Sequential and dynamic frameproof codes

There are many schemes in the literature for protecting digital data from piracy by the use of digital fingerprinting, such as frameproof codes and traitor-tracing schemes. The concept of traitor-tracing has been applied to a digital broadcast setting in the form of dynamic traitor-tracing schemes and sequential traitor-tracing schemes, which could be used to combat piracy of pay-TV broadcasts, for example. In this paper, we extend the properties of frameproof codes to this dynamic model, defining and constructing both l-sequential c-frameproof codes and l-dynamic c-frameproof codes. We also give bounds on the number of users supported by such schemes.      

Recursive constructions of secure codes and hash families using difference function families

To protect copyrighted digital data against piracy, codes with different secure properties such as frameproof codes, secure frameproof codes, codes with identifiable parent property (IPP codes), traceability codes (TA codes) are introduced. In this paper, we study these codes together with related combinatorial objects called separating and perfect hash families. We introduce for the first time the notion of difference function families and use these difference function families to give generalized recursive techniques that can be used for any kind of secure codes and hash families. We show that some previous recursive techniques are special cases of these new techniques.     

Constructions of almost secure frameproof codes with applications to fingerprinting schemes

This paper presents explicit constructions of fingerprinting codes. The proposed constructions use a class of codes called almost secure frameproof codes. An almost secure frameproof code is a relaxed version of a secure frameproof code, which in turn is the same as a separating code. This relaxed version is the object of our interest because it gives rise to fingerprinting codes of higher rate than fingerprinting codes derived from separating codes. The construction of almost secure frameproof codes discussed here is based on weakly biased arrays, a class of combinatorial objects tightly related to weakly dependent random variables.     

A bound on the size of separating hash families

The paper provides an upper bound on the size of a (generalized) separating hash family, a notion introduced by Stinson, Wei and Chen. The upper bound generalizes and unifies several previously known bounds which apply in special cases, namely bounds on perfect hash families, frameproof codes, secure frameproof codes and separating hash families of small type.     

A tight bound for frameproof codes viewed in terms of separating hash families

Frameproof codes have been introduced for use in digital fingerprinting that prevent a coalition of \(w\) or fewer legitimate users from constructing a fingerprint of another user not in the coalition. It turns out that \(w\) -frameproof codes are equivalent to separating hash families of type \(\{1,w\}\) . In this paper we prove a tight bound for frameproof codes in terms of separating hash families.     

New constructions for perfect hash families and related structures using combinatorial designs and codes

In this paper, we consider explicit constructions of perfect hash families using combinatorial methods. We provide several direct constructions from combinatorial structures related to orthogonal arrays. We also simplify and generalize a recursive construction due to Atici, Magliversas, Stinson and Wei [3]. Using similar methods, we also obtain efficient constructions for separating hash families which result in improved existence results for structures such as separating systems, key distribution patterns, group testing algorithms, cover‐free families and secure frameproof codes. © 2000 John Wiley & Sons, Inc. J Combin Designs 8:189–200, 2000     

Efficient Rabin-type Digital Signature Scheme

Rabin's cryptosystem was proved to be as hard as factorization. However, Rabin's digital signature schemes is probabilistic. This paper shows two efficient Rabin type digital signature schemes, a basic scheme and an improved scheme. Both schemes run much faster than Rabin's scheme. They are deterministic and the size of a signature is much smaller than that of a signature in Rabin's scheme. Furthermore, it is proved that, by applying the technique of Bellare and Rogaway, the proposed scheme is secure against chosen plaintext attack. More precisely, breaking the proposed digital signature scheme by chosen plaintext attack is as hard as factoring N.     

Empirical analysis of evolutionary algorithms with immigrants schemes for dynamic optimization

In recent years, there has been a growing interest in studying evolutionary algorithms (EAs) for dynamic optimization problems (DOPs). Among approaches developed for EAs to deal with DOPs, immigrants schemes have been proven to be beneficial. Immigrants schemes for EAs on DOPs aim at maintaining the diversity of the population throughout the run via introducing new individuals into the current population. In this paper, we carefully examine the mechanism of generating immigrants, which is the most important issue among immigrants schemes for EAs in dynamic environments. We divide existing immigrants schemes into two types, namely the direct immigrants scheme and the indirect immigrants scheme, according to the way in which immigrants are generated. Then experiments are conducted to understand the difference in the behaviors of different types of immigrants schemes and to compare their performance in dynamic environments. Furthermore, a new immigrants scheme is proposed to combine the merits of two types of immigrants schemes. The experimental results show that the interactions between the two types of schemes reveal positive effect in improving the performance of EAs in dynamic environments.     

A cryptographic watermarking technique for multimedia signals

Digital watermarking has been widely used in digital rights management and copyright protection. In this paper, new cryptographic watermark schemes are proposed. Compare to the existing watermarking techniques, our proposed watermark schemes combine both security and efficiency that none of the existing schemes can do. We first develop an algorithm to randomly generate the watermark indices based on the discrete logarithm problem (DLP) and the Fermat’s little theorem. Then we embed watermark signal into the host image in both time domain and frequency domain at the indices. Our security analysis and simulation demonstrate that our proposed schemes can achieve excellent transparency and robustness under the major security attacks and common signal degradations. The novel approaches provided in this paper are ideal for general purpose commercial digital media copyright protection.     

Numerical solving dynamic problems of elastoplastic deformation of solids

Numerical schemes for solving two-dimensional dynamic problems of elasticity theory based upon several local approximations for each of the required functions are discussed. The schemes contain free parameters (dissipation constants). An explicit form of artificial dissipation of the solutions allows us to control its size and to effectively construct both explicit and implicit schemes. The principle of producing such schemes is applied to a plane dynamic problem of elasticity theory as an example. We describe a class of problems for which numerical algorithms using several local approximations for each of the required functions are constructed. Examples of solving practical problems are given.     

Partial-match retrieval for dynamic files

This paper studies file designs for answering partial-match queries for dynamic files. A partial-match query is a specification of the value of zero or more fields in a record. An answer to a query consists of a listing of all records in the file satisfying the values specified.The main contribution is a general method whereby certain primary key hasing schemes can be extended to partial-match retrieval schemes. These partial-match retrieval designs can handle arbitrarily dynamic files and can be optimized with respect to the number of page faults required to answer a query.We illustrate the method by considering in detail the extension of two recent dynamic primary key hashing schemes.     

Security of meta-He digital signature scheme based on factoring and discrete logarithms

To enhance the security of signature schemes, Pon et al., recently, investigated all eight variants of the He’s digital signature scheme. The security of the proposed schemes is based on the difficulties of simultaneously solving the factoring and discrete logarithm problems with almost the same sizes of arithmetic modulus. This paper shows that the all eight variants of the He’s digital signature scheme, as well as two more variants, are not secure if attackers can solve discrete logarithm problems. Moreover, the attackers can easily forge signatures of the most optimal signature schemes of the generalized He’ signature schemes even though they can solve neither discrete logarithm problems nor factoring.     

Adjoint-coordinated approximations and economical discrete implementations in a dynamic problem of the linear theory of elasticity

For dynamic three-dimensional problems of the elasticity theory, we construct a new class of economical implicit difference schemes with high degree of parallelism. They include difference schemes whose parallelism degree is the same as for ordinary explicit schemes. So far, even the very existence of implicit schemes with the same parallelism degree has been strongly doubted.     

The impact of digital channel distribution on the experience goods industry

We explore the impact of a digital channel for experience goods on the profitability and behavior of players in the supply chain and on piracy. We consider a firm which can sell an experience good in physical form, in digitized form, or both. We analyze different pricing schemes – price for whole album on the retail channel and linear and nonlinear pricing for songs on the digital channel. Consumers are divided into a retail-captive segment whose consumers are limited to the retail channel and a hybrid segment whose consumers have access to both retail and digital channels.     

平台动态激励、消费采纳与数字内容创新——基于三方主体演化博弈分析

为探索多元参与主体对数字内容创新过程的影响机制,本研究对数字内容创新活动利益相关者进行界定并分析其行为逻辑与影响因素,通过构建数字内容平台方、数字内容提供方和数字内容消费方三方演化博弈模型,运用复制动态方程分析以及Matlab软件仿真分析,模拟三方博弈主体在数字内容创新中的策略演化路径。研究结果表明,数字内容创新机制是在数字内容平台方主导创新激励、数字内容提供方选择性创新,数字消费方采纳支持创新的三方动态博弈中不断协同演进的过程,数字内容平台方对数字内容消费方创新采纳行为决策的补偿力度与数字内容提供方收益分成比例两大因素对数字内容创新有决定性影响。其研究结论为完善平台经济视角下的数字内容创新机制提供了相关对策建议。     

On the determination of natural frequencies and mode shapes of cable-stayed bridges

An accurate analysis of the natural frequencies and mode shapes of a cable-stayed bridge is fundamental to the solution of its dynamic responses due to seismic, wind and traffic loads. In most previous studies, the stay cables have been modelled as single truss elements in conventional finite element analysis. This method is simple but it is inadequate for the accurate dynamic analysis of a cable-stayed bridge because it essentially precludes the transverse cable vibrations. This paper presents a comprehensive study of various modelling schemes for the dynamic analysis of cable-stayed bridges. The modelling schemes studied include the finite element method and the dynamic stiffness method. Both the mesh options of modelling each stay cable as a single truss element with an equivalent modulus and modelling each stay cable by a number of cable elements with the original modulus are studied. Their capability to account for transverse cable vibrations in the overall dynamic analysis as well as their accuracy and efficiency are investigated.     

Completely conservative difference schemes for dynamic problems of linear elasticity and viscoelasticity

On the basis of a mixed statement (velocity-strain), we complete the development of a general theory of completely conservative adjoint-coordinated difference schemes for dynamic problems of linear elasticity and viscoelasticity. In particular, our explicitly solvable discrete models permit controlling the total energy imbalance and have the same parallelization degree as the conventional explicit schemes.     

Classification of three-class association schemes using backtracking with dynamic variable ordering

We describe several techniques for the exhaustive computer generation of non-isomorphic association schemes with a given set of intersection numbers using a backtracking algorithm with forward checking and dynamic variable ordering. We have applied these techniques to the classification of certain open parameter sets for three-class association schemes listed by Van Dam in (Three-class association schemes, J. Algebraic Combin. 10 (1999) 69–107) for which we present several new results. Among these are some new (imprimitive) distance regular graphs of diameter 3.     

流体力学方程组的总熵增量小的守恒型差分格式(续)

近年来,国外许多学者对求解双曲守恒律组的高分辨率、高精度差分格式进行了深入的研究.例如MUSCL方法、TVD格式、PPM方法、各种限流的方法以及ENO格式等等.将这些方法应用于流体力学方程组,其数值实践的结果表明,在消除波后振荡、提高激波间断分辨率、提高计算精度等方面有明显的效果.在设计这些计算格式时,通常都是研究单个标量方程的计算格式,再推广到方程组的情形.同时,或者对数值解的总变差提出某种要求(不增或基本不增),或者采用修正数值流措施,或者采用插值或重构的方法,在网格内部用线性分布和更高阶的分布取代Godunov方法中的常数分布,以及处理相应的小范围的解的算法.     

Discrete-Time Linear-Quadratic Dynamic Games

Finite-dimensional, time invariant, linear quadratic dynamic games are perhaps the best understood and researched class of dynamic games. This is particularly true for continuous-time linear quadratic differential games. In this paper, the application of the theory of dynamic games to signal processing is considered. We are interested in digital signal processing and therefore we confine our attention to discrete-time linear-quadratic dynamic games (LQDG). In discrete-time the cost function contains product terms between the decision variables which complicates the analysis compared to its continuous-time analogue. With a view to facilitate the application of the theory of dynamic games to digital signal processing, and in particular, disturbance rejection, the complete solution of the discrete-time LQDG is worked out and explicit results are obtained. Thus,discrete-time LQDGs have the distinct advantage of being amenable to analysis, closed-form solutions are possible, and one is in tune with modern digital signal processing techniques. In this paper, minimal necessary and sufficient conditions for the existence of a solution to the discrete-time LQDG are provided and its explicit, closed-form, solution is worked out. This opens the way to designing novel digital signal processing algorithms for disturbance rejection. Information plays a critical role in game theory and in particular in dynamic games. Using our explicit solution of the deterministic LQDG, a hierarchy of three zero-sum stochastic LQDGs characterized by a sequence of information patterns which increase in complexity is analyzed.