Word-based compression in full-text retrieval systems

Ankara : Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent University, 1995.Thesis (Master's) -- Bilkent University, 1995.Includes bibliographical references leaves 44-49.Large space requirement of a full-text retrieval system can be reduced significantly by data compression. In this study, the problem of compressing the main text of a full-text retrieval system is addressed and performance of several coding techniques for compressing the text database is compared. Experiments show that statistical techniques, such as arithmetic coding and Huffman coding, give the best compression among the implemented; and using a semi-static word-based model, the space needed to store English text is less than one third of the original requirement.Selçuk, Ali AydınM.S

Secret Sharing Extensions based on the Chinese Remainder Theorem

In this paper, we investigate how to achieve verifiable secret sharing (VSS) schemes by using the Chinese Remainder Theorem (CRT). We first show that two schemes proposed earlier are not secure from an attack where the dealer is able to distribute inconsistent shares to the users. Then we propose a new VSS scheme based on the CRT and prove its security. Using the proposed VSS scheme, we develop joint random secret sharing~(JRSS) and proactive SSS protocols, which, to the best of our knowledge, are the first secure protocols of their kind based on the CRT

Joint Compartmented Threshold Access Structures

In this paper, we introduce the notion of a joint compartmented threshold access structure (JCTAS). We study the necessary conditions for the existence of an ideal and perfect secret sharing scheme and give a characterization of almost all ideal JCTASes. Then we give an ideal and almost surely perfect construction that realizes such access structures. We prove the asymptotic perfectness of this construction by the Schwartz-Zippel Lemma

Server Notaries: A Complementary Approach to the Web PKI Trust Model

SSL/TLS is the de facto protocol for providing secure communication over the Internet. It relies on the Web PKI model for authentication and secure key exchange. Despite its relatively successful past, the number of Web PKI incidents observed have increased recently. These incidents revealed the risks of forged certificates issued by certificate authorities without the consent of the domain owners. Several solutions have been proposed to solve this problem, but no solution has yet received widespread adaption due to complexity and deployability issues. In this paper, we propose a practical mechanism that enables servers to get their certificate views across the Internet, making detection of a certificate substitution attack possible. The origin of the certificate substitution attack can also be located by this mechanism. We have conducted simulation experiments and evaluated our proposal using publicly available, real-world BGP data. We have obtained promising results on the AS-level Internet topology

Sharing DSS by the Chinese Remainder Theorem

In this paper, we propose a new threshold scheme for the Digital Signature Standard (DSS) using Asmuth-Bloom secret sharing based on the Chinese Remainder Theorem (CRT). To achieve the desired result, we first show how to realize certain other threshold primitives using Asmuth-Bloom secret sharing, such as joint random secret sharing, joint exponential random secret sharing, and joint exponential inverse random secret sharing. We prove the security of our scheme against a static adversary. To the best of our knowledge, this is the first provably secure threshold DSS scheme based on the CRT

Güvenli mesajlaşma uygulamalarında kimlik doğrulama ve kullanılabilirlik

26th IEEE Signal Processing and Communications Applications Conference (2018 : Izmir; Turkey)oday, the increasing popularity of instant messaging applications has introduced some security measures. One of these security measures is the authentication activity that users need to make. Authentication in instant messaging applications means verifying that someone is messaging with the right person. In studies conducted to date, users are not able to achieve full success in authentication activities. Therefore, in the four popular instant messaging applications, we conducted the authentication of the authentication key and the change of the authentication key and the user interaction with two different groups of 66 participants. Participants in the first group consisted of 18 participants who worked in the information sector and had no information security knowledge. Participants in the second group consist of 48 university students taking information security course. In the first phase, users were expected to compare the authentication keys. In the second phase, we investigated how users assessed it when the authentication key changed. We observed that, although the participants know that they need to authenticate the other user, they can ignore the authentication process.Aselsan,et al.,Huawei,IEEE Signal Processing Society,IEEE Turkey Section,Neta

Punctured interval broadcast encryption scheme with free riders

In Broadcast Encryption (BE) schemes, the problem is to encrypt a content for a group of dynamically changing privileged (subscriber) subset within a receiver population. A popular approach is to carefully distribute a group of keys to several, carefully designed subsets of the receivers beforehand, and later use a precise subset of keys so that only intended users have those keys, thus decrypt the content. This approach is known as the subset cover framework. In the subset cover framework, one concern is the number of copies that must be encrypted, which affects the bandwidth requirement. This problem can be relaxed by allowing a limited number of free riders so that, by sacrificing some coverage accuracy, the transmission cost is reduced. Several BE schemes are proposed since 90s, and one of the most efficient schemes so far is the punctured interval BE scheme (Cheon et al., 2008). In this paper, we attack the problem of how to assign a given number of free riders effectively in the punctured interval BE scheme. We give the optimal free rider assignment algorithm which runs in poly(n) time, where n is the number of all users in the system, and we provide a heuristic which performs slightly worse than the optimal algorithm in terms of transmission cost reduction but is much faster, i.e., linear in terms of n. We also propose a hybrid approach which employs the core ideas of both optimal and heuristic methods in order to achieve a trade-off between speed and accuracy. (C) 2015 Elsevier Inc. All rights reserved