一种高效的移动云服务环境下隐私保护认证协议

为了解决移动云服务环境的互相认证和隐私保护问题,设计了一种改进的移动云服务环境下隐私保护认证协议.该协议结合基于身份的签密技术和多服务器认证技术,保证用户只需注册一次,就可以访问多个移动云服务提供者,同时认证过程不需要可信第三方参与;该协议在移动终端未使用计算复杂度高的双线性对运算和映射到域上的hash运算,其计算效率显著提高.通过理论分析和实验结果可知:该协议与目前已有的同类协议相比,在移动端的计算时间为45.242 s,其计算效率约为已有同类协议的2倍;具有用户匿名和不可追踪等安全性质;能够抵抗错误口令登录、更改攻击.

一种基于聚类与分割技术的连续数据发布隐私保护方案

数据发布的隐私保护其主要目标是在不泄露用户隐私的情况下提高数据的可用性.数据总是处于不断地变化之中,连续数据发布的隐私保护显得尤为重要.由于静态数据发布的隐私保护方法无法抵抗链接攻击和关键值缺失攻击,因此静态数据发布的隐私保护方法无法直接用于连续数据发布的隐私保护.结合聚类思想以及匿名分割技术提出一种基于分割与聚类的l-diversity算法(l-diversitybased on anatomy and clustering algorithm,LDACA),利用方差计算数据属性的权重,并计算出每条记录的综合值,根据综合值划分等价类,再实现数据的连续发布.实验分析显示,LDACA算法在保证隐私保护能力不变的情况下具有较高的执行效率以及较低的信息损失率.

Efficient Priority Packet Recovery Based on Network Coding in DVB-IPDC System

In DVB-IPDC system, due to the constraints of handheld devices and the broadcast nature of wireless network, packet loss is inevitable. ECDR-NC proposed is a retransmission encoding packet selection algorithm based on the dynamic information updating, which can find the current most effective complete decoding packet. ECDR-NC can not only avoid the redundant encoding packets due to the overlapping among encoding packets, but also reduce the computational complexity compared with the traditional encoding schemes. Furthermore, the retransmission upper bound of ECDR-NC is fully controlled. In time-sensitive applications, to maximize the aggregate number of recovery packets while minimizing the total number of discarded packets due to the time limit according to the priority preference, the adaptive priority scheme EPNC is formulized, and the weighted relation graph is constructed to find the maximum-weighted encoding packets sequence according to the decoding gains. In the same network environment, the performances comparisons between PNC and EPNC show that EPNC is more efficient and more rational, and the average discarded packets ratios ofEPNC can be reduced about 18%~27%. The main contributions of this paper are an effective retransmission encoding packet selection algorithm ECDR-NC proposed, and a new adaptive priority recovery scheme EPNC introduced into DVB-IPDC system.

Lower bounds on the periodic Hamming correlations of frequency hopping sequences with low hit zone

In this paper, several periodic Hamming correlation lower bounds for frequency hopping sequences with low hit zone, with respect to the size p of the frequency slot set, the sequence length L, the family size M, low hit zone LH （ or no hit zone NH ）, the maximum periodic Hamming autocorrelation sidelobe Ha and the maximum periodic Hamming crosscorrelation He, are established. It is shown that the new bounds include the known LempeI-Greenberger bounds, T.S. Seay bounds and Peng-Fan bounds for the conventional frequency hopping sequences as special cases.

New sets of low-hit-zone frequency-hopping sequence with optimal maximum periodic partial Hamming correlation

Recently, Chung et al. gave a general method to construct frequency-hopping sequence set(FHS set) with low-hit-zone(LHZ FHS set) by the Cartesian product. In their paper, Theorems 5 and 8 claim that k FHS sets whose maximum periodic Hamming correlation is 0 at the origin result in an LHZ FHS set based on the Cartesian product, and Proposition 4 presented an upper bound of the maximum periodic Hamming correlation of FHSs. However, their statements are imperfect or incorrect. In this paper, we give counterexamples and make corrections to them. Furthermore, based on the Cartesian product, we construct two classes of LHZ FHS sets with optimal maximum periodic partial Hamming correlation property. It is shown that new FHS sets are optimal by the maximum periodic partial Hamming correlation bound of LHZ FHS set.

On a general class of quadratic hopping sequences

Based upon quadratic polynomials over the finite field, a new class of frequency hopping sequences with large family size suitable for applications in time/frequency hopping CDMA systems, multi-user radar and sonar systems is proposed and investigated. It is shown that the new time/frequency hopping sequences have at most one hit in their autocorrelation functions and at most two hits in their crosscorrelation functions except for a special case, and their family size is much larger than the conventional quadratic hopping sequences. The percentage of full collisions for the new quadratic hopping sequences is discussed. In addition, the average number of hits for the new quadratic hopping sequences, quadratic congruence sequences, extended quadratic congruence sequences and the general linear hopping sequences are also derived.

Global optimum encoding packet selection mechanism based on opportunistic network coding for wireless network retransmission

Packet loss cannot be avoided in wireless network due to wireless transmission medium particularity, therefore improving retransmission efficiency is meaningful to wireless transmission. The current retransmission packet selection mechanisms based on oppornistic network coding （ONC） face low retransmission efficiency and high computational complexity problems. To these problems, an optimized encoding packet selection mechanism based on ONC in wireless network retransmission （OONCR） is proposed. This mechanism is based on mutual exclusion packets and decoding gain concepts, and makes full use of ONC advantages. The main contributions of this scheme are to control the algorithm eomplexity of the maximum encoding packets selection effectively, avoid the redundancy encoding packets due to the overlapping among encoding packets, and take the encoding packet local and global optimization problem into consideration. Retransmission efficiency is evaluated according to the computational complexity, the throughput, the retransmission redundancy ratio, and the number of average retransmission. Under the various conditions, the number of average retransmission of OONCR is mainly lower than that of other typical retransmission packet selection schemes. The average retransmission redundancy ratios of OONCR are lower about 5%-40% compared with other typical schemes. Simultaneously the computational complexity of OONCR is comparatively lower than that of other typical schemes.