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The access structure of any dictionary is an important one. It provides the user with a means to obtain the required data or to extract valuable information. This dictionary structure mostly overlaps with other structures such as the macro-, micro- and mediostructure, which in turn creates different access routes a dictionary user can follow to try and satisfy his or her lexicographic needs. In printed dictionaries, the access structure can already be found on the cover, while in electronic or online dictionaries this structure is usually visible on the home or landing page (Du Plessis 2015: 51-52). Gouws and Prinsloo (2005: 64) differentiate between two types of access structures: the outer access structure, which relates to the access or search routes that lead a user to the lemma sign, and the inner access structure, which, among other things, involves the search routes and zones within a dictionary article. The traditional functions and uses of dictionary structures are adapted for the online and mobile medium in order to better satisfy user needs. The disadvantage of this, however, is that it is becoming increasingly difficult to distinguish between different dictionary structures (Müller-Spitzer 2013: 368-369). Fortunately, e-dictionaries have the freedom to provide new and innovative ways for users to access lexicographic material. The goal of this article is to highlight and evaluate some of these innovative access routes, particularly in mobile dictionaries. This is done to determine which access routes deserve further investigation or should be considered as a standard practice in mobile and other e-dictionaries.

The methods for sharing a secret image using Boolean operations are good candidates for Visual Secret Sharing (VSS) as limiting pixel expansion and the reconstruction process computational complexity in VSS schemes. The existing Boolean operations-based secret image sharing (SIS) schemes can only handle the sharing of a secret for ( k ,  n )-threshold and general access structure. This paper extends the Boolean operations-based SIS scheme for Compartmented access structure. Two construction techniques are proposed to realize the sharing of a secret image into Compartmented access structure. The proposed scheme benefits by having wide applicability with better visual quality of the reconstructed secret and without involving complex computation in the reconstruction process. Formal proofs and experimental results are given to validate the correctness, security and performance of the proposed scheme.

The modern medical system is convergence of cutting-edge technologies and advancements in the healthcare environment. In the modern medical system, the storage of electronic health records is generally leased out to third-party cloud service providers (CSPs). But, CSPs cannot be entirely relied upon due to the potential security and privacy issues. This article presents Multi-Authority and Hierarchical Attribute-Based Encryption Scheme (MH-ABE) scheme to promote secure information sharing and protect patient’s privacy. The utilization of CP-ABE in conjunction with multiple Attribute Authorities within the proposed MH-ABE scheme presents a scalable and fine-grained approach to data access control. The proposed MH-ABE scheme incorporates the utilization of a Hierarchical Access Tree to effectively encrypt numerous files concurrently, hence reducing the computational and storage cost. The proposed scheme has also been evaluated using a comparative analysis with existing schemes, emphasizing the assessment of computational and storage costs. The findings of this analysis demonstrate improved performance and efficiency of the proposed ciphertext policy based encryption scheme. The proposed MH-ABE scheme incorporates features such as policy hiding and revocation, and it exhibits resilience against attacks, including collusion resistance, Indistinguishability under chosen-plaintext attack and forward secrecy.

Visual cryptography is an interesting secret sharing scheme, in which participants can observe the secret image by stacking their shares. However, the size expansion and distorted visual effect are two disadvantages of visual cryptography. In this paper, we focus on how to realize the perfect recovery by XOR-ing shares directly. First, we propose the definition of ideal access structure, which is the key point of perfect recovery of XOR-based visual cryptography scheme. The characteristics of ideal access structure are analyzed, and the construction algorithm of shares under ideal access structure is designed. Based on the ideal access structure, a new algorithm is proposed for dividing the general access structure into several ideal access structures, and the secret sharing and recovering algorithms for general access structure are presented. Furthermore, our method can also be utilized in color visual cryptography and multi-secret visual cryptography. The security and perfect recovery of our method have been proved theoretically. Compared with the previous schemes, the proposed scheme realizes the perfect recovery of secret image by XOR-ing shares directly, and the sizes of shares can be decreased efficiently compared with the previous schemes.

Multipartite secret sharing schemes have been an important object of study in the area of secret sharing schemes. Two interesting families of multipartite access structures are hierarchical access structures and compartmented access structures. This work deals with efficient and explicit constructions of ideal compartmented secret sharing schemes, while most of the known constructions are either inefficient or randomized. We construct ideal linear secret sharing schemes for three types of compartmented access structures, such as compartmented access structures with upper bounds, compartmented access structures with lower bounds, and compartmented access structures with upper and lower bounds. There exist some methods to construct ideal linear schemes realizing these compartmented access structures in the literature, but those methods are inefficient in general because non-singularity of many matrices has to be determined to check the correctness of the scheme. Our constructions do not need to do these computations. Our methods to construct ideal linear schemes realizing these access structures combine polymatroid-based techniques with Gabidulin codes. Gabidulin codes play a fundamental role in the constructions, and their properties imply that our methods are efficient.

A secret sharing scheme (SSS) was introduced by Shamir in 1979 using polynomial interpolation. Later it turned out that it is equivalent to an SSS based on a Reed–Solomon code. SSSs based on linear codes have been studied by many researchers. However there is little research on SSSs based on additive codes. In this paper, we study SSSs based on additive codes over GF (4) and show that they require at least two steps of calculations to reveal the secret. We also define minimal access structures of SSSs from additive codes over GF (4) and describe SSSs using some interesting additive codes over GF (4) which contain generalized 2-designs.

Die toegangstruktuur van enige woordeboek is 'n belangrike struktuur omdat dit vir gebruikers 'n manier gee om die verlangde data te verkry of inligting te onttrek. Hierdie struktuur oorvleuel dikwels met alle ander woordeboekstrukture, hetsy die makro-, mikro- of kruisverwysingstruktuur, en sodoende vorm al hierdie strukture in werklikheid die roetes wat gebruikers volg om sy of haar leksikografiese behoeftes te probeer bevredig. In gedrukte woordeboeke word die toegangstruktuur reeds op die voorblad aangetref, terwyl dit in elektroniese of aanlyn woordeboeke gewoonlik al op die tuis- of landingsblad sigbaar is (Du Plessis 2015: 51-52). Gouws en Prinsloo (2005: 64) verwys na twee verskillende tipes toegangstrukture, naamlik die eksterne toegangstruktuur, wat verband hou met die soekroetes wat die gebruiker na die lemma neem, en die interne toegangstruktuur, wat o.a. die soekroetes en -sones binne die artikel self behels. Met aanlyn en selfoonwoordeboeke word die tradisionele funksies en gebruike van woordeboekstrukture aangepas vir die medium en om die gebruiker se behoeftes vinniger en makliker te bevredig. Dit het egter die gevolg dat dit soms moeilik is om tussen die verskillende woordeboekstrukture te onderskei (Müller-Spitzer 2013: 368-369). Die gelukkige toeval daarvan is dat e-woordeboeke meer vryheid het om op nuwe en innoverende maniere gebruikers na leksikografiese materiaal te lei. Hierdie artikel het ten doel om van hierdie innoverende toegangsroetes in veral selfoonwoordeboeke uit te lig en te evalueer. Dit word gedoen ten einde te bepaal watter toegangsroetes verdere aandag verdien of wat as standaardpraktyk in selfoon- en ander e-woordeboeke oorweeg moet word.

Weighted threshold secret sharing was introduced by Shamir in his seminal work on secret sharing. In such settings, there is a set of users where each user is assigned a positive weight. A dealer wishes to distribute a secret among those users so that a subset of users may reconstruct the secret if and only if the sum of weights of its users exceeds a certain threshold. On one hand, there are nontrivial weighted threshold access structures that have an ideal scheme--a scheme in which the size of the domain of shares of each user is the same as the size of the domain of possible secrets (this is the smallest possible size for the domain of shares). On the other hand, other weighted threshold access structures are not ideal. In this work we characterize all weighted threshold access structures that are ideal. We show that a weighted threshold access structure is ideal if and only if it is a hierarchical threshold access structure (as introduced by Simmons), or a tripartite access structure (these structures generalize the concept of bipartite access structures due to Padró and Sáez), or a composition of two ideal weighted threshold access structures that are defined on smaller sets of users. We further show that in all those cases the weighted threshold access structure may be realized by a linear ideal secret sharing scheme. The proof of our characterization relies heavily on the strong connection between ideal secret sharing schemes and matroids, as proved by Brickell and Davenport.

The close interaction between linguistics and lexicography over the last few decades has had many good effects, not least of which has been the development of a theoretical framework or meta lexicography. However, this close link has had an unfortunate result: the marginalisation in the theoretical debate of nonlinguistic dictionaries and especially of the encyclopaedia. In this article, semantic, lexicographical and pragmatic motivations will be given for a renewed interest in encyclopaedias. The revolution caused by CD-ROM encyclopaedias and the benefits they hold for a large spectrum of users, will be the most important pragmatic motivations addressed. Microsoft Encarta 99 Encyclopedia will act as a guide for the exploration of the impact this revolution has had on the ideas of user-friendliness and dictionary accessibility. Finally, a future is envisioned in which the Internet will be the logical culmination of the ultimate potential of computers as accessible, user-friendly reference tools.

Attribute-based encryption with keyword search（ABKS） enables data owners to grant their search capabilities to other users by enforcing an access control policy over the outsourced encrypted data. However,existing ABKS schemes cannot guarantee the privacy of the access structures, which may contain some sensitive private information. Furthermore, resulting from the exposure of the access structures, ABKS schemes are susceptible to an off-line keyword guessing attack if the keyword space has a polynomial size. To solve these problems, we propose a novel primitive named hidden policy ciphertext-policy attribute-based encryption with keyword search（HP-CPABKS）. With our primitive, the data user is unable to search on encrypted data and learn any information about the access structure if his/her attribute credentials cannot satisfy the access control policy specified by the data owner. We present a rigorous selective security analysis of the proposed HP-CPABKS scheme, which simultaneously keeps the indistinguishability of the keywords and the access structures. Finally,the performance evaluation verifies that our proposed scheme is efficient and practical.