In this thesis we study the notion of circular security for bit-encryption schemes. Informally speaking, a bit-encryption scheme is circular secure if it remains secure even if the key of the system is used to encrypt its own individual bits. This notion (or slight extensions thereof) has foundational applications, most notably in the context of fully-homomorphic encryption and amplification techniques for key dependent- message security. We explore the notion of circular security from three different perspectives, stemming from (1) assumptions sufficient to realize this notion, (2) minimal black-box assumptions on which this notion can be based and (c) applications of this notion when combined with other properties. Our main results are as follows: We give a construction of circular-secure public-key bit encryption based on any public-key encryption scheme that satisfies two special properties. We show that our constructed scheme besides circular security also offers two forms of key-leakage resilience. Our construction unifies two existing specific constructions of circular-secure schemes in the literature and also gives rise to the first construction based on homomorphic hash proof systems. We show that seed-circular-secure public-key bit-encryption schemes cannot be based on semantically-secure public-key encryption schemes in a fully-blackbox way. A scheme is seed-circular-secure if it allows for the bits of the seed (used to generate the public/secret keys) to be securely encrypted under the corresponding public key. We then extend this result to rule out a large and non-trivial class of constructions for circular security that we call key-isolating constructions. We give generic constructions of several fundamental cryptographic primitives based on a public-key bit-encryption scheme that combines circular security with a structural property called reproducibility. The main primitives that we build include families of trapdoor functions with strong security properties (i.e., one-wayness under correlated inputs), adaptive-chosen-ciphertext (CCA2) secure encryption schemes and deterministic encryption schemes. / Graduate / 0984

Homomorphic encryption has progressed rapidly in both efficiency and versatility since its emergence in 2009. Meanwhile, a multitude of pressing privacy needs --- ranging from cloud computing to healthcare management to the handling of shared databases such as those containing genomics data --- call for immediate solutions that apply fully homomorpic encryption (FHE) and somewhat homomorphic encryption (SHE) technologies. Recent rapid progress in fully homomorphic encryption has catalyzed renewed efforts to develop efficient privacy preserving protocols. Several works have already appeared in the literature that provide solutions to these problems by employing leveled or somewhat homomorphic encryption techniques. Here, we propose efficient ways of adapting the most fundamental programming problems; boolean algebra, arithmetic in binary and higher radix representation, sorting, and search to the fully homomorphic encryption domain by focusing on the multiplicative depth of the circuits alongside the more traditional metrics. The reduced depth allows much reduced noise growth and thereby makes it possible to select smaller parameter sizes in leveled FHE instantiations resulting in greater efficiency savings. We begin by exploring already existing solutions to these programming problems, and analyze them in terms of homomorphic evaluation and memory costs. Most of these algorithms appear to be not the best candidates for FHE solutions, hence we propose new methods and improvements over the existing algorithms to optimize performance.

University of Macau / Faculty of Science and Technology. / Department of Computer and Information Science

We explore quantum-resistant key establishment and hybrid encryption. We nd that while the discrete logarithm problem is e ciently solved by a quantum computer using Shor's algorithm, some instances are insecure even using classical computers. The discrete logarithm problem based on a symmetric group Sn is e - ciently solved in polynomial time. We design a PUF-based 4-round group key establishment protocol, adjusting the model to include a physical channel capable of PUF transmission, and modify adversarial capabilities with respect to the PUFs. The result is a novel group key establishment protocol which avoids computational hardness assumptions and achieves key secrecy. We contribute a hybrid encryption scheme by combining a key encapsulation mechanism (KEM) with a symmetric key encryption scheme by using two hash functions. We require only one-way security in the quantum random oracle model (QROM) of the KEM and one-time security of the symmetric encryption scheme in the QROM. We show that this hybrid scheme is IND-CCA secure in the QROM. We rely on a powerful theorem by Unruh that provides an upper bound on indistinguishability between the output of a random oracle and a random string, when the oracle can be accessed in quantum superposition. Our result contributes to the available IND-CCA secure encryption schemes in a setting where quantum computers are under adversarial control. Finally, we develop a framework and describe biometric visual cryptographic schemes generically under our framework. We formalize several security notions and de nitions including sheet indistinguishability, perfect indistinguishability, index recovery, perfect index privacy, and perfect resistance against false authentication. We also propose new and generic strategies for attacking e-BVC schemes such as new distinguishing attack, new index recovery, and new authentication attack. Our quantitative analysis veri es the practical impact of our framework and o ers concrete upper bounds on the security of e-BVC. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

by Wong Ha Yin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 71-74). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Traditional Payment Systems --- p.1 / Chapter 1.2 --- Electronic Payment System --- p.2 / Chapter 1.3 --- Thesis Organization --- p.4 / Chapter Chapter 2 --- Cryptographic Techniques --- p.5 / Chapter 2.1 --- Encryption and Decryption --- p.5 / Chapter 2.1.1 --- Symmetric Encryption --- p.6 / Chapter 2.1.2 --- Asymmetric or Public-Key Encryption --- p.6 / Chapter 2.2 --- RSA --- p.7 / Chapter 2.3 --- Blind Signatures --- p.8 / Chapter 2.4 --- General Computation Protocols --- p.8 / Chapter 2.5 --- Cut-and-Choose Method --- p.9 / Chapter 2.6 --- Hash Functions --- p.9 / Chapter 2.7 --- Secret Sharing --- p.10 / Chapter 2.8 --- Zero-Knowledge Proofs --- p.11 / Chapter 2.9 --- Timestamps --- p.12 / Chapter Chapter 3 --- Overview of Electronic Payment Systems --- p.13 / Chapter 3.1 --- Life Cycle --- p.13 / Chapter 3.2 --- Six Basic Requirements --- p.15 / Chapter 3.3 --- Efficiency --- p.16 / Chapter 3.4 --- History --- p.17 / Chapter Chapter 4 --- Ferguson's Single-term Off-Line Coins --- p.19 / Chapter 4.1 --- Basic Assumption and Tools --- p.19 / Chapter 4.1.1 --- Secure Hash Function --- p.19 / Chapter 4.1.2 --- Polynomial Secret Sharing Scheme --- p.20 / Chapter 4.1.3 --- Randomized Blind Signature --- p.21 / Chapter 4.2 --- The Basic Signal-term Cash System --- p.23 / Chapter 4.2.1 --- The Withdrawal Protocol --- p.24 / Chapter 4.2.2 --- The Payment Protocol --- p.26 / Chapter 4.2.3 --- The Deposit Protocol --- p.27 / Chapter Chapter 5 --- Cash with Different Denominations --- p.28 / Chapter 5.1 --- Denomination Bundling --- p.28 / Chapter 5.2 --- Coin Storage --- p.29 / Chapter Chapter 6 --- An Off-Line Transferable E-coin System --- p.32 / Chapter 6.1 --- Introduction --- p.32 / Chapter 6.2 --- The Withdrawal Protocol --- p.34 / Chapter 6.3 --- The Transfer / Payment Protocol --- p.36 / Chapter 6.4 --- The Deposit Protocol --- p.40 / Chapter 6.5 --- Expansion of Coins --- p.42 / Chapter 6.6 --- Security and privacy Analysis --- p.43 / Chapter 6.7 --- Complexity Analysis --- p.47 / Chapter 6.8 --- Conclusion --- p.49 / Chapter Chapter 7 --- A New Off-line E-check System --- p.50 / Chapter 7.1 --- Introduction --- p.50 / Chapter 7.2 --- E-checks Models --- p.51 / Chapter 7.3 --- E-Check System with Partial Privacy --- p.52 / Chapter 7.3.1 --- The Withdrawal Protocol --- p.52 / Chapter 7.3.2 --- The Payment Protocol --- p.55 / Chapter 7.3.3 --- The Deposit Protocol --- p.56 / Chapter 7.3.4 --- The Refund Protocol --- p.57 / Chapter 7.3.5 --- Protocol Discussion --- p.58 / Chapter 7.4 --- E-Check System with Unconditional Privacy --- p.59 / Chapter 7.4.1 --- The Withdrawal Protocol --- p.59 / Chapter 7.4.2 --- The Payment Protocol --- p.63 / Chapter 7.4.3 --- The Deposit Protocol --- p.64 / Chapter 7.4.4 --- The Refund Protocol --- p.65 / Chapter 7.4.5 --- Protocol Discussion --- p.67 / Chapter 7.5 --- Conclusion --- p.68 / Chapter Chapter 8 --- Conclusion --- p.69 / Reference --- p.71

by Lau Shek Kwan Mark. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 85-86). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Historical Background --- p.2 / Chapter 1.2 --- Introduction to Autostereograms --- p.5 / Chapter 1.2.1 --- Geometrical Model --- p.5 / Chapter 1.2.2 --- IS-separation --- p.6 / Chapter 1.2.3 --- The Hidden Surfaces --- p.7 / Chapter 1.2.4 --- False Target and Echo --- p.8 / Chapter 1.3 --- The Autostereogram Generation Algorithm --- p.10 / Chapter 1.4 --- Further Applications of Autostereograms --- p.15 / Chapter 1.5 --- Organization of Thesis --- p.17 / Chapter 2 --- Analysis of Autostereograms --- p.20 / Chapter 2.1 --- IS-separation --- p.21 / Chapter 2.2 --- Autostereogram Generations --- p.25 / Chapter 2.3 --- Surface Reconstructions --- p.26 / Chapter 2.4 --- Visual Distortions --- p.28 / Chapter 2.4.1 --- Problem Model For Vertical Distortions --- p.30 / Chapter 2.4.2 --- Change of Depth Field --- p.33 / Chapter 2.4.3 --- Non-linear Distortion --- p.35 / Chapter 2.4.4 --- Lateral Distortions --- p.38 / Chapter 2.5 --- Discrete Autostereograms --- p.40 / Chapter 2.5.1 --- Truncation Problem --- p.41 / Chapter 2.5.2 --- Computer Algorithms for Autostereograms --- p.42 / Chapter 3 --- Analysis of Echoes --- p.48 / Chapter 3.1 --- Causes of Echoes --- p.49 / Chapter 3.1.1 --- Insufficient Lengths of The Periods of Repeating Patterns --- p.51 / Chapter 3.1.2 --- Overlapping of Copying Steps --- p.51 / Chapter 3.2 --- Avoidance of Type 1 Echoes --- p.52 / Chapter 3.3 --- Avoidance of Type 2 Echoes --- p.55 / Chapter 3.4 --- Autostereogram Encoding Any Surface --- p.58 / Chapter 4 --- Autostereogram as A Cryptosystem --- p.65 / Chapter 4.1 --- Introduction to Cryptography --- p.66 / Chapter 4.1.1 --- Mathematical Structure of Cryptosystems --- p.67 / Chapter 4.1.2 --- A Classical Cryptosystem´ؤSubstitution Cipher --- p.68 / Chapter 4.2 --- Autostereogram as a Cryptosystem --- p.72 / Chapter 4.2.1 --- Autostereogram as a Variation of Substitution Cipher --- p.74 / Chapter 4.2.2 --- Practical Considerations --- p.76 / Chapter 5 --- Conclusion and Future Works --- p.79 / Chapter 5.1 --- Future Works --- p.80 / Chapter A --- Excessive Removal of Copying Steps --- p.81 / Chapter B --- Publications Resulted from the Study --- p.84

Lee, Chin Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 77-82). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese.

In the past decade, one of the major breakthroughs in computer science theory is the first construction of fully homomorphic encryption (FHE) scheme introduced by Gentry. Using a FHE one may perform an arbitrary numbers of computations directly on the encrypted data without revealing of the secret key. Therefore, a practical FHE provides an invaluable security application for emerging technologies such as cloud computing and cloud-based storage. However, FHE is far from real life deployment due to serious efficiency impediments. The main part of this dissertation focuses on accelerating the existing FHE schemes using GPU and hardware design to make them more efficient and practical towards real-life applications. Another part of this dissertation is for the hardware design of the large key-size RSA cryptosystem. As the Moore law continues driving the computer technology, the key size of the Rivest-Shamir-Adelman (RSA) encryption is necessary to be upgraded to 2048, 4096 or even 8192 bits to provide higher level security. In this dissertation, the FFT multiplication is employed for the large-size RSA hardware design instead of using the traditional interleaved Montgomery multiplication to show the feasibility of the FFT multiplication for large-size RSA design.

Siu, Pui-Lam. / Thesis submitted in: August 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 104-109). / Abstracts in English and Chinese. / list of figures --- p.5 / list of tables --- p.7 / acknowledgements --- p.8 / abstract --- p.9 / Chapter 1. --- introduction --- p.12 / Chapter 1.1 --- Smart Card --- p.12 / Chapter 1.1.1 --- What is a smart card? --- p.12 / Chapter 1.1.2 --- How is a smart card different from the magnetic stripe card that I carry in my wallet? --- p.13 / Chapter 1.1.3 --- Why are interoperability and enforced standards crucial to widespread adoption of smart cards? --- p.13 / Chapter 1.1.4 --- Contact vs Contactless --- p.14 / Chapter 1.1.5 --- How secure and confidential contactless smart cards are? --- p.14 / Chapter 1.1.6 --- Contactless Smart Card Application Contactless smart cards are widely used in commercial fields as stored-value and secure storage cards --- p.14 / Chapter 1.1.7 --- What are the major benefits that Contactless smart cards offer to consumers? --- p.16 / Chapter 1.2 --- Design Motivation --- p.16 / Chapter 1.3 --- RF Part Interface --- p.17 / Chapter 1.4 --- Potential Advantages of Using Asynchronous Circuit --- p.19 / Chapter 1.5 --- Design Methodology for Asynchronous Circuit --- p.23 / Chapter 1.5.1 --- Difficulty and limitation of asynchronous design --- p.27 / Chapter 1.5.2 --- Asynchronous pipeline --- p.28 / Chapter 2. --- background theory --- p.32 / Chapter 2.1 --- Description of DES --- p.32 / Chapter 2.1.1 --- Outline of the Algorithm --- p.33 / Chapter 2.1.2 --- Initial Permutation --- p.35 / Chapter 2.1.3 --- Key Transformation --- p.35 / Chapter 2.1.4 --- Expansion Permutation --- p.37 / Chapter 2.1.5 --- S-box Substitution --- p.38 / Chapter 2.1.6 --- P-Box Permutation --- p.41 / Chapter 2.1.7 --- Final Permutation --- p.42 / Chapter 2.1.8 --- Decrypting DES --- p.43 / Chapter 2.1.9 --- Security of DES --- p.43 / Chapter 2.1.10 --- Weak Keys --- p.43 / Chapter 2.1.11 --- Algebraic Structure --- p.46 / Chapter 2.1.12 --- Key Length --- p.46 / Chapter 2.1.13 --- Number of Rounds --- p.48 / Chapter 2.1.14 --- Design of the S-Boxes --- p.48 / Chapter 3. --- rf part --- p.50 / Chapter 3.1 --- Power On --- p.51 / Chapter 3.2 --- Power Induction --- p.52 / Chapter 3.3 --- Limiter and Regulator --- p.54 / Chapter 3.4 --- Demodulation --- p.56 / Chapter 3.5 --- Modulation --- p.57 / Chapter 4. --- asynchronous circuit theory --- p.58 / Chapter 4.1 --- Potential Problem of Classical Asynchronous Pipeline --- p.58 / Chapter 4.2 --- The New Handshake Cell --- p.58 / Chapter 4.3 --- The Modified Asynchronous Pipeline Architecture --- p.60 / Chapter 4.4 --- Asynchronous Circuit Comparison --- p.65 / Chapter 5 --- implementation --- p.67 / Chapter 5.1 --- DES Implementation --- p.67 / Chapter 5.1.1 --- Power estimation of the asynchronous DES --- p.70 / Chapter 5.1.2 --- Modified Circuit --- p.73 / Type One --- p.73 / Type two --- p.76 / Chapter 5.1.3 --- Interface --- p.79 / Chapter 5.1.4 --- Shift Unit --- p.80 / Chapter 5.1.5 --- Multiplexer Unit --- p.82 / Chapter 5.1.6 --- Compression Unit --- p.83 / Chapter 5.1.7 --- Expansion Unit --- p.84 / Chapter 5.1.8 --- Xor Unit --- p.85 / Chapter 5.1.9 --- S_box Unit --- p.86 / Chapter 5.1.10 --- P-box unit --- p.88 / Chapter 5.1.11 --- Latch unit --- p.89 / Chapter 5.1.12 --- Transmission Unit --- p.90 / Chapter 5.2 --- Floor Plan Design --- p.90 / Chapter 6. --- result and discussion --- p.93 / Chapter 6.1 --- Simulation Result --- p.93 / Chapter 6.2 --- Measurement --- p.97 / Chapter 6.3 --- Comparison --- p.101 / Chapter 6.4 --- Conclusion --- p.101 / Chapter 7. --- reference --- p.104 / Chapter 8. --- appendix --- p.110 / Chapter 8.1 --- RF Part Implementation --- p.110 / Chapter 8.1.1 --- Full wave rectifying circuit --- p.110 / Chapter 8.1.2 --- "Limiting Circuit," --- p.111 / Chapter 8.1.3 --- Regulator circuit --- p.113 / Chapter 8.1.4 --- Demodulation circuit --- p.113 / Chapter 8.1.5 --- Simulation of the RF part --- p.115 / Chapter 8.2 --- New Technology for Designing a RF Interface --- p.117 / Chapter 8.2 --- Block Diagrams --- p.118

In The Second Theory of Cryptography Conference (TCC 2005), Boneh, Goh, and Nissim proposed a new structure of bilinear groups that have a composite order and a new cryptosystem which is intractable on a decisional problem over the subgroup in such structure [BGN05]. Their proposal, which referred to as the BGN cryptosystem by researchers, receive much attention and is quickly followed by two publications in CRYPTO'05 [BI05, OI05]. / In this thesis, the author performs in-depth study of the BGN public-key cryptosystem and existing literatures on its applications. The author observes two properties of BGN, namely the indistinguishability of the BGN ciphertexts of sum and product of two messages, and the verifiability of elements from composite prime subgroups in BGN settings. The author further proposes three new applications of BGN, namely the protocols for authentication, oblivious transfer, and proof-of-visit respectively. / The BGN cryptosystem is a dual homomorphic public-key cryptosystem that enables the evaluation of 2-DNF (disjunctive normal form) formulas on ciphertexts. In their work, Boneh et. al. also presented three applications, namely private information retrieval with reduced computational complexity, an e-voting system without non-interactive zero knowledge proofs, and a protocol for universally verifiable computation. Few number of works also produced from the BGN public-key system, include non-interactive zero-knowledge proof (NIZK), obfuscated ciphertext mixing, and signature. / Chan Yuen Yan. / "June 2006." / Adviser: Victor K. Wei. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6498. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 85-100). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.