网络采购系统中安全机制的研究与实现

针对网络采购系统中的安全问题，提出了一种网络采购系统安全机制模型，综合应用数字证书与ASP.NET的Forms身份验证相结合的认证技术，以及数据加密和数字签名技术，实现了其安全机制。同时，基于B/S模式下实现加密与数字签名的问题，开发了电子合同加密和数字签名智能客户端程序，为构造安全实用的大型网络采购系统奠定了技术基础。     

数字签名在电子商务中的实现

随着电子商务的迅猛发展,数字签名是保证数据完整性的重要技术。重点研究并用Java实现了基于公钥加密机制的数字签名算法。最后对数字签名在电子商务中的发展作了展望。     

公共密钥密码体制在数字签名中的应用

数字签名机制是保证信息安全的一种重要方法。本文简单介绍了公共密钥密码体制在数字签名中的应用，特别是集体签名问题。为了防止公钥被伪造、篡改，还讨论了认证机制。     

一种企业机密文档分发机制

综合利用数字指纹、加密、数字签名等技术，提出了一种局部环境下机密文档的分发机制。该机制不仅可以实现对文档的授权访问，而且当发现被非法分发的文档时，可以确定出非法者并提供证据。该机制设计简单，具有很好的计算和存储效率。     

基于数字签名的WLAN安全机制研究

本文从WLAN安全的几个特点和要素出发,提出了一种新的基于数字签名的WLAN安全机制;该机制针对无线窃听、身份假冒和数据篡改这三个威胁WLAN的不安全因素,分为认证鉴别机制、加密传输机制和消息鉴别与完整性检测机制三个模块进行了研究。     

前向安全的多重数字签名方案

首次将前向安全的概念引入到多重数字签名体制，提出了一个前向安全的多重数字签名方案．方案能实现即使所有签名人的签名密钥被泄露，以前所产生的多重数字签名依然有效．另外，方案是基于Schnorr签名体制构造的，引入了预计算，对多重数字签名的生成速度有所改进．     

基于RSA的XML不可否认签名方法研究*

针对普通XML数字签名的可否认问题,首先介绍了XML数字签名原理,然后分析了RSA签名机制和不可否认签名方案,在此基础上提出了一种改进的不可否认签名算法,并将其应用到XML数字签名结构的签名方法中,从而提出了一种新的XML不可否认签名方法。实验表明,该方法能够确保XML数字签名的不可否认性,是实现XML文档安全交换的一种很有发展前景的保障技术。     

具有消息认证功能的多重数字签名方案

根据具有消息认证功能的数字签名方案设计了两种新的基于离散对数问题的有序多重数字签名方案和广播多重数字签名方案。新的方案具有简单的初始化过程，在签名时具有随机性，在签字和验证方程中无须求逆，且具有消息认证功能。具有更高的实用性和安全性。     

基于RSA的证实数字签名方案

验证者要知道一个证实数字签名的有效性，必须得到一个称为证实者的第3方的帮助与合作。签名者的安全性和证实签名的“不可见性”是一个证实数字签名方案必须具备的两个重要特性。考虑到RSA是应用最广泛的公钥密码体制之一，该文提出了一种完全基于RSA的证实数字签名方案，分析表明，该方案是一种安全高效的证实数字签名实现方案。     

基于零知识证明的XML数字签名方案

数字签名用于保证网络问传送文档的完整性，机密性和不可否认性。XML与数字签名的结合比传统的数字签名更加优越，文章提出了一种用Java实现的基于零知识证明的XML数字签名方案，描述了用数字签名技术对XML文档进行签名及验证的过程。     

一种基于Schnorr体制的同时型多盲签名方案

本文提出了一种基于Schnorr体制的非平凡同时型多盲签名方案，可以同时完成盲签名和同时型多签名尺寸不会随签名人数增加而增加，并对该签名方案的正确性、盲性和不可伪造性作了证明，文章最后给出了一个基于该方案的具体应用。     

Forward-secure identity-based signature: Security notions and construction

The security of traditional identity-based signatures wholly depends on the security of secret keys. Exposure of secret keys requires reissuing all previously assigned signatures. This limitation becomes more obvious today as key exposure is more common with increasing use of mobile and unprotected devices. Under this background, mitigating the damage of key exposure in identity-based signatures is an important problem. To deal with this problem, we propose to integrate forward security into identity-based signatures. In this paper, we firstly formalize the definition and security notions for forward-secure identity-based signature scheme, and then construct an efficient scheme. All parameters in our scheme have, at most, log-squared complexity in terms of the total number of time periods. The scheme is provably secure without random oracles.     

An efficient short certificate-based signature scheme

Certificate-based cryptography combines the merits of traditional public key infrastructure (PKI) and identity-based cryptography. It does not have the key escrow problem in identity-based cryptography, and eliminates the certificate revocation problem and third-party queries in traditional PKI. In this paper, we first refine the security model of certificate-based signatures introduced in EuroPKI’07. We then present a short certificate-based signature scheme, which is proven to be existentially unforgeable against adaptive chosen message attacks in the random oracle model. Our scheme requires only one pairing operation (and three pre-computable pairing operations) in signature generation and verification. In addition, the signature size of our scheme is only one group element. To the best of our knowledge, the signature size of our scheme is the shortest and the computational cost is the lowest when compared with other concrete certificate-based signature schemes in the literature. This makes our scheme possess strong applicability in situations with limited bandwidth and power-constrained devices.     

一个基于离散对数和因子分解的数字签名方案的分析

邵祖华提出了一个同时基于离散对数问题(DLP)和因子分解问题(FP)两个数学难题的数字签名方案[1](Shao Signature Scheme),但是该方案的安全性仅仅依赖于因子分解问题[2],任俊伟和林东岱对其进行了改进[3].指出改进的数字签名方案的一个错误并对其安全性进行分析,证明当离散对数可解时改进方案是不安全的.     

一个基于环签名的英式电子拍卖协议

提出了一个基于双线性对的环签名方案,该方案具有如下特点:(1)签名者的身份可通过管理员追踪;(2)管理员的身份追踪权能被分享;(3)当签名中用于追踪签名人部分的内容为空时,它依然是一个具有无条件匿名性的环签名方案;(4)保留了环签名较群签名灵活和有效的优点。最后利用该方案对Omote和Miyaji的英式电子拍卖协议进行改进,克服了原协议中参加同一次拍卖的投标者的多次投标能被跟踪的缺点。     

A new convertible authenticated encryption scheme with message linkages

In this article, we present an authenticated encryption scheme with message linkages used to deliver a large message. To protect the receiver’s benefit, the receiver can easily convert the signature into an ordinary one that can be verified by anyone. Several feasible attacks will be discussed, and the security analysis will prove that none of them can successfully break the proposed scheme.     

Schnorr方案推广及其在格密码学中的应用

Schnorr身份认证方案是密码学中的经典方案,可以推广到很多其他数学问题(如离散对数问题)上,从而构造出在标准模式中安全的身份认证方案,并且可以通过Fiat-Shamir转换工具,将其转换为在随机谕示模式中安全的数字签名方案。但将上述转换方法用于基于格的密码学中时会出现一些特殊现象(如方案中止现象)。为此,通过矩阵表示方法分析Schnorr方案的构造方法,得出其构造方法成立的充要条件,从而使其可在更大范围内构造出安全的类Schnorr方案。根据类Schnorr方案,分析基于格的身份认证方案中的方案中止现象,并通过数学方法证明,对于某些身份认证方案(如∑-身份认证方案),其中的方案中止现象不可避免,该结论为深入研究基于格的密码学提供了参考依据。     

Optimal resilient threshold GQ signatures

GQ signature scheme is widely used in many cryptographic protocols, such as forward-secure signature scheme, identity-based signature scheme, etc. However, there is no threshold version of this important signature scheme in the open literature. We proposed the first threshold GQ signature scheme. The scheme is proved unforgeable and robust against any adaptive adversary by assuming hardness of computing discrete logarithm modulo a safe prime and existence of fully synchronous broadcast channel. Furthermore, with some modifications, our scheme achieves optimal resilience such that the adversary can corrupt up to a half of the players. As an extension of our work, we provided a threshold identity-based signature scheme and a threshold forward-secure signature scheme, which is the threshold version of the most efficient forward-secure signature scheme up to now.     

Security weaknesses of a signature scheme and authenticated key agreement protocols

At ACISP 2012, a novel deterministic identity-based (aggregate) signature scheme was proposed that does not rely on bilinear pairing. The scheme was formally proven to be existentially unforgeable under an adaptive chosen message and identity attack. The security was proven under the strong RSA assumption in the random oracle model. In this paper, unfortunately, we show that the signature scheme is universally forgeable, i.e., an adversary can recover the private key of a user and use it to generate forged signatures on any messages of its choice having on average eight genuine signatures. This means, that realizing a deterministic identity-based signature scheme in composite order groups is still an open problem. In addition, we show that a preliminary version of the authenticated key exchange protocol proposed by Okamoto in his invited talk at ASIACRYPT 2007 is vulnerable to the key-compromise impersonation attack and therefore cannot be secure in the eCK model. We also show that the two-party identity-based key agreement protocol of Hölbl et al. is vulnerable to the unknown key-share attack.     

Design of DL-based certificateless digital signatures

Public-key cryptosystems without requiring digital certificates are very attractive in wireless communications due to limitations imposed by communication bandwidth and computational resource of the mobile wireless communication devices. To eliminate public-key digital certificate, Shamir introduced the concept of the identity-based (ID-based) cryptosystem. The main advantage of the ID-based cryptosystem is that instead of using a random integer as each user’s public key as in the traditional public-key systems, the user’s real identity, such as user’s name or email address, becomes the user’s public key. However, all identity-based signature (IBS) schemes have the inherent key escrow problem, that is private key generator (PKG) knows the private key of each user. As a result, the PKG is able to sign any message on the users’ behalf. This nature violates the “non-repudiation” requirement of digital signatures. To solve the key escrow problem of the IBS while still taking advantage of the benefits of the IBS, certificateless digital signature (CDS) was introduced. In this paper, we propose a generalized approach to construct CDS schemes. In our proposed CDS scheme, the user’s private key is known only to the user himself, therefore, it can eliminate the key escrow problem from the PKG. The proposed construction can be applied to all Discrete Logarithm (DL)-based signature schemes to convert a digital signature scheme into a CDS scheme. The proposed CDS scheme is secure against adaptive chosen-message attack in the random oracle model. In addition, it is also efficient in signature generation and verification.