Desx extended des was created by the cryptographic security firm rsa security as a modification of the standard des algorithm that supports additional key material , making the algorithm more resistant to brute force attacks than standard des Desx （扩展的des ）是由加密安全公司rsa security在改进标准des算法的基础上创造的，由于该算法支持更长的密钥，因而比标准des算法更能抵抗恶意攻击。
An intrusion detection system ( ids ) is an automated system for the detection of computer system intrusions . the main goal of an ids is to detect unauthorized use , misuse and abuse of computer systems by both system insiders and external intruders 入侵检测系统是指能够自动识别计算机系统内的入侵行为的系统，它可以检测出内部用户或外部入侵者的非授权使用、误用和恶意攻击等异常行为模式，保护计算机系统的安全。
To avoid malicious attacks , the system provided are required to have id verification function and to prevent reproduction and protect intelligence property rights . a digital signature is required before the use of a service . the system should be able to track the invader and set up a blacklist 要求提供的系统具有身份认证功能，以防恶意攻击；享受服务要通过数字签名，以防复制，保护知识产权；系统要能对侵入者进行追踪，以便确定黑名单。
From the point of view of usability in information security , this paper designs a reasonable scheme to resolve the network congestion . then , this paper proposes some approaches to detect and defense the unfair flow or attack flow , and research the technique of ip traceback 本文从信息安全中信息的可用性角度，利用拥塞检测、流量控制、恶意攻击数据流的检测与防护及ip跟踪等技术，力图给出一个较为完整的internet流量控制和确保信息可用性的解决方法。
Utilizing the characteristics of the human visual system , we embed a digital signal into the average value of the four adjacent wavelet coefficients since the average value has better stability than single wavelet coefficient . this method need n ' t original image when the watermark is extracting . experiment results show the effectiveness of this method which is robust to common image process and fragile to malicious attack , i . e . this method can detect the tampered portions 因此，本文利用小波系数均值来嵌入水印，提出了一种基于小波域的图像完整性验证的半脆弱水印算法，在鲁棒性和脆弱性方面达到了很好的平衡，对非恶意攻击有很强的鲁棒性，而对于恶意的篡改操作有很强的识别和定位能力。
The security problem and solution of the special information system in government is discussed in this article . for the threat against the special information system in government comes from inside and outside , how to keep network security and control risk inside . mianyang is a test city of e - government , which is the only city in south - west 电子政务系统同时又是一个相对独立,信息在内、外网分别交流但又与外部密切联系的专用信息系统,恶意攻击或无意泄密可来自内部和外部,正是由于电子政务信息的特殊性质决定了系统网络的安全性显得尤为重要。
Experimental results show that the proposed techniques have good imperceptibility and can survive of common image processing operations and jpeg lossy compression with high robustness . the second one considered the watermarking system as a special digital communication system and introduced the ecc as channel coding technique . by using the turbo coding technique , we are able to reduce the watermark bit error rate and improve the robustness of the watermark so as to make counterfeiting attacks more difficult 本文在保证水印不可见性的基础上和载体图像的允许降质范围内，利用rbf神经网络技术实现数字水印信息的最大强度嵌入以增强数字水印抵御各种恶意攻击的稳健性;在通信论和信息论模型基础上，引入ecc (差错控制编码)技术降低水印的误码率，使得提取水印信息更加可靠，使可能的水印攻击变得更加困难，从而获得更好的水印稳健性和可靠性。
