Thus the private keys r a of an entity a are assigned

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Thus the private key(s) R A of an entity A are assigned by the KDC to A . With IB schemes two nodes A and B can independently compute a shared secret K AB without exchanging certificates for this purpose. IB public key schemes for encryption and signatures, 1 most of which take advantage of pairings in special elliptic curve groups, have attracted substantial attention recently. 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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Key Distribution 35 3. Schemes Based on Symmetric Cryptography The CB and IB schemes based on asymmetric primitives provide both one- to-one (establishment of pairwise secrets) and one-to-many SAs (in the form of digital signatures). On the other hand, schemes based only on symmetric primitives are less versatile. Some schemes can be used only for establishment of pairwise secrets. Some schemes can be used only for source authentication (and thus cannot be used to establish a private channel). More specifically, ID based key predistribution schemes (KPS) permit two nodes A and B to independently compute a common secret K AB with- out any exchanges, and without the need for a mediator (after keys have been predistributed to entities by a KDC). In a scenario where A intends to authenticate its message to multiple verifiers, say B , C , and D , node A can append independent HMACs based on individually shared secrets K AB , K AC and K AD respectively. However, in scenarios where the num- ber of verifiers are large, such an approach is inefficient. Furthermore, in scenarios where the A does not have a priori knowledge of the identities of potential verifiers, it is simply not possible for A to append individual HMACs. Several certificate based source authentication schemes employing only symmetric primitives (all of which utilize one-way hash functions) exist for one-to-many SAs, where the authentication appended by a message source can be verified by any verifier. 3.1. CB Schemes for One-to-many SAs Source authentication schemes employing only symmetric primitives in- clude several CB schemes like one-time signature (OTS) schemes, s -time signature schemes, chained OTS schemes, TESLA, and per-use (PU) hash chains. In this chapter we limit ourselves to OTS, TESLA and PU hash chains. 3.1.1. TESLA In the TESLA 2 broadcast authentication scheme, a node A chooses a ran- dom secret K 0 A and creates a one-way hash chain { K 0 A , K 1 A , . . . , K L A } , where K i A = h ( K i 1 A ). The hash chain is associated with two parameters: i) T 1 - an absolute value of time; and ii) a time interval ∆. The value K L 1 A is associated with time T 1 , K L 2 A with time T 2 = T 1 + ∆, and more generally, K L i A , with time T i = T 1 + ( i 1)∆. The nature of the association is that Copyright © 2010. World Scientific Publishing Company. All rights reserved. May not be reproduced in any form without permission from the publisher, except fair uses
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