72.is the science of hiding information.Whereas.the goal of cryptography is tomake dataulueadable by a third party,the goal of steganography is to hide the data from athirdparty.In this article,I will discuss what steganography is;what purposes it serves,and will provide an example using available software.
There is?a large number of steganographic（）that most of us are familiar with(especially if you watch a lot of spy movies!),ranging from invisible ink and microdots to?secreting a hidden message in the second letter of each word of a large body of text and?spreads?spectrum radio communication.With computers and networks,there are many other ways of hiding information,such as:
>Covert channels(e.g.,Loki and some distributed denial-of-service tools use the Internet Control（）Protocol,or ICMP,as the communications?channel?between the"bad guy"and a compromised system)
>Hidden text within web pages
>Hiding files in"plain?sight"(e.g.,what better place to"hide a file than with an important sounding name in the c:\winnt\system32 directory?）
>Null ciphers(e.g.,using the first letter of each word?to?from?a?hidden message in and otherwise innocuous text)
Steganography today,however,is significantly more（）than the examples above suggest,allowing a user to hide large amounts of infromation within image and audio files.these forms of steganography often are used in conjunction with cryprography so that the information is doubly protected;first it is encrypted and then hidden so that an adversary has to first find the information(an often difficult task in and of itself)and then?decrypt it.
The simplest approach to hiding data within an image flile is callde（）significant bit insertion in this method we can take the binary?representation of the hidden data and overwirit the bit of each byte within the cover image.if we are using 24-bit color the amount of change?well be mininmal and indiscerible to the human?eye.
问题1选项
A.Cryptography
B.Geography
C.Stenography
D.Steganography
问题2选项
A.methods
B.Softeare
C.Tools
D.Services
问题3选项
A.Member
B.management
C.message
D.Mail
问题4选项
A.powerful
B.Sophisticated
C.Advancde
D.easy
问题5选项
A.lesast
B.Most
C.Muchu
D.less
