In chained ots 6 schemes commitments for several otss

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In chained OTS 6 schemes commitments for several OTSs are chained together to form a special hash chain. 5 While such schemes are for in- stantaneous verification, they are delay sensitive. Some s -times signature schemes have also been proposed. Such a scheme with parameters t, k where ( t k ) > 2 m can be used for signing m -bit messages with O ( k ) signature size and O ( t ) public key size. 7 TESLA vs OTS: Consider a scenario where a node C receives a TESLA authenticated message originating from A at some time t and that the key (from A ’s TESLA chain) used for authenticating the message is ex- pected to be A ’s secret till time t 1 t . At some time t 2 t 1 when A reveals the secret, C can now verify that the message did indeed originate from A . However it is not possible for C to prove to another node D (which did not receive A ’s message before time t 1 ) that the message did indeed originate from A . Thus one practical ramification of the delay sensitivity of TESLA is that TESLA cannot be used for non-repudiation . On the other hand, digital signatures (based on public key schemes) and OTS schemes are i) delay insensitive; and ii) facilitate instantaneous verification. Anyone can verify that the message was sent by A , at any time. Thus such schemes can be used for non-repudiation. However, while a public-private key pair of conventional public key schemes can be used for signing unlimited number of messages, an OTS key pair can be used for signing only one message. Multiple commitments can be efficiently disseminated using Merkle hash trees. 3.1.3. Merkle Tree Both TESLA and OTS require that certified commitments of nodes are “made available” to all potential verifiers. In general, each node may be associated with multiple commitments as i) one commitment is needed for every signed message in OTS schemes; and ii) a TESLA hash chain (corre- sponding to a commitment) can be used only between a specific interval of time. A Merkle hash tree 8 is a useful construct for certifying a large number of commitments using a single commitment (which is provided to all potential verifiers). To commit 2 L values using a Merkle tree, a binary tree of depth L is constructed. Figure 1 depicts a Merkle tree for L = 3. The 2 L leaves of the tree say, C L 0 · · · C L 2 L 1 are first blinded by hashing it once, leaving 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 39 2 L blinded leaf values V L 0 · · · V L 2 L 1 where V L i = h ( C L i ). The 2 L values V L 0 · · · V L 2 L 1 are paired, and each pair are hashed together to create a new value as a commitment for both values (for example, in the figure V 2 1 = h ( V 3 2 , V 3 3 )). Thus at depth L
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  • Spring '12
  • Kushal Kanwar
  • Public key infrastructure, ........., Public-key cryptography, Pretty Good Privacy

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