普适复合水银承诺方案

水银承诺方案是一般承诺方案的一种有趣变形.水银承诺方案中增加了模糊公开阶段,模糊公开阶段不要求绑定性但是不能与真实的公开阶段冲突.普适复合安全性基本框架最早由Canetti等人提出.普适复合能够保证更高等级的安全性,比如满足普适复合性质即能实现并发安全、自适应安全以及非延展安全等等.文中提出一种普适复合水银承诺方案的构造并且在公共参数模型中证明其安全性.文中的结论一方面深化了水银承诺方案的研究,另一方面回答了Gennaro和Micali提出的一个公开问题.     

分布式网络环境下的跨域匿名认证机制

TPM计算和存储能力的制约以及直接匿名认证（DAA）的复杂性,导致现有的DAA方案只适用于单可信域,针对此局限,提出了一种适合分布式网络并行、高性能及计算机协同工作特点的跨域匿名认证机制。该机制引入可信第三方——证书仲裁中心（CAC）完成跨域示证者的平台真实性验证,为身份真实的示证者颁发跨域认证证书,该证书一次颁发,多次使用,提高跨域匿名认证效率,同时防止CAC成为系统瓶颈。该模型具有高效、安全、可信等特点,且达到可控的匿名性,并通过通用可组合安全模型分析表明该机制安全地实现了跨域匿名认证。     

通用可组合认证密钥交换协议

物理不可克隆函数是指对一个物理实体输入一个激励,利用其不可避免的内在物理构造的随机差异输出一个不可预测的响应．针对传感器节点的计算、存储和通信能力有限等问题,基于物理不可克隆函数提出物理不可克隆函数系统的概念,并在此基础上提出一个新的用于无线传感器网络的认证密钥交换协议,最后在通用可组合框架内给出新协议抵抗静态敌手的安全性证明．相比于传统基于公钥加密的认证密钥交换协议,新协议不使用任何可计算的假设,而是基于物理不可克隆函数系统的安全属性实现,因此在很大程度上减少了计算和通信开销．该协议涉及较少的交互次数,认证协议计算仅仅需要散列函数、对称加密和物理不可克隆函数系统．     

标准模型下通用可组合的口令认证密钥交换协议

通过构造不可延展的、可提取的且是弱模拟可靠的陷门承诺体制,以及相应的平滑投射Hash函数簇,设计了一个高效的通用可组合(universal composable,简称UC)安全的两方口令认证密钥交换(password authenticated key exchange,简称PAKE)协议,并在静态腐化模型下给出了严格的安全性证明.该协议使得PAKE协议在UC框架下达到了最优的两轮.与已有的协议相比,该协议避免了零知识证明协议的使用,在保持计算复杂度相当的前提下有效地提高了通信效率.     

一种改进TSENG-JAN群签名的安全分析

本文对一种改进的Tseng-Jan群签名进行安全性分析,指出了该方案具有广义伪造性和相关性,即任何人可以对任意消息签名,管理员却不能对签名者进行追踪;且能够区分两个不同的签名是否来自于同一个人.     

适用于MANETs的前摄性门限签名协议

现有的门限签名方案存在大量动态的用户集合,不适用于移动Ad-hoc网络(MANETs)。为此,提出一种适用于MANETs网络的高效门限签名协议。该协议的安全性基于标准RSA假设,且满足通用可组合安全性。高效门限签名协议具有前摄性,能够同时提供“分享密钥”和“更新用户子密钥”的功能。安全性分析结果证明该协议的高效性。     

Universally composable and customizable post-processing for practical quantum key distribution

In quantum key distribution (QKD), a secret key is generated between two distant parties by transmitting quantum states. Experimental measurements on the quantum states are then transformed to a secret key by classical post-processing. Here, we propose a construction framework in which QKD classical post-processing can be custom made. Though seemingly obvious, the concept of concatenating classical blocks to form a whole procedure does not automatically apply to the formation of a quantum cryptographic procedure since the security of the entire QKD procedure rests on the laws of quantum mechanics and classical blocks are originally designed and characterized without regard to any properties of these laws. Nevertheless, we justify such concept of concatenating classical blocks in constructing QKD classical post-processing procedures, along with a relation to the universal-composability-security parameter. Consequently, effects arising from an actual QKD experiment, such as those due to the finiteness of the number of signals used, can be dealt with by employing suitable post-processing blocks. Lastly, we use our proposed customizable framework to build a comprehensive generic recipe for classical post-processing that one can follow to derive a secret key from the measurement outcomes in an actual experiment.     

Basing cryptographic protocols on tamper-evident seals

In this article, we attempt to formally study two very intuitive physical models: sealed envelopes and locked boxes, often used as illustrations for common cryptographic operations. We relax the security properties usually required from locked boxes [such as in bit-commitment (BC) protocols] and require only that a broken lock or torn envelope be identifiable to the original sender. Unlike the completely impregnable locked box, this functionality may be achievable in real life, where containers having this property are called “tamper-evident seals”. Another physical object with this property is the “scratch-off card”, often used in lottery tickets. We consider three variations of tamper-evident seals, and show that under some conditions they can be used to implement oblivious transfer, BC and coin flipping (CF). We also show a separation between the three models. One of our results is a strongly fair CF protocol with bias bounded by O(1/r) (where r is the number of rounds); this was a stepping stone towards achieving such a protocol in the standard model (in subsequent work).     

Biodegradable polymers: A review about biodegradation and its implications and applications

Plastic waste pollution is a global environmental problem that could be solved by biodegradable materials. In addition, its biodegradability has been important for medical applications. In this way, the biodegradability performance has been investigated for different materials under diversified environmental conditions. In this context, this review shows the main up-to-date biodegradable polymers (from renewable sources and fossil-based), their structure and properties, and their biodegradability characteristics. Also, this review shows the effect of polymer properties and environmental conditions on biodegradability, methods of biodegradability and toxicity determination, modification processes to enhance biodegradability, and main applications of biodegradable polymers for agriculture, medical, and packaging. Finally, this review presents a discussion of the implications of biodegradation on the environment, the current context, and future perspectives of plastic biodegradation.