DES-GENERATED CHECKSUMS FOR ELECTRONIC SIGNATURES

Secrecy and authentication are two important features of a secure communication system. Public Key Cryptosystems, based, e.g., on the Rivest-Shamir-Adleman (RSA) algorithm, provide a very elegant solution to the problem of authenticity verification or true electronic signatures. Practical problems, however, mainly the lack of execution speed, prevent a straightforward application. In order to sign a long message it is much faster to first calculate a short digest or checksum and then sign the compressed message. For this checksum calculation the fast, inexpensive and extensively tested Data Encryption Standard (DES) can be used. But care must be taken that this additional processing step does not introduce any weakness into the signature scheme. This paper investigates two DES-based hashing methods. It is shown that neither method seems to introduce any statistical regularities in the generated checksums. The “Cipher/Message to Plain Feedback,” however, is not secure under a modification compensation attack. It is further shown how the second method, the “Cipher to Plain Feedback” proposed by Davies and Price, can be broken by a “meet in the middle attack.” This checksum method, however, can be used safely with a slight modification.     

Chaos-based selective encryption for H.264/AVC

Encryption techniques are usually employed to maintain the secrecy of the video streams transmitted via a public network. However, full encryption using strong cryptographic algorithms is usually not necessary if the purpose is to destroy the commercial value by preventing pleasant viewing. For this purpose, selective encryption is preferred as its operating efficiency is higher. Here, a chaos-based selective encryption scheme implemented on the H.264/AVC standard is proposed. The scheme employs multiple Rényi chaotic maps to generate a pseudorandom bit sequence which is used to mask the selected H.264/AVC syntax elements. It provides sufficient protection against full reconstruction while keeping the format compliance property so as not to cause decoding error without the key. The operating efficiency is high due to the low computational complexity of the Rényi chaotic map, as justified by the simulation results using video clips at various resolutions. Moreover, the security analyses show that the proposed algorithm is highly sensitive to the secret key and possesses good perceptual security.     

Experiences in developing a fair-exchange e-commerce protocol using common off-the-shelf components

Fair-exchange is an important property that must be ensured in all electronic commerce environments where the merchants and the customers are reluctant to trust each other. This property guarantees that none of the transacting parties suffer because of the fraudulent behavior of the other party in the transaction. In this paper, we describe our experiences in developing a new e-commerce protocol to address the problem of fair-exchange for digital products. The protocol is based on a novel cryptographic technique that we had proposed earlier. We show how to use common off-the-shelf software components to develop such a protocol.     

智能文电传输终端的设计制作

本文针对机要保密通信要求的现状,设计了一种基于Intel的PXA255和CPLD芯片,Linux操作系统,采用安全性较高的PSTN网络进行通讯,使用AES和RSA加密算法对信息进行加密传输的嵌入式产品方案。实现了文件、传真的加密传输,并提供丰富的办公环境和友好的人机界面。针对系统外部设备的实际应用,提出了采用CPLD来控制外部设备的设计方案。针对系统高保密的要求,在终端系统中采用密钥破碎和密钥随机生成技术,实现信息传输的一传一密。     

网络通讯中信息安全性分析

确保网络通讯中信息安全的主要技术是加密技术。在论述了信息加密技术的基础上,进一步分析了加密技术在网络通讯中的应用,最后介绍了网络信息加密技术的发展方向。     

Optimal quantitative cryptanalysis of permutation-only multimedia ciphers against plaintext attacks

Recently, an image scrambling encryption algorithm of pixel bit based on chaos map was proposed. Considering the algorithm as a typical binary image scrambling/permutation algorithm exerting on plaintext of size M×(8N), this paper proposes a novel optimal method to break it with some known/chosen-plaintexts. The spatial complexity and computational complexity of the attack are only O(32·MN) and O(16·n₀·MN) respectively, where n₀ is the number of known/chosen-plaintexts used. The method can be easily extended to break any permutation-only encryption scheme exerting on plaintext of size M×N and with L different levels of values. The corresponding spatial complexity and computational complexity are only O(MN) and O(⌈log_L(MN)⌉·MN) respectively. In addition, some specific remarks on the performance of the image scrambling encryption algorithm are presented.     

电子商务安全的研究分析

本文主要介绍了电子商务的安全目标，并重点介绍电子商务安全性的实现。     

随机数在加密技术中的应用分析

加密技术是一种重要的信息系统安全技术，本文介绍了随机数的概念以及其在加密技术中的重要作用和主要应用。     

3G系统全网安全体制的探讨与分析

文章基于3GPP体制探讨了3G系统的安全机制，重点分析了3G认证与密钥分配协议、加密与完整性保护的过程及其安全性，并针对核心网部分，从ATMPRM出发讨论了将安全功能置于ATM协议栈中不同位置时的几种安全方案。     

冶金企业中网络数据信息安全研究

研究了冶金企业数据信息对内对外的安全性：数据信息对外的安全性通过防火墙和虚拟专用网技术(VPN)实现，对内的信息安全通过数据加密和数字签名技术来保证。文中重点研究了数据加密技术和数字签名技术，并给出了混合加密和数字签名联合使用的实现策略，该策略已在数家冶金企业中实施并得到检验。