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EBSCO Publishing : eBook Collection (EBSCOhost) - printed on 2/16/2016 3:46 AM via CGC-GROUP OF COLLEGES (GHARUAN) AN: 340572 ; Beyah, Raheem, Corbett, Cherita, McNair, Janise.; Security in Ad Hoc and Sensor Networks Account: ns224671
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8 A. Naveed and S. Kanhere the entire network is compromised. Therefore, the secret key needs to be changed frequently in order to ensure the appropriate level of security. Wired Equivalent Privacy (WEP) protocol: the security mechanism ini- tially employed by the IEEE 802.11i standard for WLAN security 4 is pre- dominantly based on the symmetric cryptographic technique. In addition to the issues identified above, a number of additional security issues have been identified. We do not go into details of these issues here. Interested readers are referred to the related publications. 20–22 4.2. Asymmetric Cryptographic Techniques Asymmetric cryptographic solutions involve the use of a pair of keys (a public key and a private key) for each participating node. The private key is known only to the node to whom it was issued, while the public key of the node is known to all the participating nodes. These keys are pre-distributed (often before joining the network) to the nodes by a Certification Authority in form of a digital certificate. A digital certificate binds the node identity with the two keys and associates an expiration time with the certificate. The certificate is then signed by the private key of the certification authority to make it tamper proof. To authenticate itself and to access the network services (join the network or start a communication with a member node) a node presents its digital certificate. The existing member nodes can extract the information stored in the certificate by decrypting the certificate using the public key of the certification authority, which is distributed among all participant nodes. The validity of the certificate can then be verified to ensure that the certificate was issued to the node which is presenting the cerificate and that the certificate has not expired yet. If the certificate is valid, the node is allowed to access the services it requested, otherwise, the node is considered a malicious attacker and is denied network access. Note that the certificate of the misbehaving nodes can be revoked. This is achieved through a certificate revocation list that can be maintained at a centralized location where all the revoked certificates can be listed. Several issues specific to ad hoc networks are involved with the above mentioned authentication technique: (i) the decentralized and infrastruc- ture free nature of ad hoc networks make it impractical to have a centralized certification authority; (ii) computational and communicational overhead can be significantly high in case of asymmertic cryptography; and (iii) in the case of misbehaving nodes, certificate revocation can be a callenging task as a centralized certificate revocation list maintainance is impractical.
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  • Spring '12
  • Kushal Kanwar
  • Public key infrastructure, ........., Public-key cryptography, Pretty Good Privacy

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