The Zero-Knowledge Proof(ZKP)is a powerful tool which can be used and already be used for many cryptographic applications and E-Commerce.But all existing Zero-Knowledge Proofs are iterative in nature,it increases the communication traffic of in interactive bilateral,and makes difficult in practice.This thesis proposes a new ZKP protocol which runs in one-round while ensure the completeness property,and the soundness property,and decreases the communication traffic in the maximum extent.The scheme is based on the Paillier Cryptosystem,and ascribes security to it.
Decentralization is a mechanism by means of which the local administration authorities receive the authority and the resources allowing them to make decisions concerning the provision of public services. The balancing of the local budgets in Romania is the consequence of the financial decentralization, according to which the local communities were entrusted with/allotted their responsibilities and then they were entrusted with/allotted their resources as well. The separation of the attributions of the central and of the local administration conditions the way the revenues and the expenses were distributed between the two levels. This process depends on the degree of regional development, on the concentration of the population on its welfare degree, on the tasks each community has to face, on the possibility of financing the foreseen expenses from local resources.
This paper presents a new zero-knowledge protocol for SDH pair(A,a),which is based on Chik How Tan encryption,then we prove that the protocol is an honest verifier zero knowledge proof of knowledge under DBDH assumption.The protocol is suitable for users with higher requirements for data security.Compared with[6],the protocol is of higher efficiency.
This paper deals with efficient non-malleable zero-knowledge proofs forNP, based on general assumptions. We construct a simulation-sound zero-knowledge (ZK) protocol for NP, based only on the black-box use of one-way functions. Constructing such a proof system has been an open question ever since the original work of Dolev, Dwork, and Naor [DDN91]. In addition to the feasibility result, our protocol has a constant number of rounds, which is asymptotically optimal. Traditionally, the term non-malleable zero-knowledge (NmZK) refers to the original definition of [DDN91]; but today it is used loosely to also refer to simulation-soundness (SimSound) [Sah99], and simulation-extractability (SimExt) [PR05b]. While SimExt implies NmZK, the common perception is that SimExt is strongest of the three notions. A formal study of the definitional relationship between these three notions, however, has never been done. In the second part of this work, we try to correct this situation by initiating such a study. We show that in the “static” case, if an NmZK protocol is also an argument-of-knowledge, then it is in fact SimExt. Furthermore, in the most strict sense of the definition, SimSound does not necessarily follow from SimExt. These results are somewhat surprising because they are opposite to the common perception that SimExt is the strongest of the three notions.
We present new candidates for quantum-resistant public-key cryptosystems based on the conjectured difficulty of finding isogenies between supersingular elliptic curves. The main technical idea in our scheme is that we transmit the images of torsion bases under the isogeny in order to allow the parties to construct a shared commutative square despite the noncommutativity of the endomorphism ring. Our work is motivated by the recent development of a subexponential-time quantum algorithm for constructing isogenies between ordinary elliptic curves. In the supersingular case, by contrast, the fastest known quantum attack remains exponential, since the noncommutativity of the endomorphism ring means that the approach used in the ordinary case does not apply. We give a precise formulation of the necessary computational assumptions along with a discussion of their validity, and prove the security of our protocols under these assumptions. In addition, we present implementation results showing that our protocols are multiple orders of magnitude faster than previous isogeny-based cryptosystems over ordinary curves. This paper is an extended version of [19]. We add a new zero-knowledge identification scheme, and detailed security proofs for the protocols. We also present a new, asymptotically faster, algorithm for key generation, a thorough study of its optimization, and new experimental data.
The paper presents the current state of the process of agencification in Croatia, pointing out both the process and the institutional design. The agency model in Croatia consists of several types of more or less autonomous administrative organizations, situated at different distances from the central government. The most evident pressures for agencification come from decentralization, managerial responses and Europeanization. The reversal of the process in recent years has mostly happened because of the need for rationalization of the public administration system, which is also under pressure because of the economic crisis. The key problems of the agency model are over politicization on the one hand, and insufficient and inadequate control on the other. The adequate legal framework for agencies would enhance institutionalization of the agency model, ensuring effectiveness and legal certainty and maintaining a sufficient level of independence.
We present a method to compile Yao’s two-player garbled circuit protocol into one that is secure against malicious adversaries that relies on witness indistinguishability. Our approach can enjoy lower communication and computation overhead than methods based on cut-andchoose [13] and lower overhead than methods based on zero-knowledge proofs [8] (or Σ-protocols [14]). To do so, we develop and analyze new solutions to issues arising with this transformation: — How to guarantee the generator’s input consistency — How to support different outputs for each player without adding extra gates to the circuit of the function f being computed — How the evaluator can retrieve input keys but avoid selective failure attacks — Challenging 3/5 of the circuits is near optimal for cut-and-choose (and better than challenging 1/2) Our protocols require the existence of secure-OT and claw-free functions that have a weak malleability property. We discuss an experimental implementation of our protocol to validate our efficiency claims.
Sanjam Garg, Rafail Ostrovsky, Ivan Visconti, Akshay Wadia
Abstract Two central notions of Zero Knowledge that provide very strong, yet seemingly incomparable security guarantees against malicious verifiers are those of Statistical Zero Knowledge and Resettable Zero Knowledge. The current state of the art includes several feasibility and impossibility results about the two notions separately. However, the challenging question of achieving Resettable Statistical Zero Knowledge (i.e., Resettable Zero Knowledge and Statistical Zero Knowledge simultaneously) for non-trivial languages is still open. In this paper, we show:- Resettable Statistical Zero Knowledge with efficient provers: Efficient-prover Resettable Statistical Zero-Knowledge proof systems exist for all languages that admit hash proof systems (e.g., QNR, QR, DDH, DCR). Furthermore, for these languages, as an application of our technique, we also construct a two-round resettable statistical witness-indistinguishable argument system.- Resettable Statistical Zero Knowledge with unbounded provers: Under the assumption that sub-exponentially hard one-way functions exist, rSZK = SZK. In other words, every language that admits a Statistical Zero-Knowledge (SZK) proof system also admits a Resettable Statistical Zero-Knowledge (rSZK) proof system. (Further, the result can be re-stated unconditionally provided there exists a sub-exponentially hard language in SZK). Moreover, under the assumption that (standard) one-way functions exist, all languages L such that the complement of L is random self reducible, admit a rSZK, in other words: co-RSR ⊆ rSZK. The round complexity of all our proof systems is Õ(log κ), where κ is the security parameter, and all our simulators are black-box. 1
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Developing countries are facing a great challenge to collect, treat and dispose their waste in a more sustainable way. Today, most of the produced waste ends up on landfills, where they pose a great threat to the environment and human health. Kumasi, the second largest city in Ghana, faces the same issues as other cities in developing countries; waste management is run poorly and most waste ends up on the cities largest landfill, Dompoase, which will be full in a few years time. Issues such as low financial resources, bad urban planning and a growing population aggravate the implementation of a more sustainable development. Since most solid waste in developing countries is organic, composting is a good option towards a more sustainable waste management. There are numerous amounts of articles stating that decentralized composting is the best option for developed countries. Decentralized compost facilities are less costly to install and maintain, they require less technology and decrease the cost of waste transportation. Transportation poses a large expense when it comes to waste management in developing countries. There is an advantage in integrating a more sustainable waste management in to the existing waste infrastructure since cities often are densely built up and there is a shortage of land. Therefore this thesis has investigated the possibilities of having waste sorting stations and decentralized compost facilities at public dumping sites in the Bantama area, one of ten sub--‐metros in Kumasi. Based on literature and observations during field visits in the Bantama area, a classification scheme was developed. The classification scheme was designed to simplify identification and differentiation of the sites. It contains thirteen criteria to consider when planning for organic waste sorting stations and decentralized compost facilities. Suitable sites for sorting stations and decentralized compost facilities were selected by a SQL analyzes in a Geographic Information System (GIS). The analyzes was based on the classification scheme. The result shows that of twenty--‐one public dumpingsites, seven were suitable as sorting stations and two sites were suitable for a decentralized compost facility. The expectation is that in due time and with infrastructure improvements, more than only seven communal sites can become sorting stations. When it comes to sites for composting the result reveals an issue in many cities there is just not enough land to build as many decentralized facilities as would be necessary to recycle all organic waste. However, due to the advantages of having decentralized facilities, the recommendation is that Kumasi should start with a decentralized approach and as finance and technological skills exists the organic waste management can extend to also include larger facilities. Further this thesis shows the advantage of having decentralized composting when it comes totransportation costs. A transport analyzes was done in a GIS, which showed the difference intransportation distances between having decentralized and centralized composting. The result showed that waste recycled close to its source, i.e. having decentralized waste management, is transported shorter distance compared to having centralized composting and thus saving on cost for transportation.
A mobile ad hoc network is an autonomous system connected through wireless links. It does not have any fixed infrastructure, and the mobile nodes in the network coordinate among themselves for communication. This network can be formed by heterogeneous mobile devices like laptops, PDAs, cell phones etc. Highly capable device provides some services to low capability device and this will bring in a grid environment into the mobile ad hoc networks. A balanced allocation of load is a critical issue in such grids, considering its limitations in terms of power and availability. A decentralized approach is favored for a dispersed functioning of the grid, without draining a single chosen node. It is also essential to augment the resource allocation with an effective authorization mechanism, as the ad hoc grids lack permanent trusted central authority. In this paper, dynamic virtual organizations are constructed within this grid based on the resource commonalities of devices. Upon this setup we implement a decentralized load balancing mechanism that is able to perform a d ynamic load balancing among nodes within a VO i.e. intra-VO load balancing using the Local Load Balancing Algorithm and also between the dynamic VOs i.e. inter-VO load balancing using the Global Load Balancing Algorithm for efficient utilization of resources and enhancing the performance of computational grid. When jobs are sent across VOs due to resources unavailability within its own VO, a trust check is performed based on t he intersection trust factor between the VOs. The effectiveness of the algorithm is substantiated by the simulation results.
Abstract. Zero-knowledge proofs of knowledge (ZK-PoK) for discrete logarithms and related problems are indispensable for practical cryptographic protocols. At Eurocrypt 2009, Camenisch, Kiayias, and Yung provided a specification language (the CKY-language) for such protocols, which allows one to modularly design and analyze cryptographic protocols: protocol designers just need to specify the statement they want to prove in zero-knowledge and are ensured that an efficient proof protocol exists and indeed proves the specified statement, provided that the specification was in the CKY-language. However, as specifications in the CKY-language are realized by so-called Σ-protocols, the resulting protocols only satisfy the classical notion of zero-knowledge proofs of knowledge, which not retained if they are composed with themselves or with other protocols, e.g., when used as building blocks for higher-level applications. This problem can be tackled by moving to the Universal Composability (UC) framework, which guarantees retention of security when composing protocols and, in particular, when using them as building blocks in arbitrary contexts. While there exists generic transformations from Σ-protocols to protocols that are secure under this stronger security notion, these transformation are often not efficient enough for the design of practical protocols. In this paper we are aiming for practically efficient ZK-PoK in the UC-framework by introducing
Graham Busby, Maximiliano E. Korstanje, Charlie Mansfield
This study selects novels from French and Spanish language traditions, which may not be available to English-speakers, in order to determine if specific aspects throw light on our understanding of Madrid as a destination. Marc Lambron's L'Impromptu de Madrid and Antonio Munoz Molina’s Mysteries of Madrid are taken as proof of the influence the narrative can exert on social daily life and consumption. Narrative foregrounds the fictions which are at stake in imagining the city as destination and also provides a vehicle for presenting the much broader social forces that converge in the author at the time of imagining and writing.