중복제거 테이블을 이용한 특이점 절충기법과 그의 병렬처리에 대한 분석

학위논문 (박사)-- 서울대학교 대학원 : 수리과학부, 2016. 2. 홍진.In a recent paper, the performances of three major time memory tradeoff algorithms, namely, the classical Hellman tradeoff and the non-perfect table versions of the distinguished point(DP) and the rainbow table tradeoff methods, were analyzed and compared against each other. The analysis was accurate in the sense that the extra costs of resolving false alarms were not ignored, and the performance comparison was fair in the sense that both the online complexity and the pre-computation cost were taken into account and the techniques for optimizing storage size were taken into account. Based on this paper, another recent paper analyzed a DP variant, which treats the non-perfect DP tables in parallel, and compared its performance with those of the previous three tradeoff algorithms. In this thesis, we analyze the performances of three more tradeoff algorithms and compare them with the aforementioned four algorithms. The algorithms newly considered here will be the perfect table versions of the DP, rainbow table, and parallel DP tradeoff methods. The performance of an algorithm cannot be represented by a single numeric value and algorithm preferences will depend on the available resources and various situations faced by the tradeoff algorithm implementer. Hence, we will present the performances of the tradeoff algorithms as curves providing the full range of options made available by the algorithms, so as to allow for the implementers to make their choices. However, our comparisons show that, under typical situations, the perfect table parallel DP tradeoff algorithm is more likely to be preferable over the other DP algorithm variants and that the perfect rainbow table method is superior to the other tradeoff algorithms. On the other hand, yet another recent paper notes that the perfect rainbow table method is widely implemented in practice to process its pre-computation tables in a serial manner, rather than in parallel, as was originally proposed by the algorithm designers. This is because, even though the parallel treatment of the pre-computation tables would be more efficient in theory, the size of tables are too large to be fully loaded into fast main memory in real-world applications such as password recovery and this affects the real-world performances of the algorithms negatively. Following the approach of the paper, we give the optimal physical wall-clock online execution times for the practically used serial perfect rainbow and the perfect table versions of the DP and rainbow tradeoffs that treat their pre-computation tables in parallel. This is done with various realistic password spaces and at various high success rate requirements, under a specific limitation on the size of available storage. Unlike any theoretical approach to the tradeoff algorithms, the physical online execution time includes the time taken for loading the pre-computation tables from disk to fast memory and the time taken by table lookups. We find that, in contrast with the software developers' intuition, the serial perfect rainbow tradeoff algorithm is inferior to the two algorithms that treat their tables in parallel, when their optimal physical online times are compared under reasonable assumptions and settings. Our simplified conclusions are that, for the larger of the two search spaces we dealt with, the parallel version of the perfect rainbow table method gives the shortest wall-clock online time, and that, for the smaller search space, when restricted to the same amount of pre-computation, the perfect parallel DP tradeoff is faster than the other algorithms.Chapter 1 Introduction 1 Chapter 2 Preliminaries 7 2.1 Algorithm Clarification, Terminology, and Notation 7 2.1.1 Four Versions of the DP Tradeoff 8 2.1.2 Non-perfect and Perfect Rainbow Tradeoffs pR, p¯R 19 2.1.3 Perfect Rainbow Tradeoff, Used in Practice s¯R 25 2.1.4 Other Conventions and Comments 27 2.2 Storage Optimization Techniques 28 2.3 Previous Results 29 2.3.1 Analyses of the Original DP and Parallel DP Tradeoffs 30 2.3.2 Analysis of the Non-perfect Rainbow Tradeoff 31 Chapter 3 Perfect Table Tradeoff Algorithms 33 3.1 Analysis of the Perfect DP Tradeoff 33 3.1.1 Online Efficiency 33 3.1.2 Storage Optimization 46 3.1.3 Experiment Results 50 3.2 Analysis of the Perfect Rainbow Tradeoff 56 3.2.1 Online Efficiency 56 3.2.2 Storage Optimization 60 Chapter 4 Perfect Parallel DP Tradeoff 65 4.1 Online Efficiency 65 4.2 Storage Optimization 72 4.3 Experiment Results 75 Chapter 5 Comparisons Focused on Theoretical Complexities 85 5.1 Method of Comparison 86 5.2 Comparison of DP Variants 88 5.3 p¯D vs. Rainbow 92 Chapter 6 Practice-Oriented Comparison 100 6.1 Additional Costs for the p¯D and p¯R Tradeoffs 102 6.2 Analysis of the s¯R Tradeoff 103 6.3 Expressions for the Physical Online Time 104 6.4 How to Minimize the Physical Online Time 106 6.5 Comparisons 107 Chapter 7 Conclusion 116 Bibliography 119 Appendix A Practical System Constants τF, τL, and τH 123 A.1 tF 123 A.2 tL 125 A.3 tH 126 Abstract (in Korean) 129Docto

REVIEW: Current Status of Extenders and Cryoprotectants on Fish Spermatozoa Cryopreservation

An important component of many studies of cryopreservation of fish spermatozoa is the type of extenders and cryoprotectants. The suitability of extenders and cryoprotectants differs from one fish to another. There are many studies have been done in cryopreservation of fish spermatozoa. However, there are few review have been done. This review reveals some aspects of cryopreservation especially the role of extender and cryoprotectant in fish sperm cryopreservation. Fish produce high viscosity of sperm and in some cases only small volume is produced. Before cryopreserved in liquid nitrogen, sperm have to dilute with extenders and for long-term cryopreservation, cryoprotectants are needed to protect the sperm cell from cold and hot shock treatments and prevent cell dehydration during pre-freezing, freezing and post thawed. The suitability of extenders and cryoprotectants differs from one fish to another. Over the last decade, studies on the cryopreservation of mammalian sperm, animal husbandry sperm and human sperm have progressed significantly but studies on fish sperm is still confined to some aquatic

Factors affecting the pathogenicity of Yersinia ruckeri

A group of 42 strains of Yersinia ruckeri were characterized and found to show homogenous biochemical profiles. The optimal conditions for in vitro culture of a representative strain of Y. ruckeri were established. The virulence was increased by passage through fish. A standard method for infection of rainbow trout (Oncorhynchus mykiss) with Y. ruckeri was devised. As a result cultures of Y. ruckeri grown on full strength of BHIA for 5 h at 30°C in static conditions were found to be most suitable for infection by both intraperitoneal injection and immersion. Virulence of stored cultures was maintained for over 1 year at -20 and/or -70° C and virulence was not lost after up to six consecutive subcultures. The effect on mortality of susceptibility of various fish stocks, water temperature and stocking density is described. The size of fish (between 5 and 60 g) had no effect on virulence. The injection and immersion protocols were used as in vivo models for the study of the effects of dietary vitamin E, with both laboratory prepared diets and commercially available diets. Comparative results of haematological and biochemical parameters, histology, mortality patterns, serum antibody levels and bacterial recovery from the four dietary groups of fish are presented. A comparative in vitro and in vivo study of intra and inter strain vanations among representatives of the serogroup 1 of Y. ruckeri was performed. Under the conditions used, some strains were virulent and other avirulent. Results of Western blotting and SDS-PAGE showed the presence of a heat sensitive factor (HSF), present only in the virulent strains of Y. ruckeri. To date this is the first putative virulence factor described for Y. ruckeri. Further work was undertaken in an attempt to characterize the HSF. It appears to be located in the periplasmic space and to have complex lipid and proteinaceous components. HSF is easily degraded, and is immunogenic and confers some protection when injected into rainbow trout. Selective media and detection methods for the HSF, and their potential use in laboratory and field studies are described.The Ministry of Agriculture, Fisheries and Food, Weymouth, Englan

Deploying OSK on Low-Resource Mobile Devices

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI linkIt is a popular challenge to design authentication protocols that are both privacy-friendly and scalable. A large body of literature in RFID is dedicated to that goal, and many inventive mechanisms have been suggested to achieve it. However, to the best of our knowledge, none of these protocols have been tested so far in practical scenarios. In this paper, we present an implementation of the OSK protocol, a scalable and privacy-friendly authentication protocol, using a variant by Avoine and Oechslin that accommodates it to time-memory trade-offs. We show that the OSK protocol is suited to certain real-life scenarios, in particular when the authentication is performed by low-resource mobile devices. The implementation, done on an NFC-compliant cellphone and a ZC7.5 contactless tag, demonstrates the practicability and efficiency of the OSK protocol and illustrates that privacy-by-design is achievable in constrained environments

Using the Monsanto software

"March 1998."by John Ruark