The compelling advantage of using digital signatures

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The compelling advantage of using digital signatures stems from their capability for non-repudiation. To provide this capability, the user agent of every node will need to append a digital signature to every packet that originates from the node. By doing so, the user agent (or the user) “accepts responsibility” for the packet leaving his/her mobile computer. The signed packet is then encrypted using the one-hop group secret used for enforcing a logical neighborhood. The signatures are verified by the user agents of neighbors, and stripped off before the packets are forwarded onwards. However, every node caches the packets sent by the neighbors (along with the signature) for a small duration (say a few seconds). Whenever an inconsistency is detected, the signed packet could (at a later time) be submitted to the network operators (KDC). For example, a Copyright © 2010. World Scientific Publishing Company. All rights reserved. May not be reproduced in any form without permission from the publisher, except fair uses permitted under U.S. or applicable copyright law. 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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62 M. Ramkumar neighbor common to C and B will be able to submit signed packets from B and C . The network operators (KDC), with access to network agent secrets of all mobiles, can readily determine which of the two nodes acted in a malicious manner. Such nodes may then face the threat of being revoked from the network by the KDC. Note that without non-repudiable signatures, the nodes face very little risk. Some nodes may intentionally introduce malicious modifications to packets relayed so that they can reduce their routing burden. For example, if a malicious node C illegally modifies the RREQ it relays, it can be assured that it will not be a part of the path that is established between the source and the destination. If non-repudiable signatures are mandated, the risk of being revoked from the network is perhaps sufficient motivation for nodes to behave well. While OTS can be used for non-repudiable signatures, digital signa- tures based on asymmetric primitives are clearly preferable in this case as nodes will have to sign every packet. Furthermore, recall that the main dis- advantages of CB based asymmetric schemes are: 1) high computational overhead, which in turn could lead to simple DoS attacks; 2) bandwidth overhead for disseminating certificates. However their main disadvantages are less of an issue in this case as digital signatures appended by nodes need not be carried over , and distribution of certificates to one hop neighbors is not as expensive. Secondly, enforcing private logical neighborhoods elim- inates DoS attacks. As all packet will be encrypted/authenticated using the one-hop group secret, the signature from a node claiming to be A will be verified only after it is ensured that the sender has access to the group secret K A .
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