Security and Dynamic Encryption System in Mobile Ad-Hoc Network
Peter H., Udo W. · InTech eBooks · 2011
Wireless network technology enables computing devices to communicate with each other without any physical medium.Compared with wired networks, wireless communication provides better connectivity and mobility, which allows mobile devices to access other local area networks or the Internet at anytime and anywhere.The benefits of flexible routing, global connectivity and a highly adaptive potential make mobile ad-hoc networks (MANET) suitable for a wide range of applications in both military and commercial environments, such as battlefields, disaster relief operations, mobile device/ personal networking, mobile information sharing and vehicular networks (Kant et al., 2005); (Liu et al., 2007).However, maintaining security in wireless ad-hoc networks is quite challenging.First, unlike wired networks that at least have some degree of physical protection, wireless communication over radio waves lacks defined and restricted boundaries.Anyone can connect to the network as long as the transmitted signal strength is strong enough to cover the area (Chan et al., 2005), and therefore, security attacks on data communication, such as passive eavesdropping, packet injection or even violations of confidentiality are widespread.Second, the end-to-end communication in MANET cannot rely on any fixed infrastructure, such as a base station or access points (AP); thus, existing security protocols that are based on a centralized or infrastructure-based network environment will not work in this mobile environment (Hubaux et al., 2001).Third, in order to achieve better network throughput in such a highly dynamic environment, the default routing protocol does not implement any security protection during end-to-end communication.In addition, the trust relationships between each node are very low as a consequence of the frequently changing topology and membership.Because of this, many attacks can be launched against the routing protocol, giving hackers a major opportunity to insert themselves as one of the cooperative nodes in the network.Therefore, the security protection that is used to ensure the integrity of the mobile ad-hoc network should not only repel external attacks, but also prevent internal attacks launched against the network from any compromised node.Most security mechanisms rely on data encryption, which is a message combined with a secret key to generate a ciphertext that cannot be revived without the original key.This encryption mechanism can prevent any unauthorized user from gaining access to the secured communication.However, a fixed secret key is vulnerable to deciphering by www.intechopen.comMobile Ad-Hoc Networks: Protocol Design 470 capturing sufficient packets or by launching a dictionary attack.Therefore, the most efficient way to protect the network from such attacks is to generate the secret key dynamically and replace it periodically (Ramakrishnan et al., 2005).Furthermore, the protocol applied to the mobile ad-hoc wireless network should be sufficiently flexible to adjust to different levels of security protection to fit the needs of applications in different environments and with varied communication speeds.For example, mobile banking and E-commerce require larger encryption keys for stronger protection, while real-time driven applications such as disaster recovery, stream services like VOIP and online video need to preserve data privacy as well as performance to maintain the quality of services (QoS).In this chapter, we introduced a new, efficient, low-bandwidth cost and security-enhancing data encryption i-key protocol for mobile ad-hoc wireless networks via dynamic re-keying during end-to-end communication.Unlike its counterparts, this secret i-key is generated using the previous data as the seed and as next packet encryption before delivery; therefore, only the original sender and authorized client are able to decrypt the message using the unique i-key in their possession, which ensures the privacy of their communication. Related workWired Equivalent Privacy, or WEP, is an encryption protocol designed by the IEEE 802.11 and Home RF group (Lansford & Bahl, 2000) in an attempt to protect link-level data over radio signals for wireless networks, included both Base Station (BS)-oriented and mobile adhoc networks, to the security level closer to wired one.The WEP key used to encrypt data sent over wireless networks consists of two parts: the Initialization Vector (IV) and user preshared secret key (PSK).The stream cipher, RC4 used in WEP, expands the IV (40 or 104 bits) and PSK into an arbitrary long "key stream" of pseudorandom bits then XOR with the plaintext to obtain the ciphertext.To decrypt it, the receiver side takes the same steps in the reverse order by the same key stream.In addition, a CRC-32 algorithm is applied to check the data integrity for each data packet in WEP encryption.Many WEP vulnerabilities and security design issues has been discovered and reported by researchers since the IEEE released it as the standard encryption protocol for 802.11