In a secret-sharing scheme,a secret value is distributed among a set of participants by giving each participant a share.The requirement is that only predefined subsets of participants can recover the secret from their shares.The family of the predefined authorized subsets is called the access structure.An access structure is ideal if there exists a secret-sharing scheme realizing it in which the shares have optimal length,that is,in which the shares are taken from the same domain as the secrets.Brickell and Davenport proved that ideal access structures are induced by matroids.Subsequently,ideal access structures and access structures induced by matroids have received a lot of attention.Seymour gave the first example of an access structure induced by a matroid namely the Vamos matroid,that is non-ideal.Since every matroid is multipartite and has the associated discrete polymatroid,in this paper,by dealing with the rank functions of discrete polymatroids,we obtain a sufficient condition for a multipartite access structure to be ideal.Furthermore,we give a new proof that all access structures related to bipartite and tripartite matroids coincide with the ideal ones.Our results give new contributions to the open problem,that is,which matroids induce ideal access structures.
Coin-flipping protocols allow mutually distrustful parties to generate a random bit with uniform distribution.Minimizing bias and keeping fairness are two key requirements in designing such protocols.However,the best previously known fair coin-flipping protocol only guarantees with bias Ο(1 /r).In the paper,we introduce a new approach for fair coin-flipping protocol construction by using Garay et al's "resource fairness" technique and propose a resource-fair two-party coin-flipping protocol according to the standard real/ideal simulation paradigm.Compared with the other coin-flipping protocols,our protocol enjoys an important advantage that its bias is 0.
Self-certified signcryption can remove key escrow problem and certification management problem.Based on Boneh and Boyen's short signature scheme,a secure self-certified signcryption scheme is proposed.Under the strong Diffie-Hellman assumption,the new scheme is proved secure,in which it satisfies public verifiability and existential unforgeablity.Furthermore,performance analysis shows that the proposed scheme only requires two pairing evaluations,so it can be used in the power and bandwidth limited environments.
蜜罐服务的负载均衡是保障蜜场系统稳定运行的关键技术之一.蜜场环境下网络流量具有突发性强、流量大等特点,现有负载均衡算法往往需要动态且频繁地查询采集服务器的负载信息,会增加大量额外的开销.本文提出了一种面向蜜场环境的负载均衡算法(a load balanc algorithm towards the Honey farm environment,LBHF),该算法通过设计预警收敛流量分配策略、主动抢占式反馈策略以及基于排队模型的等待队列动态调整策略,有效地实现了蜜场环境下的负载均衡.实验结果显示,与Pick-KX算法相比LBHF具有良好的性能表现.
The characteristics of the wireless network determinethe requirement of lightweight cryptography. Towards the hugecost of an existing algorithm such as MD5, this paper proposes amessage digest scheme based on the RC4 algorithm which broadens the application area of the RC4 and decreases the requirementof resource or cost. To test the randomicity of the algorithm's digest, fifteen kinds of randomicity test to NIST randomicity teststandard had been done, and the comparative analysis whichcompares the digest's randomicity of the algorithm with MD5 hadbeen performed as well. The performance of the algorithm hadbeen analyzed in aspects of mono-directivity, randomicity, practicality and complexness. Statistic tests and analysis results illustrated that our scheme was of low cost of computing, good statisticperformance, high running speed and lightweight.
