International Association for Cryptologic Research

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2013-08-14
15:17 [Pub][ePrint]

Coppersmith described at Eurocrypt 96 a polynomial-time algorithm for finding small roots of univariate modular equations, based on lattice reduction. In this paper we describe the first improvement of the asymptotic complexity of Coppersmith\'s algorithm. Our method consists in taking advantage of Coppersmith\'s matrix structure, in order to apply LLL algorithm on a matrix whose elements are smaller than those of Coppersmith\'s original matrix. Using the $L^2$ algorithm, the asymptotic complexity of our method is $O(\\log^{6+\\epsilon} N)$ for any $\\epsilon > 0$, instead of $O(\\log^{8+\\epsilon} N)$ previously. Furthermore, we devise a method that allows to speed up the exhaustive search which is usually performed to reach Coppersmith\'s theoretical bound. Our approach takes advantage of the LLL performed to test one guess, to reduce complexity of the LLL performed for the next guess. Experimental results confirm that it leads to a considerable performance improvement.

15:17 [Pub][ePrint]

In past years a body of data integrity checking techniques have been proposed for securing cloud data services. Most of these work assume that only the data owner can modify cloud-stored data. Recently a few attempts started considering more realistic scenarios by allowing multiple cloud users to modify data with integrity assurance. However, these attempts are still far from practical due to the tremendous computational cost on cloud users. Moreover, collusion between misbehaving cloud servers and revoked users is not considered. This paper proposes a novel data integrity checking scheme characterized by multi-user modification, collusion resistance and a constant computational cost of integrity checking for cloud users, thanks to our novel design of polynomial-based authentication tags and proxy tag update techniques. Our scheme also supports public checking and efficient user revocation and is provably secure. Numerical analysis and extensive experimental results show the efficiency and scalability of our proposed scheme.

15:17 [Pub][ePrint]

Searching an object from a large set is a tedious task. Radio Frequency IDentification (RFID) technology helps us to search the desired object efficiently. In this technology, a small chip called RFID tag, that contains the identification information about an object is attached to the same object. In general, a set of objects are attached with RFID tags. To find out a particular object preserving the possible security requirements, the RFID reader requests the tag in desired object to respond with its encrypted identification information. Since there is a response only from the tag in desired object the adversary gets the knowledge of existence of the desired object. Fake response from tag in undesired objects may fool the adversary. However, computation for fake responses is

an overhead. In this paper, we propose a search technique which has a negligible amount of computation for fake responses. Multiple tags in the same object increases the detection probability and also the probability of success in search process. Our aim is to search a particular object efficiently preserving the possible security requirements amid various resource limitations in low-cost RFID tag.

15:17 [Pub][ePrint]

may access classified information about an object tagged with RFID tag. Therefore, authentication is a necessary requirement. Use of multiple tags in an object increases the detection probability and simultaneously ensures availability of multiple resources in the form of memory and computability. Authentication process in multi-tag arrangement may increase the traffic between reader and object and/or decrease the detection probability. Therefore the challenge is to keep intact the detection probability without increasing the traffic. Existence of multiple number of tags helps to distribute the authentication responsibility for an object among multiple number of tags. In this paper, we assume that an object is attached with multiple number of active tags and in each session a randomly selected tag is responsible for authentication process. The detection probability is intact since an active tag within the range of reader can be an inter-mediator.

15:17 [Pub][ePrint]

The GHS attack is known as a method to map the discrete logarithm problem(DLP) in the Jacobian of a curve C_{0} defined over the d degree extension k_{d} of a finite field k to the DLP in the Jacobian of a new curve C over k which is a covering curve of C_{0}. Such curves C_{0}/k_{d} can be attacked by the GHS attack and index calculus algorithms. In this paper, we will classify all elliptic curves and hyperelliptic curves C_{0}/k_{d} of genus 2, 3 which possess (2,...,2) covering C/k of \\Bbb{P}^1 under the isogeny condition (i.e. g(C)=d \\cdot g(C_{0})) in odd characteristic case. Our main approach is analysis of ramification points and representation of the extension of Gal(k_{d}/k) acting on the covering group cov(C/\\Bbb{P}^1). Consequently, all explicit defining equations of such curves C_0/k_d and existential conditions of a model of C over k are provided.

2013-08-12
11:28 [Event][New]

Submission: 31 August 2013
From December 11 to December 13
Location: Dalian, China

2013-08-10
18:27 [Event][New]

Submission: 30 September 2013
From September 30 to September 30
Location: Lausanne, Switzerland

2013-08-09
20:42 [Event][New]

Submission: 20 August 2013
From November 13 to November 15
Location: Dallas, USA

06:58 [Event][New]

Submission: 22 August 2013