controlling access in tree hierarchies abstract inspired from sandhu s scheme this paper presents a cryptographic key assignment scheme in tree hierarchies for access control initially the root security class is assigned an arbitrary secret key which is a 3 dimensional row vector any other security class s secret key can be generated or derived from its ancestor s secret key as needed in our scheme the secret key can be used directly as an encryption key or used as an encryption encryption key for generating an encryption key to encipher the owned information items our scheme preserves the advantages of sandhu s scheme such as a new security class can be defined easily and the size of secret key is fixed furthermore each security class can freely choose or change its encryption key for protecting the owned information items without altering the existing secret keys

a labeling algorithm for the fuzzy assignment problem abstract this paper concentrates on the assignment problem where costs are not deterministic numbers but imprecise ones here the elements of the cost matrix of the assignment problem are subnormal fuzzy intervals with increasing linear membership functions whereas the membership function of the total cost is a fuzzy interval with decreasing linear membership function by the max min criterion suggested by bellman and zadeh the fuzzy assignment problem can be treated as a mixed integer nonlinear programming problem we show that this problem can usually be simplified into either a linear fractional programming problem or a bottleneck assignment problem here we propose an efficient algorithm based on the labeling method for solving the linear fractional programming case the algorithm begins with primal feasibility and proceeds to obtain dual feasibility while maintaining complementary slackness until the primal optimal solution is found the computational results show that the proposed labeling algorithm offers an effective and efficient way for handling the fuzzy assignment problem

a new possibilistic programming approach for solving fuzzy multiobjective assignment problem in this paper we propose a new possibilistic programming approach to solve a fuzzy multiobjective assignment problem in which the objective function coefficients are characterized by triangular possibility distributions the proposed solution approach simultaneously minimizes the best scenario the likeliest scenario and the worst scenario for the imprecise objective functions using level sets the level sets are used to define the confidence level of the fuzzy judgments of the decision maker additionally we provide a systematic framework in which the decision maker controls the search direction by updating both the membership values and aspiration levels until a set of satisfactory solutions is obtained numerical examples with dataset from realistic situations are provided to demonstrate the effectiveness of the proposed approach

treatment of combinatorial optimization problems using selection equations with cost terms part ii np hard three dimensional assignment problems abstract this paper is the first of two parts part ii physica d 134 1999 242 252 which present a novel approach to the solution of assignment problems using time continuous dynamical systems this first part concentrates on the two dimensional assignment problem of combinatorial optimization while in the second part the np hard three dimensional problem is treated the proposed dynamical system approach works by using coupled selection equations with cost terms this is a combination of two basic ideas namely first coupled selection processes with suitably chosen initial values where the dynamical system has suitable asymptotically stable points which represent the feasible solutions of the assignment problem it is an important fact that there are feasible solutions only and no spurious states in this system the second idea is based on the appropriate distortion of the basins of attraction of the asymptotically stable points by cost terms similar to classical penalty methods

a novel key management scheme for dynamic access control in a user hierarchy considering the solution of dynamic access problems in a user hierarchy a novel scheme based on one way hash function is proposed to manage the cryptographic keys in the paper the scheme attempts to achieve both efficiency and non iteration in deriving the successor s secret key besides the other issues in relation with dynamic access control problems such as adding deleting classes adding deleting relationships and changing secret keys can be held good to the scheme in view of security a competent central authority must provide the user a convenient way to change his her key at any time therefore the design toward the algorithm in the paper contains such a function what weight to mention especially among these characteristics of the scheme is the simplification of procedure in changing the private key and no other current keys need altering simultaneously

interactive multiple objective programming subject to flexible constraints abstract an interactive decision support system is introduced which aids in solving multiple objective programming problems subject to strict and flexible constraints integral part is an extension of a well known fuzzy sets approach evaluating possible solutions by their degrees of membership to objectives and constraints this approach is linked to classical multiple objective programming models if the decision maker cannot determine membership functions a priori the system suggests functions dependent on the given information and interactive modifications are allowed

ranking function based solutions of fully fuzzified minimal cost flow problem the aim of minimal cost flow problem mcfp is to find the least transportation cost of a single commodity through a capacitated network this paper presents a model to deal with one particular group of such problems in which the supply and demand of nodes and the capacity and cost of edges are represented as fuzzy numbers for easier reference hereafter we refer to this group of problems as fully fuzzified mcfp to represent our model hukuhara s difference and approximated multiplication are used thereafter we sort fuzzy numbers by an order using a ranking function and show that it is a total order i e a reflexive anti symmetric transitive and complete binary relation utilizing the proposed ranking function we transform the fully fuzzified mcfp into three crisp problems solvable in polynomial time from this standpoint combinatorial algorithms are provided to solve the above mentioned problem and find the fuzzy optimal flow furthermore the proposed order is related to the importance weights of the center the left spread and the right spread of each fuzzy number thus this method is capable of handling the decision maker s risk taking by comparing some previous ranking function based works with our method the efficiency of the latter is revealed finally an application of our proposed method to petroleum industry is presented

access control in user hierarchy based on elliptic curve cryptosystem this work proposes a novel key management method based on elliptic curve cryptosystem and one way hash function to solve dynamic access problems in a user hierarchy the proposed scheme attempts to derive the secret key of successors efficiently and non redundantly it includes functions such as insertion and removal of classes updating of their relationships and changing of secret keys the method utilizes a central authority which enables a user to change the secret key at will conveniently since the proposed method uses the elliptic curve cryptosystem which has a low computational cost and small key size its performance in terms of both security and efficiency is quite commendable therefore it can be anticipated that its use will be extended to wireless communication in the future

general forms for maximal ratio diversity with weighting errors this paper introduces two general relationships concerning the output signal to noise ratio distribution and the bit error performance of the nonideal maximal ratio combiner the imperfections are modeled as gaussian distributed weighting errors in the channel gain estimates used for coherent combination the general form for the bit error rate is applicable to any modulation format

a dynamic cryptographic key assignment scheme in a tree structure abstract in this paper we propose a dynamic cryptographic key assignment scheme based on newton s interpolation method and a predefined one way function all users are classified into disjoint sets of security classes that employ the relation of partial ordering that is a security class at higher level can derive from his own cryptographic key the keys of the other security class below him compared with the existing assignment schemes our scheme always produces economic cryptographic keys which are smaller than the keys generated by the previous work in a tree structure furthermore whenever a new security class is inserted into the user hierarchy system the corresponding keys can be determined without changing any existing keys therefore our scheme is suitable for practical implementation

the fuzzy quadratic assignment problem with penalty new models and genetic algorithm the assignment problem is to find the total costs optimal jobs assignment schedule where n jobs are allocated to n workers and each worker receives exactly just one job such that the total cost is optimal the quadratic assignment problem with penalty takes three types of costs into consideration direct cost interactive cost an penalty in this paper the fuzzy quadratic assignment problem with penalty is formulated as expected value model chance constrained programming and dependent chance programming according to various decision criteria and the crisp equivalents are given furthermore hybrid genetic algorithm is designed for solving the proposed fuzzy programming models

an efficient key assignment scheme for access control in a large leaf class hierarchy the employees of an organization are usually divided into different security classes to authorize the information retrieval and the number of leaf classes is substantially larger than the number of non leaf classes additionally the alternations in leaf classes are more frequent than in non leaf classes we proposed a new key assignment scheme for controlling the access right in a large poset partially ordered set hierarchy to reduce the required computation for key generation and derivation with the storage amount of data decreased

an integer fuzzy transportation problem abstract the well known transportation problem 1 is often represented by a bipartite network that consists of two node sets i e sets of supply or plant and demand or warehouse nodes the problem is to determine a flow such that the total transportation cost is minimized however in some situations the values of supplies and demands may not be determined rigidly accordingly we considered a fuzzy version of the transportation problem by introducing two kinds of membership functions which characterize fuzzy supplies and fuzzy demands 2 the objective is to determine an optimal flow that maximizes the smallest value of all membership functions under the constraint that the total transportation cost must not exceed a certain upper limit in this paper we generalize the fuzzy transportation problem that is an integral constraint of flow is added to the problem we call it iftp integer fuzzy transportation problem in which it is assumed that every value of supply and demand is integer and that the values of commodities to be transported are all integers

a fuzzy shortest path with the highest reliability this paper concentrates on a shortest path problem on a network where arc lengths costs are not deterministic numbers but imprecise ones here costs of the shortest path problem are fuzzy intervals with increasing membership functions whereas the membership function of the total cost of the shortest path is a fuzzy interval with a decreasing linear membership function by the max min criterion suggested in r e bellman l a zade decision making in a fuzzy environment management science 17b 1970 141 164 the fuzzy shortest path problem can be treated as a mixed integer nonlinear programming problem we show that this problem can be simplified into a bi level programming problem that is very solvable here we propose an efficient algorithm based on the parametric shortest path problem for solving the bi level programming problem an illustrative example is given to demonstrate our proposed algorithm

a fuzzy transportation algorithm this paper proposes an algorithm for solving transportation problems with fuzzy constraints and investigates the relationship between the algebraic structure of the optimum solution of the deterministic problem and its fuzzy equivalent

a new possibilistic optimization model for multiple criteria assignment problem this paper presents a new multiple criteria optimization model of an assignment problem with imprecise coefficients besides minimizing the total cost total time of finishing jobs and maximization of the overall achieved quality we introduce a new criterion that minimizes the number of workers employed to finish all jobs it contributes significantly in multi job assignment to adjust the number of workers assigned to at least one job for balancing work allocation among the workers furthermore we employ new diversification constraints to obtain a reasonable tradeoff between the number of workers employed and number of jobs assigned a new interactive possibilistic programming approach is developed for trapezoidal possibility distributions which uses alpha level sets to incorporate confidence levels of the decision maker in his fuzzy judgments leading to alpha efficient solutions numerical experiments are conducted using data coming from a manpower planning problem to demonstrate working of the proposed multiple criteria assignment model and effectiveness of the fuzzy interactive approach

fuzzy integer transportation problem an algorithm has been proposed which solves the transportation problem with fuzzy supply and demand values and the integrality condition imposed on the solution this algorithm is exact and computationally effective although the problem is formulated in the general way i e its fuzzy supply and demand values can differ from each other and be fuzzy numbers of any type

an efficient hierarchy scheme for determining relationships in information systems abstract in this paper a dynamic user hierarchy mechanism based on key pairs is proposed through careful design of keys we get an economic integer key pair for each user in our scheme the relationship between two users can be easily revealed by performing a simple formula to the key pair furthermore by applying our scheme whenever a new user is inserted into the user hierarchy system the corresponding key pair can be determined quickly without changing any existing key pairs

computing improved optimal solutions to max min flexible constraint satisfaction problems abstract the formal framework for decision making in a fuzzy environment is based on a general max min bottleneck like optimization problem proposed by zadeh it is also the basis for extending the constraint satisfaction paradigm of artificial intelligence to accommodating flexible or prioritized constraints this paper surveys refinements of the ordering of solutions supplied by the max min formulation namely the discrimin partial ordering and the leximin complete preordering a general algorithm is given which computes all maximal solutions in the sense of these relations it also sheds light on the structure of the set of best solutions moreover classes of problems for which there is a unique best discrimin and leximin solution are exhibited namely continuous problems with convex domains and so called isotonic problems noticeable examples of such problems are fuzzy linear programming problems and fuzzy pert like scheduling problems

a fuzzy approach to the transportation problem abstract the transportation problem with fuzzy supply values of the deliverers and with fuzzy demand values of the receivers is analysed for the solution of the problem the technique of parametric programming is used this makes it possible to obtain not only the maximizing solution according to the bellman zadeh criterion but also other alternatives close to the optimal solution

asymptotic performance of m ary orthogonal signals in worst case partial band interference and rayleigh fading it is shown that for worst case partial band jamming the error probability performance for fixed e sub b n sub i becomes worse with increasing m for m 16 the asymptotic probability of error is not zero for any e sub b n sub i ln 2 but decreases inverse linearly with respect to it in the fading case the error probability performance for fixed e sub b n sub 0 improves with m for noncoherent detection but worsens with m for coherent detection for large e sub b n sub 0 the performance of the rayleigh fading channel asymptotically approaches the same limit as the worst case partial band jammed channel however for values of m at least up to 4096 the partial band jammed channel does better while it is unlikely that an m ary orthogonal signal set with m 1024 will be used in a practical situation these results suggest an important theoretical problem namely what signal set achieves reliable communication

set valued cooperative games with fuzzy payoffs the fuzzy assignment game abstract in this paper we study cooperative games with fuzzy payoffs the main advantage of the approach presented is the incorporation into the analysis of the problem of ambiguity inherent in many real world collective decision situations we propose extensions of core concepts which maintain the fuzzy nature of allocations and lead to a more satisfactory study of the problem within the fuzzy context finally we illustrate the extended core concepts and the approach to obtain the corresponding allocations through the analysis of assignment games with uncertain profits

an optimal algorithm for assigning cryptographic keys to control access in a hierarchy a cryptographic scheme for controlling access to information within a group of users organized in a hierarchy was proposed in 1 the scheme enables a user at some level to compute from his own cryptographic key the keys of the users below him in the organization

the design of an arithmetic coding mechanism to determine relationships in a hierarchy abstract in this paper a dynamic user hierarchy mechanism based on arithmetic coding is proposed through careful design of keys some economic keys are obtained in our scheme the relationship between two users can be easily revealed by evaluating a simple formula to the relative key in addition whenever a new user is inserted into the user hierarchy system the corresponding keys can be determined quickly without changing the existing keys except for the last existing key furthermore the keys proposed by us are drastically reduced from the previous work

interactive fuzzy programming for two level linear and linear fractional production and assignment problems a case study abstract in this paper we deal with actual problems on production and work force assignment in a housing material manufacturer and a subcontract firm we formulate two kinds of two level programming problems one is a profit maximization problem of both the housing material manufacturer and the subcontract firm and the other is a profitability maximization problem of them applying the interactive fuzzy programming for two level linear and linear fractional programming problems we derive satisfactory solutions to the problems after comparing the two problems we discuss the results of the applications and examine actual planning of the production and the work force assignment of the two firms to be implemented

a two objective fuzzy k cardinality assignment problem this paper investigates a two objective k cardinality assignment problem as a result a chance constrained goal programming model is constructed for the problem also tabu search algorithm based on fuzzy simulation is designed to solve the problem finally a numerical example is presented to show the application of the algorithm

hidden attribute based signatures without anonymity revocation we propose a new notion called hidden attribute based signature which is inspired by the recent developments in attribute based cryptosystem with this technique users are able to sign messages with any subset of their attributes issued from an attribute center in this notion a signature attests not to the identity of the individual who endorsed a message but instead to a claim regarding the attributes the underlying signer possesses users cannot forge signature with attributes which they have not been issued furthermore signer remains anonymous without the fear of revocation among all users with the attributes purported in the signature after formalizing the security model we propose two constructions of hidden attribute based signature from pairings the first construction supports a large universe of attributes and its security proof relies on the random oracle assumption which can be removed in the second construction both constructions have proven to be secure under the standard computational diffie hellman assumption

the solution and duality of imprecise network problems duality properties have been investigated by many researchers in the recent literature they are introduced in this paper for a fully fuzzified version of the minimal cost flow problem which is a basic model in network flow theory this model illustrates the least cost of the shipment of a commodity through a capacitated network in terms of the imprecisely known available supplies at certain nodes which should be transmitted to fulfil uncertain demands at other nodes first we review on the most valuable results on fuzzy duality concepts to facilitate the discussion of this paper by applying hukuhara s difference approximated and exact multiplication and wu s scalar production we exhibit the flow in network models then we use combinatorial algorithms on a reduced problem which is derived from fully fuzzified mcfp to acquire fuzzy optimal flows to give duality theorems we utilize a total order on fuzzy numbers due to the level of risk and realize optimality conditions for providing some efficient combinatorial algorithms finally we compare our results with the previous worthwhile works to demonstrate the efficiency and power of our scheme and the reasonability of our solutions in actual decision making problems

performance analysis of linear modulation schemes with generalized diversity combining on rayleigh fading channels with noisy channel estimates generalized diversity combining gdc also known as hybrid selection maximal ratio combining or generalized selection combining is a low complexity diversity combining technique by which a fixed subset of a large number of available diversity channels is chosen and then combined using the rules of maximal ratio combining in this paper we analyze the performance of gdc on time correlated rayleigh fading channels with noisy channel estimates we derive expressions for the probability of error for various linear modulation schemes with coherent detection and discuss the conditions under which the analysis can be extended to noncoherent and differentially coherent receiver structures throughout the paper using a fundamental approach to obtain the decision statistic at the combiner output a number of new expressions for the error probabilities are obtained in a rigorous way along with a presentation of their performance with channel estimation errors the final expressions have roughly the same complexity of evaluation as that for the channel with only additive gaussian noise our results correct various inaccuracies in the literature and show that coherent receivers based on imperfectly estimated channel knowledge incur a significant performance loss

cryptanalysis and improvement of an access control in user hierarchy based on elliptic curve cryptosystem in a key management scheme for hierarchy based access control each security class having higher clearance can derive the cryptographic secret keys of its other security classes having lower clearances in 2008 chung et al proposed an efficient scheme on access control in user hierarchy based on elliptic curve cryptosystem information sciences 178 1 2008 230 243 their scheme provides solution of key management efficiently for dynamic access problems however in this paper we propose an attack on chung et al s scheme to show that chung et al s scheme is insecure against the exterior root finding attack we show that under this attack an attacker adversary who is not a user in any security class in a user hierarchy attempts to derive the secret key of a security class by using the root finding algorithm in order to remedy this attack we further propose a simple improvement on chung et al s scheme overall the main theme of this paper is very simple a security flaw is presented on chung et al s scheme and then a fix is provided in order to remedy the security flaw found in chung et al s scheme

adaptive orthogonal signaling with diversity in a frequency nonselective rayleigh fading channel power and rate adaptations with diversity are considered for m ary orthogonal signals in a frequency nonselective rayleigh fading channel we derived the minimum required e sub b n sub 0 for a given probability of error the maximum average data rate and the outage probability when maximal ratio combining is performed with an imperfect channel estimation we analyzed the effects of channel estimation errors on the required e sub b n sub 0 and outage probability as a function of diversity order and adaptation methods the relative benefits of rate and power control techniques are further presented in terms of channel estimation error diversity order and outage probability the minimum required e sub b n sub 0 with reed solomon codes is also presented for comparison purposes

performance limits of reed solomon coded cdma with orthogonal signaling in a rayleigh fading channel the asymptotic performance of reed solomon rs coded m ary orthogonal signaling with ratio threshold test rtt type demodulation in a rayleigh fading channel is considered we show that the minimum e sub b n sub 0 needed for error free communication is eln2 2 75 db with rtt and 4 79 6 8 db with hard decisions the optimum code rate that minimizes the required e sub b n sub 0 is e sup 1 with rtt and 0 46 with hard decision and the optimum ratio threshold approaches 1 for large m next we investigate the fundamental limit in a direct sequence spread spectrum multiple access ds ssma system employing an m ary orthogonal code of length n mm which is obtained by spreading every row of an m spl times m hadamard matrix with a user specific random sequence of length n we derive the minimum e sub b n sub 0 for error free communication as a function of the number of users the optimum code rate that minimizes e sub b n sub 0 and the maximum limit on the total information transmission rate then we consider a multirate ds ssma system where a population of users simultaneously transmit at different power levels a variety of traffic types of different information rates we derive the minimum required e sub b n sub 0 and the optimum code rate for each traffic type

a secure effective key management scheme for dynamic access control in a large leaf class hierarchy lo et al 2011 proposed an efficient key assignment scheme for access control in a large leaf class hierarchy where the alternations in leaf classes are more frequent than in non leaf classes in the hierarchy their scheme is based on the public key cryptosystem and hash function where operations like modular exponentiations are very much costly compared to symmetric key encryptions and decryptions and hash computations their scheme performs better than the previously proposed schemes however in this paper we show that lo et al s scheme fails to preserve the forward security property where a security class c x can also derive the secret keys of its successor classes c j s even after deleting the security class c x from the hierarchy we aim to propose a new key management scheme for dynamic access control in a large leaf class hierarchy which makes use of symmetric key cryptosystem and one way hash function we show that our scheme requires significantly less storage and computational overheads as compared to lo et al s scheme and other related schemes through the informal and formal security analysis we further show that our scheme is secure against all possible attacks including the forward security in addition our scheme supports efficiently dynamic access control problems compared to lo et al s scheme and other related schemes thus higher security along with low storage and computational costs make our scheme more suitable for practical applications compared to other schemes

new constructions for provably secure time bound hierarchical key assignment schemes a time bound hierarchical key assignment scheme is a method to assign time dependent encryption keys to a set of classes in a partially ordered hierarchy in such a way that each class in the hierarchy can compute the keys of all classes lower down in the hierarchy according to temporal constraints in this paper we propose new constructions for time bound hierarchical key assignment schemes which are provably secure with respect to key indistinguishability our constructions use as a building block any provably secure hierarchical key assignment scheme without temporal constraints and exhibit a tradeoff among the amount of private information held by each class the amount of public data the complexity of key derivation and the computational assumption on which their security is based moreover the proposed schemes support updates to the access hierarchy with local changes to public information and without requiring any private information to be re distributed

a concept of the optimal solution of the transportation problem with fuzzy cost coefficients abstract in the paper a definition of the optimal solution of the transportation problem with fuzzy cost coefficients as well as an algorithm determining this solution are proposed

efficient provably secure hierarchical key assignment schemes a hierarchical key assignment scheme is a method to assign some private information and encryption keys to a set of classes in a partially ordered hierarchy in such a way that the private information of a higher class can be used to derive the keys of all classes lower down in the hierarchy in this paper we design and analyze hierarchical key assignment schemes which are provably secure and support dynamic updates to the hierarchy with local changes to the public information and without requiring any private information to be re distributed we first consider the problem of constructing a hierarchical key assignment scheme by using as a building block a symmetric encryption scheme we propose a new construction which is provably secure with respect to key indistinguishability requires a single computational assumption and improves on previous proposals then we show how to construct a hierarchical key assignment scheme by using as a building block a public key broadcast encryption scheme in particular one of our constructions provides constant private information and public information linear in the number of classes in the hierarchy