（1）is the science of hiding information.Where as the goal of cryp to graphy is to make data unreadable by a third party.the goal of steganography is to hide the data from a third party.In this article,I will discuss what steganography is,what purposes it serves,and will provide an example using available software. There are a large number of steganographic（2）that most of us are familiar with(especially if you watch a lot of spymovies),ranging from invisible inkandmicrodotstosecretingahiddenmessageinthesecondletterofeachwordofalargebodyoftextandspreadspectrumradiocommunication.With computersandnetworks,there arem any other ways of hiding informations,suchas: Covertchannels(c,g,Lokiandsomedistributeddenial-of-servicetoolsusetheInternetControl（3）Protocol,orICMP,asthecommunicationchannelbetweenthe“badguy”andacompromicyedsystem) HiddentextwithinWebpages Hidingfilesin“plainsight”(c,g.whatbetterplaceto“hide”afilethanwithanimportantsoundingnameinthec:\winntsystem32directory) Nullciphers(c,g,usingthefirstletterofeachwordtoformahiddenmessageinanotherwiseinnocuoustext) steganographytoday,however,issignificantlymore（4）than the example about suggest,allowing ausertohidelargeamountsofinformationwithinimageandaudio.Theseformsofsteganographyoftenareusedinconjunctionwith cryptographysothe information is double protected;firstitisencryptedandthenhiddensothatanadvertisementfirst.find the information(an often difficult task inandofitself)and the decryptedit. The simple stapproachtohidingdatawithinanimagefileiscalled（5）signatureinsertion.In this method,we can take the binaryrepresentationofthehiddendataandthebitofeachbytewithinthecovertimage.If weareusing 24-bitcolor the amount and will be minimum and indiscriminate to the human eye.

（1）is the science of hiding information.Where as the goal of cryp to graphy is to make data unreadable by a third party.the goal of steganography is to hide the data from a third party.In this article,I will discuss what steganography is,what purposes it serves,and will provide an example using available software. There are a large number of steganographic（2）that most of us are familiar with(especially if you watch a lot of spymovies),ranging from invisible inkandmicrodotstosecretingahiddenmessageinthesecondletterofeachwordofalargebodyoftextandspreadspectrumradiocommunication.With computersandnetworks,there arem any other ways of hiding informations,suchas: Covertchannels(c,g,Lokiandsomedistributeddenial-of-servicetoolsusetheInternetControl（3）Protocol,orICMP,asthecommunicationchannelbetweenthe“badguy”andacompromicyedsystem) HiddentextwithinWebpages Hidingfilesin“plainsight”(c,g.whatbetterplaceto“hide”afilethanwithanimportantsoundingnameinthec:\winntsystem32directory) Nullciphers(c,g,usingthefirstletterofeachwordtoformahiddenmessageinanotherwiseinnocuoustext) steganographytoday,however,issignificantlymore（4）than the example about suggest,allowing ausertohidelargeamountsofinformationwithinimageandaudio.Theseformsofsteganographyoftenareusedinconjunctionwith cryptographysothe information is double protected;firstitisencryptedandthenhiddensothatanadvertisementfirst.find the information(an often difficult task inandofitself)and the decryptedit. The simple stapproachtohidingdatawithinanimagefileiscalled（5）signatureinsertion.In this method,we can take the binaryrepresentationofthehiddendataandthebitofeachbytewithinthecovertimage.If weareusing 24-bitcolor the amount and will be minimum and indiscriminate to the human eye.

在DES算法中，需要进行16轮加密，每一轮的子密钥长度为（）

67mod119的逆元是（）

AES结构由以下4个不同的模块组成，其中（）是非线性模块

杂凑函数SHAI的输入分组长度为（）比特

设在RSA的公钥密码体制中，公钥为（c，n）=（13,35），则私钥为（）

两个密钥三重DES加密：C=CK1[DK2[EK1[P]]],K1≠K2，其中有效的密钥为（）

包过滤技术防火墙在过滤数据包时，一般不关心（）

以下关于网络流量监控的叙述中，不正确的是（）

以下关于VPN的叙述中，正确的是（）