Dedicated hash functions are cryptographically secure compression functions which are designed specifically for hashing. They intend to form a practical alternative for hash functions based on another cryptographic primitive like a block cipher or modular squaring. About a dozen of dedicated hash functions have been proposed in the literature. This paper discusses the design principles on which these hash functions are based.

We present a binary tree based parallel algorithm for extending the domain of a UOWHF. The key length expansion is 2m bits for t = 2; m(t+1) bits for 3 t 6 and m(t+blog 2 (t 1)c) bits for t 7, where m is the length of the message digest and t 2 is the height of the binary tree. The previously best known binary tree algorithm required a key length expansion of m 2(t 1) bits. We also obtain the lower bound that any binary tree based algorithm must make a key length expansion of 2m bits if t = 2 and a key length expansion of m (t + 1) bits for t 3. Hence for 2 t 6 our algorithm makes optimal key length expansion and for practical sized processor trees the key length expansion is close to the lower bound.

We study the problem of securely extending the domain of a collision resistant compression function. Our rst contribution is to show that given an arbitrary directed acyclic graph and a collision resistant compression function, it is possible to construct a collision resistant hash function. Next we introduce a new technique for constructing a hash function which can handle arbitrary length strings. The amount of padding and the number of invocations of the compression function required by our algorithm is asymptotically smaller compared to the Merkle-Damgard algorithm. Our third contribution is to provide some concrete examples and hence derive the foundation for the design of a secure parallel hash algorithm.

Efficient Resource discovery mechanism is one of the fundamental requirement for Grid computing systems, as it aids in resource management and scheduling of applications. Resource discovery activity involve searching for the appropriate resource types that match the user’s application requirements. Various kinds of solutions to grid resource discovery have been suggested, including the centralised and hierarchical information server approach. However, both of these approaches have serious limitations in regards to scalability, fault-tolerance and network congestion. To overcome these limitations, indexing resource information using a decentralised (such as Peer-to-Peer (P2P)) network model has been actively proposed in the past few years. This article investigates various decentralised resource discovery techniques primarily driven by P2P network model. To summarise, this article presents a: (i) summary of current state of art in grid resource discovery; (ii) resource taxonomy with focus on computational grid paradigm; (iii) P2P taxonomy with focus on extending the current structured systems (such as Distributed Hash Tables) for indexing d-dimensional grid resource queries; (iv) detailed survey of existing works that can support d-dimensional grid resource queries; and (v) classification of the surveyed approaches based on the proposed P2P taxonomy. We believe that this taxonomy and its mapping to relevant systems would be useful for academic and industry based researchers who are engaged in the design of scalable Grid and P2P systems. 1

Efficient Resource discovery mechanism is one of the fundamental requirement for Grid computing systems, as it aids in resource management and scheduling of applications. Resource discovery activity involve searching for the appropriate resource types that match the user’s application requirements. Various kinds of solutions to grid resource discovery have been suggested, including the centralised and hierarchical information server approach. However, both of these approaches have serious limitations in regards to scalability, fault-tolerance and network congestion. To overcome these limitations, indexing resource information using a decentralised (such as Peer-to-Peer (P2P)) network model has been actively proposed in the past few years. This article investigates various decentralised resource discovery techniques primarily driven by P2P network model. To summarise, this article presents a: (i) summary of current state of art in grid resource discovery; (ii) resource taxonomy with focus on computational grid paradigm; (iii) P2P taxonomy with focus on extending the current structured systems (such as Distributed Hash Tables) for indexing d-dimensional grid resource queries 1; (iv) detailed survey of existing works that can support d-dimensional grid resource queries; and (v) classification of the surveyed approaches based on the proposed P2P taxonomy. We believe that this taxonomy and its mapping to relevant systems would be useful for academic and industry based researchers who are engaged in the design of scalable Grid and P2P systems. 1

We propose a new infinite family of cryptographic hash functions, Edon–R, based on a recently defined candidate one-way function. Edon–R is a class of hash functions with variable output lengths. It is defined using quasigroups and quasigroup string transformations.

Abstract. We revisit the enhanced target collision resistance (eTCR) property as a newly emerged notion of security for dedicated-key hash functions, which has been put forth by Halevi and Krawczyk at CRYPTO’06, in conjunction with the Randomized Hashing mode to achieve this property. Our contribution is twofold. Firstly, we provide a full picture of the relationships between eTCR and each of the seven security properties for a dedicatedkey hash function, considered by Rogaway and Shrimpton at FSE’04; namely, collision resistance (CR), the three variants of second-preimage resistance (Sec, aSec, eSec) and the three variants of preimage resistance (Pre, aPre, ePre). The results show that, for an arbitrary dedicated-key hash function, eTCR is not implied by any of these seven properties, and it can only imply three of the properties; namely, eSec (TCR), Sec, Pre. In the second part of the paper, we analyze the eTCR preservation capabilities of several domain extension transforms (a.k.a. modes of operation) for hash functions, including (Plain, Strengthened, and Prefix-free) Merkle-Damg˚ard, Randomized Hashing, Shoup, Enveloped Shoup, XOR Linear Hash (XLH), and Linear Hash (LH). From this analysis it turns out that, with the exception of a nested variant of LH, none of the investigated transforms can preserve the eTCR property.

Commitment schemes are building blocks for guaranteeing fairness in higher-level cryptographic protocols such as mental poker protocols and others. A party Alice commits to a value v (a bit or a bitstring) without revealing it. Alice should not be able to cheat by opening the commitment as v nor to deny having committed at all. Most commitment schemes in the literature rely on hash functions, which should be strongly collision-free for the scheme to be secure. Yet collision-freeness can only be empirically checked and cannot be met with total certainty. We present a commitment scheme which avoids hash functions by using a public-key cryptosystem instead.

this paper, we consider

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