manifests itself by faking multiple identities by pretending to be consisting of multiple nodes in the network. So one single node can assume the role of multiple nodes and can monitor or hamper multiple nodes at a time [3]. A consequence of this is that attackers have a harder time to destroy the integrity of information. If the same packet is sent over several distinct paths a change in the packets incoming from one of these paths can be detected easily. Thus, isolating a possible intruder in the network becomes possible.
However, if a single malicious node is able to represent several other nodes, the effectiveness of these Computer Engineering and Intelligent Systems www.iiste.org ISSN 2222-1719 (Paper) ISSN 2222-2863 (Online) Vol. 6, No.5, 2015 78 measures is significantly degraded. The attacker may get access to all pieces of the fragmented information or may alter all packets in the same transmission, so that the destination node cannot detect tampering anymore. The Sybil attack is especially aimed at distributed system environments. The attacker tries to act as several different identities/nodes rather than one. This allows him to forge the result of a voting used for threshold security methods. Since ad hoc networks depend on the communication between nodes, many systems apply redundant algorithms to ensure that the data gets from source to destination. A consequence of this is that attackers have a harder time to destroy the integrity of information [2]. To disturb network topology, adversary often changes the locations with different legitimate node ids. To disturb multi-path routing, the attacker appears with multiple identities in the network, which are taken from the compromised node and appearing in most of the node disjoint paths.
A Sybil node may fabricate a new identity for itself or it steals an identity of the legitimate node. Various effects due to the presence of Sybil attacks are: • In the presence of Sybil nodes in the network, it may make difficult to identify a misbehaving node.
• Sybil attacks, prevent fair resource allocation among the nodes in the network.
• In certain application, sensors can be used to perform voting for decision making. Due to presence of duplicate identities the outcome of voting process may vary. • Sybil nodes affect the normal operation of routing protocols by appearing itself at various locations in network [4].

EXPERIMENTAL RESULTS AND DISCUSSION
Throughput: It is one of the dimensional parameters of the network, which gives the fraction of the channel capacity used for useful transmission selects a destination at the beginning of the simulation In this graph Figure  5.1 after the detection of Sybil attack the throughput get increased than before Throughput =N/1000 Packet delivery ratio: It is defined as the ratio of data packets received by the destinations to those generated from the sources. The Graphs show the fraction of data packets that are successfully delivered during simulation time versus the number of nodes. In the below graph Figure 5.2 delivery ratio has increased when the packets delivered without Sybil attack when compared to packet delivery with Sybil attacks.

Figure: 5.2 Packet Delivery Fraction with and without Sybil attack
Packet loss is the discarding of packets in a network when a router or other network device is overloaded and cannot accept additional packets at a given moment. In the below analysis Figure 5.3 the packet drop becomes high when a Sybil attack is detected. Later after removal of Sybil attack, we found that packet drop has decreased.

CONCLUSION
The research on MANET security is still in its early stage. In this paper, we have analyzed the security threats an ad-hoc network faces and presented the security objective that need to be achieved.In this paper, a survey on detection and prevention techniques Sybil attack in MANET ispresented.Mainly this involves detection of SYBIL attack where a malicious node do not forward the data packets to the destination and causes serious threat for Wireless MANETS. This paper focused on the discovery of topology in MANETS using routing protocols DSDV and DSR with NS2 simulator using RSS detection algorithm.In addition to this various factors affecting the detection accuracy, a loss of packet rate is also shown. This includes mainly improving throughput and packet delivery ratio with security in the network in addition with detection of Sybil attacks. Also packet delivery fraction has tackled with and without Sybil attacks in the network.

FUTURE WORK:
The future work can include more efficiency and security without Sybil attack in the network which gives better packet delivery rate and other tackling issues related to variable transmit powers and masquerading attacks in the network.