Non-3GPP对EPS的安全接入研究

Non-3GPPN络安全接入EPS是未来异构网络融合的重要基础。本文介绍了Non-3GPPN络接入时EPS系统的安全架构、可信的Non-3GPP网络接入EPS系统的认证机制、密钥协商流程等。     

How Many Queries are Needed to Distinguish a Truncated Random Permutation from a Random Function?

An oracle chooses a function f from the set of n bits strings to itself, which is either a randomly chosen permutation or a randomly chosen function. When queried by an n-bit string w, the oracle computes f(w), truncates the m last bits, and returns only the first \(n-m\) bits of f(w). How many queries does a querying adversary need to submit in order to distinguish the truncated permutation from the (truncated) function? In Hall et al. (Building PRFs from PRPs, Springer, Berlin, 1998) showed an algorithm for determining (with high probability) whether or not f is a permutation, using \(O(2^{\frac{m+n}{2}})\) queries. They also showed that if \(m < n/7\), a smaller number of queries will not suffice. For \(m > n/7\), their method gives a weaker bound. In this note, we first show how a modification of the approximation method used by Hall et al. can solve the problem completely. It extends the result to practically any m, showing that \(\varOmega (2^{\frac{m+n}{2}})\) queries are needed to get a non-negligible distinguishing advantage. However, more surprisingly, a better bound for the distinguishing advantage, which we can write, in a simplified form, as \(O\left( \min \left\{ \frac{q^2}{2^n},\,\frac{q}{2^{\frac{n+m}{2}}},\,1\right\} \right) ,\) can be obtained from a result of Stam published, in a different context, already in 1978. We also show that, at least in some cases, this bound is tight.     

基于隐私推断Non-ⅡD联邦学习模型的后门攻击研究

联邦学习安全与隐私在现实场景中受数据异构性的影响很大,为了研究隐私推断攻击、后门攻击与数据异构性的相互作用机理,提出一种基于隐私推断的高隐蔽后门攻击方案。首先基于生成对抗网络进行客户端的多样化数据重建,生成用于改善攻击者本地数据分布的补充数据集;在此基础上,实现一种源类别定向的后门攻击策略,不仅允许使用隐蔽触发器控制后门是否生效,还允许攻击者任意指定后门针对的源类别数据。基于MNIST、CIFAR 10和YouTube Aligned Face三个公开数据集的仿真实验表明,所提方案在数据非独立同分布的联邦学习场景下有着较高的攻击成功率和隐蔽性。     

Efficient Selective Identity-Based Encryption Without?Random Oracles

We construct two efficient Identity-Based Encryption (IBE) systems that admit selective-identity security reductions without random oracles in groups equipped with a bilinear map. Selective-identity secure IBE is a slightly weaker security model than the standard security model for IBE. In this model the adversary must commit ahead of time to the identity that it intends to attack, whereas in an adaptive-identity attack the adversary is allowed to choose this identity adaptively. Our first system—BB₁—is based on the well studied decisional bilinear Diffie–Hellman assumption, and extends naturally to systems with hierarchical identities, or HIBE. Our second system—BB₂—is based on a stronger assumption which we call the Bilinear Diffie–Hellman Inversion assumption and provides another approach to building IBE systems.     

Thermal Noise Random Number Generator Based on LFSR

With the rapid development of cryptography, the strength of security protocols and encryption algorithms consumedly relies on the quality of random number. In many cryptography applications, higher speed is one of the references required. A new security random number generator architecture is presented. Its philosophy architecture is implemented with FPGA, based on the thermal noise and linear feedback shift register（LFSR）. The thermal noise initializes LFSRs and is used as the disturbed source of the system to ensure the unpredictability of the produced random number and improve the security strength of the system. Parallel LFSRs can produce the pseudo-random numbers with long period and higher speed. The proposed architecture can meet the requirements of high quality and high speed in cryptography.     

Merkle’s Key Agreement Protocol is Optimal: An $$O(n^2)$$ Attack on Any Key Agreement from Random Oracles

We prove that every key agreement protocol in the random oracle model in which the honest users make at most n queries to the oracle can be broken by an adversary who makes \(O(n^2)\) queries to the oracle. This improves on the previous \({\tilde{\Omega }}(n^6)\) query attack given by Impagliazzo and Rudich (STOC ’89) and resolves an open question posed by them. Our bound is optimal up to a constant factor since Merkle proposed a key agreement protocol in 1974 that can be easily implemented with n queries to a random oracle and cannot be broken by any adversary who asks \(o(n^2)\) queries.     

On the Selection of Random Numbers in the ElGamal Algorithm

Generally speaking, parameter selection in all cryptographic algorithms and protocols is a mixture of art and science and exerts various subtle influences on a system, which is related to application requirements, security policies, the compromise between security and the overheads of computation, storage and communications, the balance between security and availability, and to the efficiency of software /hardware implementation, etc. Usually, simplistic, insecure or impractical textbook crypto…     

Improved Ternary-tree Algorithm for Contention Resolution over Random Multi-access Channel

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On the Selection of Random Numbers in the EIGamal Algorithm

The EIGamal algorithm, which can be used for both signature and encryption, is of importance in public-key cryptosystems. However, there has arisen an issue that different criteria of selecting a random number are used for the same algorithm. In the aspects of the sufficiency, necessity, security and computational overhead of parameter selection, this paper analyzes these criteria in a comparative manner and points out the insecurities in some textbook cryptographic schemes. Meanwhile, in order to enhance security a novel generalization of the EIGamal signature scheme is made by expanding the range of selecting random numbers at an acceptable cost of additional computation, and its feasibility is demonstrated.     

Pseudo Random Number Generator Based on Back Propagation Neural Network

Random numbers play an increasingly important role in secure wire and wireless communication. Thus the design quality of random number generator（RNG） is significant in information security. A novel pseudo RNG is proposed for improving the security of network communication. The back propagation neural network（BPNN） is nonlinear, which can be used to improve the traditional RNG. The novel pseudo RNG is based on BPNN techniques. The result of test suites standardized by the U.S shows that theRNGcan satisfy the security of communication.     

单层超晶格Ga_(0.47)In_(0.53)As/InP(110)及半导体合金Ga_(0.235)In_(0.765)P_(0.5)As_(0.5)的状态密度及介电常数(英文)

The DOS, JDOS and ε2(Ω) of monolayer superlattice Ga0.47ln0.53As/ InP(110) have been calculated by a tight-binding approach and compared with that of alloy Ga0.235ln0.765P0.5As0.5 which has the same stoi-chiometric composition as the monolayer superlattice. By using the techniques of the group theory we have obtained the expressions of momentum matrix elements between valence band states and conduction band states with four adjustable parameters. These parameters are determined by fitting the calculated values of ε2(Ω) with the experimental values for InP, GaAs and InAs. Our results show that the superlattice periodicity makes its DOS, JDOS and ε2(Ω) different from those of alloy in varying degree. Due to the folding of Brillouin zone, the JDOS of superlattice turns round in comparison with that of alloy. The momentum matrix elements have different effects for the superlattices and alloys.For the alloys, they can only change the amplitudes of peaks but not the positions of peaks; however, for the superlattices both amplitude and position can be changed.     

(Sr_(0.5)Ba_(0.5))_(1.9)Ca_(0.1)NaNb_(5–x)TaxO_(15)陶瓷的介电性能

通过Ta掺杂改性钨青铜陶瓷(Sr0.5Ba0.5)1.9Ca0.1NaNb5–xTaxO15(x=0～0.30),分析了Ta掺杂量对其烧结性能、微观结构及介电性能的影响。陶瓷的烧结温度随x的增大略有提高。当x<0.10时,陶瓷的tC和弛豫性变化不大;当x≥0.10时,tm(1kHz)明显降低,从270℃(x=0)降低至231℃(x=0.30)。且tm随频率增加向高温移动,弛豫性明显增强。认为Ta掺杂引起其性能变化是由于Ta—O键与Nb—O键键能的差异,导致陶瓷氧八面体中心离子位移量以及A位离子有序程度的变化所致。     

掌上电脑(PPC)与个人数字助理(PDA)

由于PDA很少被提及，所以人们对这个概念知之甚少。往往把商务通、文曲星、快译通、宝典等名字同掌上电脑联系起来。但这些就是掌上电脑吗？答案是否定的。这些市场上流行的所谓“掌上电脑”实际上是PDA，而不是真正的掌上电脑（PPC）。 1．概念不同。PDA是一种用于处理个人事务的数字设备。市场上的PDA产品主要可分为电子词典和电子记事本两类。PPC是电脑家族中的一员，而且是可以放在手掌上的电脑。它提供可供用户使用的各种软件、通信设备，是具有Internet浏览功能的真正的个人电脑。 2．硬件性能有别。这主要是表现在操作系统和…     

声表面波(SAW)传感器(三)

5.声表面波加速度传感器处于加速度场中的物体都要受到惯性力的作用,这是物理力学的基本概念,所以制作的SAW振荡器的基片受到这种惯性力的作用而发生形变,使声表面波传播速度产生变化,从而导致振荡器的频率变化.基片自身的质量小,所以要外加惯性质量块,才能大大提高灵敏度.过去几年中,已经设计并试制了四种不同结构的SAW加速度计,并研究了它们各自的特性.四种结构虽不同,但所受到的惯性力有二类情况:一类是感受器件受     

声表面波(SAW)传感器(二)

三、声表面波电压传感器在声表面波延迟线的输入和输出换能器间的传播途径压电基片上,施加偏置电场,引起弹性形变,产生改变了延迟时间的效应.利用这种效应于电压测试技术开发了声表面波电压传感器.这种当电场施加于压电材料时,所感应产生的弹性形变S以张量形式给出如下公式:S_(ij)=d(ijk)×E_k i,j=x,y,z (6)式中,d_(ijk)是在K方向施加电场E_k时在i平面上沿j方向的压电常数.图12给出了SAW延迟线被施加偏置电场的示意图.如式(6)所示,电场感应产生弹性形变是基本工作原理,而对于电压传感器有效的弹性形变量为S_(xx)或S_(yy),给出常用的三种材料:PCM压电陶瓷,     

声表面波(SAW)传感器(一)

声表面波(SAW)传感器具有许多独特的优点,引起了人们的极大兴趣.本文简要介绍了这类器件的典型应用及其特性原理.     

高介电(1–x)Ca_(0.7)Nd_(0.2)TiO_(3-x)Ba_(0.4)Sr_(0.6)TiO_3陶瓷微波介电特性

采用固相反应法制备了具有钙钛矿结构的(1–x)Ca_(0.7)Nd_(0.2)TiO_(3-x)Ba_(0.4)Sr_(0.6)TiO_3(0.05≤x≤0.5)陶瓷,并对其烧结行为、相组成、显微结构及微波介电性能进行了研究。结果表明:随着(Ba0.4Sr0.6)2+含量的增加,(1–x)Ca_(0.7)Nd_(0.2)TiO_(3-x)Ba_(0.4)Sr_(0.6)TiO_3(0.05≤x≤0.5)陶瓷的品质因数(Q·f)及谐振频率温度系数(τf)单调递减,而相对介电常数(εr)先升后小幅降低。当x=0.2,且烧结温度为1 450℃时,该介质陶瓷的微波介电性能为:εr=151.3,Q·f=5 900 GHz,τf=399.4×10–6/℃。与CaTiO_3(εr=160,Q·f=6 800 GHz,τf=850×10–6/℃)相比,Q·f和εr略微降低,τf有较大程度的减少,故此陶瓷体系有望替代CaTiO_3成为新一类高介电性微波陶瓷。     

sol-gel法制备Ba_(3.99)Sm_(9.34)Ti_(18)O_(54)微波介质陶瓷

以柠檬酸为络合剂,通过sol-gel法制备了Ba3.99Sm9.34Ti18O54陶瓷前驱体;经1100℃预烧2h压片成型后,再在1300℃保温3h,即得到了烧结致密的陶瓷样品。与传统固相法相比,其烧结温度降低了50℃,且陶瓷晶粒细小,晶粒分布均匀,具有更加优良的微波介电性能:εr=79.56,Q·f=9636GHz(4.71GHz),τf=–1.23×10–6/℃。     

SrAl_(12)O_(19)晶体中Nd~(3 )的受激发射

资料[1,2]曾报道过MeO-Al_2O_3(Me为Ca,Sr和Ba)氧化物系统的激光晶体探索研究工作。本文是这一探索研究工作的继续,介绍掺Nd~(3 )的SrAl_(12)O_(19)(SrO·6Al_2O_3)晶体激光器的某些主要振荡光谱特性。SrAl_(12)O_(19)晶体结晶成六角晶系,熔点为1950±30℃。SrAl_(12)O_(19)的透光波段为0.2～5.8微米(晶片厚度≈1毫米时)。这种晶体在(0001)平面具有完美的解理面,其特点是系数N_g=1.702,N_p=1.694。与SrAl_4O_7比较,SrAl_(12)O_(19)晶体的钕分布     

可视数据(Videotex) 实验系统(一)

当前,世界正面临着新的技术革命,其最重要的特征之一是社会信息量和人们对信息的需求急剧增长,促使信息科学技术迅速发展。在这种形势下,如何充分利用现有的技术手段,开拓新型的信息传输业务以满足各方面的需要,是有很大的实际意义的。