Abstracts:

Traditional group signature schemes reflect only one side of the spectrum of public cryptography, i.e., signing, where the group public key is used for a sole purpose: verification of group signatures. This paper describes a new group cryptographic system that presents a promise for both signing and encryption. That is, besides verifications, a sole group public key can be also used for encryption and the associated decryption can be implemented by any member in the designated group. The proposed system meets all key features for an ideal group cryptography. (pp. 249-254)

Keywords: key cryptography, group signature, distributed encryption

At PKC 2000, Inoue and Sakurai proposed some methods to design hash functions from block ciphers and codes (block codes and convolutional codes). They claimed that their hash functions are secure: 2^((d-1)m/2) encryptions are necessary to find a collision, where d and m are the minimal distance of the code and the block size of block cipher, respectively. However, we show in this paper that a collision could be found with about alpha*2^m encryptions, where alpha is a small number. (pp. 255-258)

Keywords: cryptanalysis, hash function, block cipher, codes

We investigate the security of the AES S-box in the view of Boolean function with the technique of Walsh spectrum. The cryptographic characteristics of AES such as linearity, nonlinearity, strict avalanche, propagation and correlation immunity are revealed. (pp. 259-262)

Keywords: AES, S-box, Boolean function, Walsh spectrum

Multicast Re-keying means the establishment of a new session key for the new subgroup in the multicast system. Practical construction methods for multicast re-keying scheme using Reed-Solomon codes and Algebraic-Geometric codes are presented in this paper with examples to show the detailed constructions. The constructions require no computational assumptions. The storage complexity for group members(Group Controller and other users) and the transmission complexity for the schemes have been reduced to O(log(n)) at the same time. (pp. 263-270)

Keywords: Multicast, Re-keying, Reed-Solomon code, Hash function, KDP

Cheating in multisecret sharing is considered. Multisecret sharing is defined by a mapping F: GF(p^t)^n -> GF(p^t)^m that provides a generic model. In this model, we propose nonlinear multisecret sharing that is immune against cheaters. Two cheating strategies are considered. In the first one, all cheaters always submit their invalid shares and they collectively know their own valid shares. In the second one, some cheaters may submit their valid shares while again sharing their knowledge about their valid shares. The combiner (or recovery algorithm) interacts with shareholders by collecting shares from them and distributing the recovered secrets back to active participants. Two different scenarios are considered when the combiner recreates all secrets (this is simultaneous recovery) or gradually (so called sequential recovery). Probabilities of successful cheating are derived and constructions for cheating immune multisecret sharing are given. (pp. 271-278)

Keywords: Secret Sharing, Multisecret Secret Sharing, Cheating Immune Secret Sharing

The theory Information Hiding and in particular Watermarking (WM) still remains uncompleted. There have been some advances in asymptotic theory concerning capacity of WM as well as in some practical proposals, mainly where WM is applied without any theory. Most of times, references are made to public watermarking, in which the watermark detector does not require any secret key at all. In this paper, our contribution is a WM that we name semipublic watermarking. This is a scenario in which any ordinary user is enabled to detect WM without any secret key, if the message is not subject of attack trying to
remove its WM. Moreover, at any time, the owner of WM is able to detect WM even after such an attack. We propose two methods of semipublic WM and we calculate the probabilities Pm, of missing WM (when WM is present, indeed), and Pfa of WM false alarm (when WM is absent but its presence is supposed). The first method guarantees that both Pm and Pfa converge to zero as the number N of WM elements increases, only if the distortion constraints are very strong. In second method also Pm, Pfa converge to zero as N increases, for any distortion constraints, but it is required the so called property of quadratic compensation: In order to compensate an m times increase of the distortion constraint ``signal-to-noise ratio'', the number at WM elements should increase m^2 times. Although we consider just additive noise attacks, our results are useful since they provide lower bounds for WM reliability for any optimal attack with given distortion constraints. (pp. 279-286)

Keywords: information security, copyright protection, information hiding, watermarking

An anonymous fingerprinting scheme was presented by Domingo, which can identify the redistributors without the help of registration authority. However, this scheme on average requires N/2 exponential operations when the merchant identifies the redistributors, where N is the number of public keys in the directory. Chanjoo Chung proposed a more efficient scheme than Domingo’s, but there is a fatal weakness in the proposed registration protocol of his scheme. This weakness causes that any impersonator can personate an honest buyer with the probability of 1/2. In this paper, we give an efficient scheme that requires only one exponential operation, which improves the whole scheme’s efficiency. Security analysis is also given at last. (pp. 287-290)

Keywords: Anonymous Fingerprinting, Digital Fingerprinting, Digital Watermarking, TTP, STPC

Changjie Wang and Yumin Wang
National Key Lab. On ISN, Xidian University, Xi’an 710071, P.R.China
E-mail: cjwang@ee.cityu.edu.hk, ymwang@xidian.edu.cn
AND
Fangguo Zhang
CAIS Lab. ICU (Information and communications Univ.), Korea
E-mail: zhfg@icu.ac.kr

A major problem of mobile agents is their apparent inability to authenticate transactions in hostile environments. In this paper, we propose a new secure anonymous mobile agent scheme for the prevention of agent tempering without compromising the mobility or autonomy of the agent. In our scheme, a mobile agent can produce valid signature on Website’s bid (means that transact a contact with the Web site) on behalf of its customer, without leaking the customer’s really private key. In addition, the anonymity of the customer is also achieved when its agent transacting with the Websites. Furthermore, the customer who issued a malicious agent or deny the transaction can be identified and revealed by Agent Management Center (AMC). Therefore, our scheme is practical in the future electronic commerce over Internet. (pp. 291-298)

Keywords: Mobile Agent, Digital Signature, Anonymity and Electronic Commerce

Toma˛ Erjavec
Department of Intelligent Systems, Jo˛ef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia
E-mail: tomaz.erjavec@ijs.si
Website: http://nl.ijs.si/et/

With increasing amounts of text being available in electronic form, it is becoming relatively easy to obtain digital texts together with their translations. The paper presents the processing steps necessary to compile such texts into parallel corpora, an extremely useful language resource. Parallel corpora can be used as
a translation aid for second-language learners, for translators and lexicographers, or as a data-source for various language technology tools. We present our work in this direction, which is characterised by the use of open standards for text annotation, the use of publicly available third-party tools and wide availability of the produced resources. Explained is the corpus annotation chain involving normalisation, tokenisation, segmentation, alignment, word-class syntactic tagging, and lemmatisation. Two exploitation results over our annotated corpora are also presented, namely a Web concordancer and the extraction of bi-lingual lexica (pp. 299-308)

Keywords: natural language processing, corpus annotation, multilinguality, lexicon extraction

Daniele Frigioni, Laura Tarantino and Tania Di Mascio
Dipartimento di Ingegneria Elettrica, Universita degli Studi dell'Aquila, I-67040 Monteluco di Roio, L'Aquila - Italy
E-mail: frigioni@ing.univaq.it, laura@ing.univaq.it, tania@ing.univaq.it

Partitions have been identified as a key concept for perception and understanding of space, and have been regarded as a primary tool for spatial analysis tasks in geographic applications. We discuss here some results regarding the exploration of geographic maps structured as nested partitions. In particular, we present a zooming model based on a Level-Of-Detail (LOD) approach, aimed at visualizing sequences of gradually simplified representations of a given area hierarchically structured in a poset. We first describe a set of basic zooming primitives defined as transitions betweens maps at different LOD, and study properties of the corresponding map space. We then introduce the notion of multiple zooming, define two new multiple zooming primitives on top of the basic ones, extend the map space, and prove some theoretical results on the new primitives. (pp. 309-320)

Keywords: Geographic Map, Poset, Human-Computer Interaction

David Taniar
School of Business Systems, Monash University, PO Box 63B, Clayton, Vic 3800, Australia
E-mail: David.Taniar@infotech.monash.edu.au
AND
Y. Jiang, K.H. Liu and C.H.C. Leung
School of Communications and Informatics, Victoria University, P.O Box 14428 MCMC, Melbourne 8001, Australia

Queries containing aggregate functions often combine multiple tables through join operations. We call these queries "Aggregate-Join" queries. In parallel processing of such queries, it must be decided which attribute to be used as a partitioning attribute, particularly join attribute or group-by attribute. Based on the partitioning attribute, we discuss three parallel aggregate-join query processing methods, namely Join Partition Method (JPM), Aggregate Partition Method (APM), and Hybrid Partition Method (HPM). The JPM and APM models use the join attribute, and the group-by attribute, respectively, as the partitioning attribute. The HPM model combines the other two methods using a logically hybrid architecture. Our performance results show that the HPM model outperforms the others. In the performance evaluation, we also incorporate the problem of skew, which may occur at the data level, as well as at the processing level. (pp. 321-332)

Keywords: Aggregate-Join Queries, Parallel Query Processing, Parallel Databases, and Parallel Aggregate Query Processing

Adel Taweel and Pearl Brereton
Department of Computer Science, Keele University, Keele, Staffordshire ST5 5BG, UK
E-mail: a.taweel or o.p.brereton@cs.keele.ac.uk
Website: www.keele.ac.uk/depts/cs

Market forces and an increasingly reliable world-wide communications network have made geographically distributed software engineering a reality. Global software development enables businesses to respond more easily and more quickly to global market opportunities and to improve product and service quality. One of the many potential benefits of global development is a reduction in development time through the adoption of an ‘around the clock’ working practice.
This paper introduces a sequential collaborative software engineering process involving shift working across time zones and describes an exploratory empirical study of this working pattern involving the implementation of a small-scale software system. The paper reports on the organisation of the study and on the results obtained through questionnaires, observations and measurements. (pp. 333-344)

Keywords: global software development, collaborative working, distributed software engineering, virtual teams