2016下半年信息安全工程师上午真题试题解析第71-75题71-75、（1）is the science of hiding information. Whereas the goal of cryptography is to make data unreadable by a third party. the goal of steganography（[ˌstegə'nɒgrəfɪ]隐写术） 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 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 spread spectrum radio communication. With computers and networks, there are many other ways of hiding informations, such as:
Covert channels (c,g, Loki and some distributed denial-of-service tools use the Internet Control （3）Protocol, or ICMP, as the communication channel between the “bad guy”and a compromicyed system)
Hidden text within Web pages
Hiding files in “plain sight”(c,g. what better place to “hide”a file than with an important sounding name in the c:\winnt system32 directory)
Null ciphers(c,g, using the first letter of each word to form a hidden message in an otherwise innocuous text)
steganography today, however, is significantly more （4）than the example about suggest, allowing a user to hide large amounts of information within image and audio. These forms of steganography often are used in conjunction with cryptography so the information is double protected; first it is encrypted and then hidden so that an advertisement first. find the information ( an often difficult task in and of itself) and the decrypted it.
The simplest approach to hiding data within an image file is called （5）signature insertion. In this method, we can take the binary representation of the hidden data and the bit of each byte within the covert image. If we are using 24-bit color the amount and will be minimum and indiscriminate to the human eye.
（1）A、Cryptography
B、Geography
C、Stenography
D、Steganography
（2）A、methods
B、software
C、tools
D、services
（3）A、Member
B、Management
C、Message
D、Mail
（4）A、powerful
B、sophistication（[səˌfɪstɪˈkeɪʃn]可理解为先进）
C、advanced
D、easy
（5）A、least（LSB：least significant bit）
B、most
C、much
D、less
信管网解析：LSB隐写LSB全称least significant bit，最低有效位PNG文件中的图像像数一般是由RGB三原色（红绿蓝）组成，每一种颜色占用8位，取值范围为0x00~0xFF，即有256种颜色，一共包含了256的3次方的颜色，即16777216 种颜色人类的眼睛可以区分约1000万种不同的颜色这意味着人类的眼睛无法区分余下的颜色大约有6777216种LSB隐写就是修改RGB颜色分量的最低二进制位（LSB），而人类的眼睛不会注意到这前后的变化每个像数可以携带3比特的信息信管网参考答案：A、A、C、B、A点击查看：2016下半年信息安全工程师上午综合知识真题
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