Scramble algorithms, which are also called pure-position permutation algorithms, are commonly used as an image encryption, are investigated in this paper. Unfortunately, they are frail under known-text attack. Accordi...
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Scramble algorithms, which are also called pure-position permutation algorithms, are commonly used as an image encryption, are investigated in this paper. Unfortunately, they are frail under known-text attack. According to the weakness of pure position permutation algorithm, we put forward an effective decryption algorithm for all pure-position permutation algorithms. First, a summary of the pure position permutation image encryption algorithms is given by introducing the concept of ergodic matrices. Secondly, by using probability theory and algebra knowledge, the decryption probability of pure-position permutation algorithms is verified theoretically. Then, by defining operation system of fuzzy ergodic matrices, we improve a specific decryption algorithm. Finally, some simulation results are shown.
Scheduling algorithms based on task duplication are of better performance than non-duplication ones. The paper analyzes typical scheduling algorithms based on task duplication (e.g. TDS, OSA algorithm) and their assum...
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Scheduling algorithms based on task duplication are of better performance than non-duplication ones. The paper analyzes typical scheduling algorithms based on task duplication (e.g. TDS, OSA algorithm) and their assumptions, then puts forward the algorithm of Processor Pre-Allocation (PPA) based on task duplication, whose primary aim is to get the shortest scheduling length, and secondary aim to utilize less number of processors, without any restricted conditions of task comp.ting time and communication time between tasks (namely task granularity is not taken into account). comp.red with correlative algorithms, PPA algorithm has advantages in scheduling length and the number of processors over others, but has the same time comp.exity. That is important for embedded real-time distributed systems.
Model checking is used mainly to check if a system satisfies the specifications expressed in temporal logic and people pay little attention to the model checking problem for logics of knowledge. However, in the distri...
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Model checking is used mainly to check if a system satisfies the specifications expressed in temporal logic and people pay little attention to the model checking problem for logics of knowledge. However, in the distributed systems community, the desirable specifications of systems and protocols are expressed widely in logics of knowledge. The model checking approaches for the temporal logic of knowledge are discussed. On the base of SMV (symbolic model verifier), according to the semantics of knowledge and set theory, several approaches for model checking of knowledge and common knowledge are presented. These approaches make SMV's functions extended from temporal logics to temporal logics of knowledge. They also correspond to other model checking approaches and tools where the output is the set of states.
Role-based Access Control (RABC) is an important information security model. In order to describe the information flow based on this model, a new security information flow model based on roles is given. The object is ...
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Role-based Access Control (RABC) is an important information security model. In order to describe the information flow based on this model, a new security information flow model based on roles is given. The object is expended, the basic principle of the RBAC model is used, the safe classify of the object is divided by its role set, and the information flow role is described with the included relation of the role set of two objects. By strict mathematical verification, this new information flow model satisfies the character of finite lattice and least upper bound operator, and it is reasonable and safe. Lastly one simple application is given.
As one stream standard which will be produced by the ITU-T and ISO in the future, Draft JVT (joint video team) is a new video-audio coding standard. Its goal is to produce a significant comp.ession performance relativ...
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As one stream standard which will be produced by the ITU-T and ISO in the future, Draft JVT (joint video team) is a new video-audio coding standard. Its goal is to produce a significant comp.ession performance relative to all the existing video coding standards in bit saving, procession quality and comp.ession efficiency by some measures which include slice technology, high resolution variable pixels, different block sizes and shapes, intra/inter prediction and coding from multiple reference pictures, etc. On the other hand, JVT would be designed to offer a transparent translation over different networks and increase network friendliness by information encapsulation and precedence control technologies. Although the basic coding framework of the standard is similar to that of currently popular video standards, JVT includes many new coding features which are presented in the paper. First, a broad view on video-audio coding standards is given. Second, the structure of JVT is presented. Then, both the detailed technologies which improve on coding efficiency of the VCL (video coding layer) and the key terms which are used in NAL (network abstraction layer) are introduced, which is the core in the paper. Finally, the current problems and the challenges of JVT's future research are discussed and analyzed.
To meet the increasing popularity of secure group-oriented comp.ting, this paper proposes an efficient group key agreement scheme-PAGKA. It combines the merit of key tree and Pairings-based key exchange, and involves ...
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To meet the increasing popularity of secure group-oriented comp.ting, this paper proposes an efficient group key agreement scheme-PAGKA. It combines the merit of key tree and Pairings-based key exchange, and involves members' long-term keys and session random in the group key to avoid dependence on signature or media access control (MAC). The PAGKA protocol suite is communication efficient, and has the following cryptographic properties such as key independence, implicit key authentication, perfect forward secrecy and resistance to known-key attacks and man-in-the-middle attacks. The idea in PAGKA can be used as a general method to extend authenticated two-party key agreement protocol to group settings.
This paper presents a distributed multi-agent planning algorithm based on constraints propagating. In our algorithm, conflicts are detected and resolved through a special type of negotiation among agents, i.e. consist...
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This paper presents a distributed multi-agent planning algorithm based on constraints propagating. In our algorithm, conflicts are detected and resolved through a special type of negotiation among agents, i.e. consistency checking for constraints. The algorithm is sound under deterministic circumstance. In our algorithm, agents only exchange information about actions, casual links and constraints related to conflicts. It is of less communication, higher security than that exchanging the whole plan.
A scheme called Freeze-TCP + is presented to improve the performance of transmission control protocol (TCP) in mobile environment. Freeze-TCP + is based on Freeze-TCP and incorporates network measurement mechanism. Da...
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A scheme called Freeze-TCP + is presented to improve the performance of transmission control protocol (TCP) in mobile environment. Freeze-TCP + is based on Freeze-TCP and incorporates network measurement mechanism. Data sender in Freeze-TCP + would not send all the packets in the window immediately as it does in Freeze-TCP when handover occurs but set its slow start threshold to a measurement result and start to transmit packets from slow start phase. Freeze-TCP + solve the problems that Freeze-TCP faces when handover occurs in heterogeneous networks, i.e., many packets are lost due to burst transmission or the resources in the new network can not be utilized efficiently. Network simulation shows that Freeze-TCP + can improve the performance of Freeze-TCP whatever kinds of handover occur.
The problem of an ogival nose rigid projectile penetrating into a thick target has been considered based on a semi-theoretical model in order to determine the velocity potential and the velocity field in the target. T...
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The problem of an ogival nose rigid projectile penetrating into a thick target has been considered based on a semi-theoretical model in order to determine the velocity potential and the velocity field in the target. The nose shape is simplified as a semi-Rankine ovoid similar to that of real long rod projectiles, and the details in nose shape does not significantly influence the penetration depth and the residual velocity in the case of thick targets. A code was comp.led based on the analysis of velocity and stress fields in targets, and used to calculate penetration and perforation of an ogival nose steel projectile into thick aluminum targets. A good agreement in residual velocity and penetration depth between the calculation and the experiments is achieved without any adjustment in material property parameters.
This paper developed a spherical cavity-expansion penetration model for concrete targets. The hydrostatic pressure-volumetric strain relation of concrete targets expressed by different solid concrete models and porous...
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This paper developed a spherical cavity-expansion penetration model for concrete targets. The hydrostatic pressure-volumetric strain relation of concrete targets expressed by different solid concrete models and porous model. Concrete has a tension cutoff value and its shear strength relevant to pressure is described by Mohr-Coulomb's law. In the spherical cavity-expansion model, a spherically symmetric cavity is expanded from zero initial radius at constant velocity in an infinite medium, which consists of elastic, plastic regions and an additional radially cracked region if the cavity expansion velocity is low. The curves of pressure distribution on the cavity surface and the propagation velocity of interface between the plastic and the elastic region versus the cavity expansion velocity were obtained by an analytic method. The cavity surface pressure obtained from the spherical cavity-expansion models was used to calculate the penetration depth of concrete targets stricken by an olive-nosed rod projectile. Numerical results of different concrete target models were comp.red with the data of empirical equations.
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