International Association for Cryptologic Research

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2012-11-26
04:17 [Pub][ePrint]

At NDSS 2012, Yan et al. analyzed the security of several challenge-response type user authentication protocols against passive observers, and proposed a generic counting based statistical attack to recover the secret of some counting based protocols given a number of observed authentication sessions. Roughly speaking, the attack is based on the fact that secret (pass) objects appear in challenges with a different probability from non-secret (decoy) objects when the responses are taken into account. Although they mentioned that a protocol susceptible to this attack should minimize this difference, they did not give details as to how this can be achieved barring a few suggestions.

In this paper, we attempt to fill this gap by generalizing the attack with a much more comprehensive theoretical analysis. Our treatment is more quantitative which enables us to describe a method to theoretically estimate a lower bound on the number of sessions a protocol can be safely used against the attack. Our results include 1) two proposed fixes to make counting protocols practically safe against the attack at the cost of usability, 2) the observation that the attack can be used on non-counting based protocols too as long as challenge generation is contrived, 3) and two main design principles for user authentication protocols which can be considered as extensions of the principles from Yan et al. This detailed theoretical treatment can be used as a guideline during the design of counting based protocols to determine their susceptibility to this attack. The Foxtail protocol, one of the protocols analyzed by Yan et al., is used as a representative to illustrate our theoretical and experimental results.

04:17 [Pub][ePrint]

Image compression and image encryption are pivotal to proper storage and transmission of images over MANET. Simultaneous image compression and encryption aims at achieving enhanced bandwidth utilization and security at the same time. The Number Theory based Image Compression and Quasigroup Encryption (NTICQE) algorithm employs number theoretic paradigm - Chinese Remainder Theorem and Quasigroup Encryption, to solve congruencies and hence realize the twin ideals of compression and encryption simultaneously. Quasigroup encryptor that has very good data-scrambling properties and, therefore, it has potential uses in symmetric cryptography.

04:17 [Pub][ePrint]

In their paper A Quasigroup Based Random Number Generator for Resource Constrained Environments\", the authors Matthew Battey and Abhishek Parakh propose the pseudo random number generator LOQG PRNG 256. We show several highly efficient attacks on LOQG PRNG 256.

04:17 [Pub][ePrint]

Physically Unclonable Functions (PUFs) exploit the physical characteristics of silicon and provide an alternative to storing digital encryption keys in non-volatile memory. A PUF maps a unique set of digital inputs to a corresponding set of digital outputs. In this paper, the use of asynchronous logic and design techniques to implement PUFs is advocated for Asynchronous Physically Unclonable Functions (APUFs). A new method of using asynchronous rings to implement PUFs is described called ASYNCPUF which features inherent field programmability. It is both a novel and holistic PUF design compared to the existing state-of-the-art as it naturally addresses the two challenges facing PUFs to-date that prevent wide-spread adoption: robustness and entropy. Results of electrical simulation in a 90 nano-meter lithography process are presented and discussed.

2012-11-22
01:17 [Pub][JoC]

Abstract  We provide a more general and, in our eyes, simpler variant of Prabhakaran, Rosen and Sahai’s (FOCS ’02, pp. 366–375, 2002) analysis of the concurrent zero-knowledge simulation technique of Kilian and Petrank (STOC ’01, pp. 560–569, 2001).

• Content Type Journal Article
• Pages 1-22
• DOI 10.1007/s00145-012-9137-2
• Authors

• Rafael Pass, Cornell University, Ithaca, NY 14853, USA
• Wei-Lung Dustin Tseng, Google Inc., 747 6th street, Kirkland, WA, USA
• Muthuramakrishnan Venkitasubramaniam, University of Rochester, 621 Computer Sciences Building, Rochester, NY 14627-0226, USA

• Journal Journal of Cryptology
• Online ISSN 1432-1378
• Print ISSN 0933-2790

From: Mon, 19 Nov 2012 15:07:03 GMT

2012-11-21
19:17 [Pub][ePrint]

This article introduces a definition of privacy for Direct Anonymous Attestation schemes. The definition is expressed as an equivalence property suited to automated reasoning using ProVerif and the practicality of the definition is demonstrated by analysing the RSA-based Direct Anonymous Attestation protocol by Brickell, Camenisch & Chen. The analysis discovers a vulnerability in the RSA-based scheme which can be exploited by a passive adversary and, under weaker assumptions, corrupt administrators. A security fix is identified and the revised protocol is shown to satisfy our definition of privacy.

19:17 [Pub][ePrint]

Data access control is an effective way to ensure the data security in the cloud. Due to data outsourcing and untrusted cloud servers, the data access control becomes a challenging issue in cloud storage systems.

Ciphertext-Policy Attribute-based Encryption (CP-ABE), as a promising technique for access control of encrypted data, is very suitable for access control in cloud storage systems due to its high efficiency and expressiveness.

However, the existing CP-ABE schemes cannot be directly applied to data access control for cloud storage systems because of the attribute revocation problem. In this paper, we consider the problem of attribute revocation in multi-authority cloud storage systems where the users\' attributes come from different domains each of which is managed by a different authority.

We propose TAAC (Temporal Attribute-based Access Control), an efficient data access control scheme for multi-authority cloud storage systems, where the authorities are independent from each other and no central authority is needed. TAAC can efficiently achieve temporal access control on attribute-level rather than on user-level. Moreover, different from the existing schemes with attribute revocation functionality, TAAC does not require re-encryption of any ciphertext when the attribute revocation happens, which means great improvement on the efficiency of attribute revocation. The analysis results show that TAAC is highly efficient, scalable, and flexible to applications in practice.

19:17 [Pub][ePrint]

We consider the problem of constructing protocols for secure computation that achieve strong concurrent and composable notions of security in the plain model. Unfortunately UC-secure secure computation protocols are impossible in this setting, but the Angel-Based Composable Security notion offers a promising alternative. Until now, however, under standard (polynomial-time) assumptions, only protocols with polynomially many rounds were known to exist.

In this work, we give the first $\\tilde{O}(\\log n)$-round secure computation protocol in the plain model that achieves angel-based composable security in the concurrent setting, under standard assumptions. We do so by constructing the first $\\tilde{O}(\\log n)$-round CCA-secure commitment protocol. Our CCA-secure commitment protocol is secure based on the minimal assumption that one-way functions exist.

A central tool in obtaining our result is a new \\emph{robust concurrent extraction lemma} that we introduce and prove, based on the minimal assumptions that one-way functions exist. This robust concurrent extraction lemma shows how to build concurrent extraction procedures that work even in the context of an external\'\' protocol that cannot be rewound by the extractor. We believe this lemma can be used to simplify many existing works on concurrent security, and is of independent interest. In fact, our lemma when used in conjunction with the concurrent-simulation schedule of Pass and Venkitasubramaniam (TCC\'08), also yields a constant round construction based additionally on the existence of quasi-polynomial time (\\pqt) secure one-way functions.

19:17 [Pub][ePrint]

The question whether Identity-Based Encryption (IBE) can be based on the Decisional Diffie-Hellman (DDH) assumption is one of the most prominent questions in Cryptography related to DDH. We study limitations on the use of the DDH assumption in cryptographic constructions, and show that it is impossible to construct a secure Identity-Based Encryption system using, in a black box way, only the DDH (or similar) assumption about a group. Our impossibility result is set in the generic groups model, where we describe an attack on any IBE construction that relies on oracle access to the group operation of randomly labelled group elements -- a model that formalizes naturally DDH hardness.

The vast majority of existing separation results typically give separation from general primitives, whereas we separate a primitive from a class of number theoretic hardness assumptions. Accordingly, we face challenges in creating an attack algorithm that will work against constructions which leverage the underlying algebraic structure of the group. In fact, we know that this algebraic structure is powerful enough to provide generic constructions for several powerful primitives including oblivious transfer and chosen ciphertext secure public-key cryptosystems (note that an IBE generalizes such systems). Technically, we explore statistical properties of the group algebra associated with a DDH oracle, which can be of independent interest.

19:17 [Pub][ePrint]

We revisit the concept of public key encryption with delegated keyword search (PKEDS), a concept proposed by Ibraimi et al. A PKEDS scheme allows a receiver to authorize third-party server(s) to search in two ways: either according to a message chosen by the server itself or according to a trapdoor sent by the receiver. We show that the existing formulation has some defects and the proposed scheme is unnecessarily inefficient. Based on our analysis, we present a refined formulation of the primitive with a new security model. We then propose a new PKEDS scheme, which is proven secure and much more efficient than the original scheme by Ibraimi et al.

19:17 [Pub][ePrint]

Predicate encryption (PE) that provides both the access control of ciphertexts and the privacy of ciphertexts is a new paradigm of public-key encryption. An important application of predicate encryption is a searchable encryption system in a cloud storage, where it enables a client to securely outsource its data to an untrusted cloud server and to search over it even without revealing a keyword itself. One practical issue of predicate encryption is to devise an efficient revocation method to revoke a user when the secret key of the user is compromised. Privacy preserving revocable predicate encryption (RPE) can provide not only revocation, but also the privacy of revoked users.

In this paper, we first define two new security models of privacy preserving RPE: the strongly full-hiding security and the weakly full-hiding security. The strongly full-hiding security provides the full privacy of ciphertexts against outside and inside adversaries, but the weakly full-hiding security only provides the full privacy of ciphertexts against an outside adversary who cannot decrypt the challenge ciphertext. Next, we propose two general RPE constructions from any inner product encryption (IPE) schemes, and prove their security. This first RPE scheme provides the strongly full-hiding security, but the size of ciphertexts is proportional to the number of users in the system. The second RPE scheme improves the efficiency of the first RPE scheme such that the size of ciphertexts is sublinear and the decryption algorithm is efficient, but it provides the weakly full-hiding security.