New Representative Collective Signatures Based on the Discrete Logarithm Problem

The representative collective digital signature scheme allows the creation of a unique collective signature on document M that represents an entire signing community consisting of many individual signers and many different signing groups, each signing group is represented by a group leader. On document M, a collective signature can be created using the representative digital signature scheme that represents an entire community consisting of individual signers and signing groups, each of which is represented by a group leader. The characteristic of this type of letter is that it consists of three elements (U, E, S), one of which (U) is used to store the information of all the signers who participated in the formation of the collective signature on document M. While storing this information is necessary to identify the signer and resolve disputes later, it greatly increases the size of signatures. This is considered a limitation of the collective signature representing 3 elements. In this paper, we propose and build a new type of collective signature, a collective signature representing 2 elements (E, S). In this case, the signature has been reduced in size, but it contains all the information needed to identify the signer and resolve disputes if necessary. To construct the approved group signature scheme, which is the basic scheme for the proposed representative collective signature schemes, we use the discrete logarithm problem on the prime finite field. At the end of this paper, we present the security analysis of the AGDS scheme and a performance evaluation of the proposed collective signature schemes.     

New Collective Signatures Based on the Elliptic Curve Discrete Logarithm Problem

There have been many digital signature schemes were developed based on the discrete logarithm problem on a finite field. In this study, we use the elliptic curve discrete logarithm problem to build new collective signature schemes. The cryptosystem on elliptic curve allows to generate digital signatures with the same level of security as other cryptosystems but with smaller keys. To extend practical applicability and enhance the security level of the group signature protocols, we propose two new types of collective digital signature schemes based on the discrete logarithm problem on the elliptic curve: i) the collective digital signature scheme shared by several signing groups and ii) the collective digital signature scheme shared by several signing groups and several individual signers. These two new types of collective signatures have combined the advantages of group digital signatures and collective digital signatures. These signatures have a fixed size and do not depend on the number of members participating in the creation of the final collective signature. One of the advantages of the proposed collective signature protocols is that they can be deployed on top of the available public key infrastructures.     

An anonymous buyer‐reseller watermarking protocol

Abstract

In (Memon and Wong, 2001), Memon and Wong first proposed a buyer‐seller watermarking protocol. Inspired by (Memon and Wong, 2001), Cheung and Curreem recently proposed a buyer‐reseller watermarking protocol to address the digital contents redistribution in the second‐hand markets over the Internet (Cheung and Curreem, 2002). In this paper, we show that their watermarking protocol is vulnerable to malicious attacks and propose a simple improvement. The main contribution is that we extend their schemes to enable anonymous transactions among a buyer, a reseller, and a seller in order to further protect the privacy of the buyers.     

Improving a supplier's quantity discount gain from many different buyers

We consider the pricing and inventory decisions of a vendor who supplies a single product to multiple heterogeneous buyers. The problem is analyzed as a Stackelberg game in which the vendor acts as the leader by announcing its pricing policy to all the buyers in advance and the buyers act as followers by choosing their order quantity and the sassociated purchasing price independently under the vendors' pricing scheme. We propose in this paper a pricing policy for the vendor that offers price discounts based on the percentage increase from a buyers' order quantity before discount. The proposed policy is defined as a discrete all-unit quantity discount schedule with many break points. We show that: (i) the proposed policy offers a higher price discount to a buyer ordering a larger quantity and hence complies with general fair trade laws; (ii) an explicit solution is obtained for the vendors' optimal decision; and (iii) although suppliers in reality normally offer price discounts based on a buyers' unit increase in order quantity, the proposed policy is superior for the vendor when there are many different buyers. Other benefits of the proposed pricing policy are demonstrated by numerical examples.     

Code-based Sequential Aggregate Signature Scheme

This paper proposes the first code-based quantum immune sequential aggregate signature (SAS) scheme and proves the security of the proposed scheme in the random oracle model. Aggregate signature (AS) schemes and sequential aggregate signature schemes allow a group of potential signers to sign different messages respectively, and all the signatures of those users on those messages can be aggregated into a single signature such that the size of the aggregate signature is much smaller than the total size of all individual signatures. Because of the aggregation of many signatures into a single short signature, AS and SAS schemes can reduce bandwidth and save storage; moreover, when a SAS is verified, not only the valid but also the order in which each signer signed can be verified. AS and SAS schemes can be applied to traffic control, banking transaction and military applications. Most of the existing AS and SAS schemes are based either on pairing or Rivest–Shamir–Adleman (RSA), and hence, can be broken by Shor’s quantum algorithm for Integer Factoring Problem (IFP) and Discrete Logarithm Problem (DLP). There are no quantum algorithms to solve syndrome decoding problems. Hence, code-based cryptography is seen as one of the promising candidates for post-quantum cryptography. This paper shows how to construct quantum immune sequential aggregate signatures based on coding theory. Specifically, we construct our scheme with the first code based signature scheme proposed by Courtois, Finiasz and Sendrier (CFS). Compared to the CFS signature scheme without aggregation, the proposed sequential aggregate signature scheme can save about 90% storage when the number of signers is asymptotically large.     

A two-way approach to supply chain partner selection

All organisations face partner selection. It is the first step in establishing partnership. Over recent decades, a one-way selection approach has been dominant in the literature. It is assumed that a buyer searches for one or more suppliers from a set of suppliers. Once the best supplier is found and selected, a partnership is formed. However, in reality, not only is the selection not a one-way process as the relationship itself is bilateral, but the existence of other buyers and suppliers also needs to be taken into account. In this study, a two-way partner selection approach is proposed, where not only the buyers evaluate suppliers, but also the suppliers have the opportunity to evaluate buyers. Considering a marketplace where there are several buyers and suppliers, an integrative model is proposed in the form of an assignment model to optimally match all the buyers and suppliers. A generalised model is also formulated to take the suppliers’ capacity and buyers’ demand into account. The proposed models are illustrated using some numerical examples. Finally, conclusions and recommendations for future research are provided.     

A multi-attribute multi-item negotiation mechanism of supply chain networks between buyers and sellers

This article focuses on the multi-attribute multi-item negotiation between multiple manufacturer agents (MAs) and multiple material supplier agents (MSAs). A coalition formation-based negotiation protocol is proposed. The MSAs are allowed to establish coalitions when the orders of the MAs exceed their abilities. Three attributes (price, quantity and lead time) of the items are considered during the negotiation. Both the MAs and the MSAs can give concessions among the attributes in tradeoff relationships according to their own preferences. The non-cooperative game is introduced to find the equilibria of the negotiations. The final allocation scheme is determined to maximise the total profit of the supply chain networks based on the equilibria. Simulations are provided to verify the effectiveness and feasibility of the proposed protocol.     

An augmented Lagrangian algorithm for contact mechanics based on linear regression

The penalty method for the solution of contact problems yields an approximate satisfaction of the contact constraints. Augmentation schemes, which can be adopted to improve the solution, either include the contact forces as additional unknowns or are strongly affected by the penalty parameter and display a poor convergence rate. In a previous investigation, an unconventional augmentation scheme was proposed, on the basis of estimating the ‘exact’ values of the contact forces through linear interpolation of a database extracted by the previous converged states. An enhanced version of this method is proposed herein. With respect to the original method, the enhanced one eliminates some numerical problems and improves the regularity of the convergence path by carrying out the estimate through linear regression methods. The resulting convergence rate is superlinear, and the method is quite insensitive to the penalty parameter. The main underlying concept is that, within the iterative solution of a non‐linear problem, linear regression techniques may be used as a tool to ‘shoot’ faster to the final solution, on the basis of a set of intermediate data. The generality of this concept makes it potentially applicable to contact problems in more general settings, as well as to other categories of non‐linear problems. Copyright © 2012 John Wiley & Sons, Ltd.     

Collaborating freight forwarding enterprises

The paper presents a model for the collaboration among independent freight forwarding entities. In the modern highly competitive transportation branch freight forwarders reduce their fulfillment costs by exploiting different execution modes (self-fulfillment and subcontraction). For self-fulfillment they use their own vehicles to execute the requests and for subcontracting they forward the orders to external freight carriers. Further enhancement of competitiveness can be achieved if the freight forwarders cooperate in coalitions in order to balance their request portfolios. Participation in such a coalition gains additional profit for the entire coalition and for each participant, therefore reinforcing the market position of the partners. The integrated operational transport problem as well as existing collaboration approaches are introduced. The presented model for collaboration is based on theoretical foundations in the field of combinatorial auctions and operational research game theory. It is applicable for coalitions of freight forwarders, especially for the collaboration of Profit Centres within large freight forwarding companies. The proposed theoretical approach and the presented collaboration model are suitable for a coalition of freight forwarding companies with nearly similar potential on the market.     

A fuzzy AHP evaluation model for buyer–supplier relationships with the consideration of benefits,opportunities, costs and risks

With increasingly fierce global competition, firms in various industries need to build a cooperative buyer–supplier relationship to survive and to acquire reasonable profit. Even though the literature on various types of collaboration between firms is abundant and the works on supplier selection models are numerous, the research that provides a mathematical model for the selection of the most appropriate form of buyer–supplier relationship is very limited. Existing buyer–supplier evaluation models usually only consider the benefits from the relationship, but not the opportunities, costs and risks that may need to be confronted. The main objective of this study is to propose an analytical approach to evaluate the forms of buyer–supplier relationship between a manufacturer and its supplier. A fuzzy analytic hierarchy process (AHP) model, which applies fuzzy set theory and the benefits, opportunities, costs and risks (BOCR) concept, is constructed to deal with uncertainty and to consider various aspects of alternatives. Multiple factors that affect the success of the relationship are analysed by incorporating experts’ opinions on their priority of importance, and a performance ranking of the buyer–supplier forms is obtained. A case study of selecting the most appropriate buyer–supplier form between a TFT-LCD manufacturer and its colour filter supplier is presented, and the proposed model is applied to facilitate the decision process. The proposed model is a general form that can be tailored and applied by firms that are making decisions on buyer–supplier relationship.     

Co-procurement: making the most of collaborative procurement

While the procurement decision is generally made by individual buyers, this study investigates how a group of buyers can make a shared decision. We call this collaborative approach, co-procurement. A mathematical model is formulated for the decision of procurement from multiple suppliers. The model is solved for individual buyers. The outcome shows the optimal number of items a buyer should buy from different suppliers such that the total cost is minimised for that buyer. Next, it is investigated how a group of buyers could make this decision together. The proposed model takes into account transaction costs of collaboration, to determine the optimal size of the collaboration and the involved parties. The idea is new in the old direction of procurement and it introduces the concept of transaction costs in this area and analyses its impact on the optimal collaboration size and mix. A case study from Dutch Food Valley is provided to investigate the benefits of co-procurement and validate the developed structure. The results indicate that co-procurement can bring considerable cost-savings through consolidation of orders and more efficient transportation schedules. A sensitivity analysis is conducted to determine the impact of changes in the transaction cost in favour of the co-procurement.     

A coordinated two-phase approach for operational decisions with vehicle routing in a single-vendor multi-buyer system

This study considers a two-echelon system in which a vendor produces a product at a finite production rate and supplies it to several buyers facing independent normally-distributed demands. The product is delivered to the buyers using a set of different speed vehicles with identical capacity and different operating costs. The issues of lead time reduction and the service level constraint on the buyers have been incorporated in the model. A model is formulated to determine the optimal production–inventory policy, vehicle routes and vehicle type for each route by minimising the related production, inventory, lead time crashing and transportation costs of the system while satisfying the service level constraint on each buyer. A coordinated two-phase iterative approach is proposed to solve the model. Finally, a numerical example is included to describe the solution approach and illustrate the results.     

Buyer behaviours and the performance of the supply chain: An international exploration

This paper studies the effects of buyer?supplier interaction in a supply chain environment. It focuses on the effects of buyer behaviours (such as supplier selection, number of suppliers, percentage of outsourcing, and frequency of production changes) on the performance of the supply chain. Using data collected from machine tool manufacturers around the world, the various behaviours of buyers are examined to see how they induce or mitigate the degree of uncertainty experienced by suppliers and thus affect suppliers' delivery performance. In addition, it was investigated how such buyer behaviours could further affect the supply chain's ability to perform as expected. The statistical results suggest that many buyer behaviours that have no direct effect on buyer's performance can have a significant effect on their suppliers' performance. Specifically, buyer behaviours directly manifest in supplier performance and only indirectly manifest in their own performance. This can give the buyer the false impression that the supply base is harming performance, when the real problem is the way the buyer manages the supply chain. The results vary by region of the world, suggesting that any theory that links buyer behaviours to supplier performance will need to consider a firm location.     

Two-phase selection framework that considers production costs of suppliers and quality requirements of buyers

Buyers are faced with selecting the optimal supplier, while suppliers are left to consider production costs. In this study, we developed a two-phase selection framework that allows buyers to evaluate the performance of suppliers while taking production costs into account for value maximisation. This scheme is a win-win solution capable of promoting long-term relationships between buyers and suppliers. Under the assumption of normality, the first phase involves constructing a new Six Sigma quality capability analysis chart (SSQCAC) which takes production costs into account. The objective is to evaluate all potential suppliers using the 100?×?(1–α)% upper confidence limit (UCL) of an integrated Six Sigma quality index (SSQI) Q_PIh when dealing with products with smaller-the-better (STB), larger-the-better (LTB), or nominal-the-best (NTB) quality characteristics. According to interval estimation theory, this method can have a significant impact on the consumption of resources; i.e. the production costs of the supplier can be decreased by reducing the production quality to below that required by the buyer. The proposed method also filters out unsuitable suppliers in order to simplify the decision problem and reduce computational demands and operational risks/costs without compromising the quality of the final product. In the second phase, a detailed analysis is conducted using Euclidean distance measure to select the optimal supplier from among the remaining candidates. We conducted a real-world case study to evaluate the efficacy of the proposed method. We also conducted comparisons with existing methods to demonstrate the advantages of the proposed method and its managerial implications. Suggestions for future study are also provided.     

EIAS: An Efficient Identity-Based Aggregate Signature Scheme for WSNs Against Coalition Attack

Wireless sensor networks (WSNs) are the major contributors to big data acquisition. The authenticity and integrity of the data are two most important basic requirements for various services based on big data. Data aggregation is a promising method to decrease operation cost for resource-constrained WSNs. However, the process of data acquisitions in WSNs are in open environments, data aggregation is vulnerable to more special security attacks with hiding feature and subjective fraudulence, such as coalition attack. Aimed to provide data authenticity and integrity protection for WSNs, an efficient and secure identity-based aggregate signature scheme (EIAS) is proposed in this paper. Rigorous security proof shows that our proposed scheme can be secure against all kinds of attacks. The performance comparisons shows EIAS has clear advantages in term of computation cost and communication cost when compared with similar data aggregation scheme for WSNs.     

Rewards-supply planning under option contracts in managing coalition loyalty programmes

We examine the problem of planning the supply of rewards in coalition loyalty programmes considering that the buyer–supplier relationships with commercial partners are governed by option contracts rather than wholesale price contracts similar to what is commonly used in practice. We develop a two-stage stochastic linear programme model with simple recourse which considers uncertain demand requirements, limited reward purchasing budgets, multiple programme partners of various sizes, point-liability control targets and overall profitability. A sampling average approximation scheme is used to solve the model. Numerical experiments show that option contracts perform better than wholesale price contracts when redemption demand uncertainty is high and the number of redemption partners is large. The results also suggest that the common practice of increasing redemption capacities is not the most effective way to cope with demand uncertainties. Programmes that reduce redemption demand variability and/or create better contracting structures are more promising in improving points-liability, redemption budget spending and overall profitability than traditional approaches.     

代理多重签名方案的密码分析与修改

对伊丽江等提出的的代理多重签名方案进行了详细的分析，指出该方案是不安全的，不能抵抗公钥替换攻击和合谋攻击，并给出了两个改进的代理多重签名方案。改进后的方案具有不可否认性，不使用安全信道，以及抵抗公钥替换攻击和合谋攻击等优点。     

Organisational resilience and relational dynamics in triadic networks: a multiple case analysis

This study aims to analyse resilience and relational dynamics (competitive, cooperative and co-opetitive) within a triadic buyer–supplier–supplier context. Our central goal is to show how a buyer’s supplier–supplier relational behaviour leads to and shapes resilience of this triad. We utilised a multiple-design case approach and selected eight buyers and their suppliers from the textile industry in Turkey. By analysing a triadic context from another industry, we conducted validation analyses. Our findings showed a pattern of relationship between the resilience and the relational dynamics of a triad. Built on theory and insights from the cases, we proposed three propositions. We argued that when co-opetition prevails in a triadic context of relations, the triad resilience level is highest. In competitive relational settings the triad resilience level is lowest, and when the relational dynamics are cooperative, the triad resilience level is moderate. This study is the first to introduce and discuss organisational resilience at triadic level. Furthermore, to our knowledge, our insights from cases are among the first attempts to link three types of supplier–supplier relational dynamics to triad resilience via the use of a multiple-design case approach. Therefore, our contributions are likely to extend the organisational resilience and buyer–supplier–supplier relations research.     

An energy‐momentum‐conserving temporal discretization scheme for adhesive contact problems

Numerical solution of dynamic problems requires accurate temporal discretization schemes. So far, to the best of the authors’ knowledge, none have been proposed for adhesive contact problems. In this work, an energy‐momentum‐conserving temporal discretization scheme for adhesive contact problems is proposed. A contact criterion is also proposed to distinguish between adhesion‐dominated and impact‐dominated contact behaviors. An adhesion formulation is considered, which is suitable to describe a large class of interaction mechanisms including van der Waals adhesion and cohesive zone modeling. The current formulation is frictionless, and no dissipation is considered. Performance of the proposed scheme is compared with other schemes. The proposed scheme involves very little extra computational overhead. It is shown that the proposed new temporal discretization scheme leads to major accuracy gains both for single‐degree‐of‐freedom and multi‐degree‐of‐freedom systems. The single‐degree‐of‐freedom system is critically analyzed for various parameters affecting the response. For the multi‐degree‐of‐freedom system, the effect of the time step and mesh discretization on the solution is also studied using the proposed scheme. It is further shown that a temporal discretization scheme based on the principle of energy conservation is not sufficient to obtain a convergent solution. Results with higher order contact finite elements for discretizing the contact area are also discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Absorptive and desorptive capacity configurations in supply chains: An inverted U-shaped relationship

The extant literature has highlighted the importance of knowledge transfer between a buyer and its supply network for strengthening supply chain competence. This is a bi-directional exchange where the buyer and supply network each act as the sender and receiver of knowledge. Prior research has however largely focused on the knowledge recipient only. We consider both sender and recipient using two key dynamic capabilities related to knowledge transfer: (i) desorptive capacity, which enables the safe transfer of knowledge from the sender; and, (ii) absorptive capacity, which enables the acquisition and assimilation of external knowledge by the recipient. Using the concept of ‘fit’, we investigate whether organisations strengthen supply chain competence when their desorptive capacity exceeds that of their supply network's (positive misfit) and consider the moderating role of the organisation’s and supply network’s absorptive capacity. Multiple regression analysis of survey data from 250 firms identifies an inverted U-shaped relationship between positive desorptive capacity misfit and supply chain competence. Further, this relationship is shown to be moderated by the supply network’s absorptive capacity level. The paper furthers our understanding of supply chain knowledge management enabling buyers and their supply networks to achieve more successful knowledge transfer outcomes.