Public key encryption plays a vital role in securing sensitive data in practical applications. The security of many encryption schemes relies on mathematical problems related to the difficulty of factoring large integers. In particular, subgroup problems in composite order groups are a general class of problems widely used in the construction of secure public-key encryption schemes. This thesis studies public-key encryption schemes that are provably secure based on the difficulty of subgroup or other integer factorisation related problems in the standard model. Firstly, a number of new public-key encryption schemes are presented which are secure in the sense of indistinguishability against chosen-ciphertext attack in the standard model. These schemes are obtained by instantiating the two previous paradigms for chosen-ciphertext security by Cramer and Shoup, and Kurosawa and Desmedt, with three previously studied subgroup membership problems. The resulting schemes are very efficient, and are comparable if not superior in terms of efficiency when compared to previously presented instantiations. Secondly, a new approach is presented for constructing RSA-related public key encryption schemes secure in the sense of indistinguishability against chosenciphertext attack without random oracles. This new approach requires a new set of assumptions, called the Oracle RSA-type assumptions. The motivating observation is that RSA-based encryption schemes can be viewed as tag-based encryption schemes, and as a result can be used as a building block in a previous technique for obtaining chosen-ciphertext security. Two example encryption schemes are additionally presented, each of which is of comparable efficiency to other public key schemes of similar security. Finally, the notion of self-escrowed public-key infrastructures is revisited, and a security model is defined for self-escrowed encryption schemes. The security definitions proposed consider adversarial models which reflect an attacker's ability to recover private keys corresponding to public keys of the attacker's choice. General constructions for secure self-escrowed versions of ElGamal, RSA, Cramer-Shoup and Kurosawa-Desmedt encryption schemes are also presented, and efficient instantiations are provided. In particular, one instantiation solves the 'key doubling problem' observed in all previous self-escrowed encryption schemes. Also, for another instantiation a mechanism is described for distributing key recovery amongst a number of authorities.

本文主要研究分析日本在第二次世界大戰以後，根據美國蕭普(Shoup) 顧問團之建議 、所改革、確立的地方財政制度內容。 第一章為序論、並說明日本戰後之政治體制，與地方公共團體類別。 第二章、討論日本的中央財政與地方財政的各種關係。 第三章、說明日本地方財政的支出結構及其演變。 第四章、說明日本地方財政的收入結構。 第五章、討論日本地方財政的調整制度。 第六章、研究日本地方財政近年來所發生的各種問題，及其對策。 第七章、結論。

This thesis primarily focuses on the electrochemical properties of the H₂/H⁺ redox couple, at various metallic electrodes in room temperature ionic liquids. Initially, a comprehensive overview of room temperature ionic liquids, RTILs, compared to conventional organic solvents is presented which identifies their favourable properties and applications, followed by a second chapter describing the basic theory of electrochemistry. A third chapter presents the general experimental reagents, instruments and measurements used in this thesis. The results presented in this thesis are summarized in six further chapters and shown as follows. (1) Hydrogenolysis, hydrogen loaded palladium electrodes by electrolysis of H[NTf₂] in a RTIL [C₂mim][NTf₂]. (2) Palladium nanoparticle-modified carbon nanotubes for electrochemical hydrogenolysis in RTILs. (3) Electrochemistry of hydrogen in the RTIL [C₂mim][NTf₂]: dissolved hydrogen lubricates diffusional transport. (4) The hydrogen evolution reaction in a room temperature ionic liquid: mechanism and electrocatalyst trends. (5) The formal potentials and electrode kinetics of the proton_hydrogen couple in various room temperature ionic liquids. (6) The electroreduction of benzoic acid: voltammetric observation of adsorbed hydrogen at a Platinum microelectrode in room temperature ionic liquids. The first two studies show electrochemically formed adsorbed H atoms at a metallic Pt or Pd surface can be used for clean, efficient, safe electrochemical hydrogenolysis of organic compounds in RTIL media. The next study shows the physicochemical changes of RTIL properties, arising from dissolved hydrogen gas. The last three studies looked at the electrochemical properties of H₂/H⁺ redox couple at various metallic electrodes over a range of RTILs vs a stable Ag/Ag⁺ reference couple, using H[NTf₂] and benzoic acid as proton sources. The kinetic and thermodynamic mechanisms of some reactions or processes are the same in RTILs as in conventional organic or aqueous solvents, but other remarkably different behaviours are presented. Most importantly significant constants are seen for platinum, gold and molybdenum electrodes in term of the mechanism of proton reduction to form hydrogen.