（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 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 spectrumradio 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 toolsuse the Internet Control （3）Protocol, or ICMP, as the communicationchannel 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 of tenare 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 C、advanced D、easy

（5）A、least B、most C、much D、less

正确答案：A、A、C、A、A

试题解析：

密码学是一门隐藏信息的科学。而密码学的目标是让第三方无法读取数据。隐写术的目标是从第三方隐藏数据。在这篇文章中，我将讨论隐写术是什么，它的作用是什么，并将提供一个使用现有软件的例子。

有许多我们大多数人都熟悉的隐写术方法（特别是如果你看了很多间谍电影），从看不见的墨水和微粒到在第二个隐藏信息的隐藏。每个字的字母都是一个大正文，传播频谱和无线电通信。在计算机和网络中，隐藏信息的方法有很多，例如：隐藏通道（C、G、Loki和一些分布式拒绝服务工具，如Internet控制消息协议，或ICMP，作为“坏人”和复杂系统之间的通信通道）隐藏网页中的文本隐藏在“清晰可见”的文件中。“（c，g.在c:\winnt system32目录中有一个听起来很重要的名字，“隐藏”一个文件的最佳位置）空密码（c，g，使用每个单词的第一个字母在其他无害的文本中形成一个隐藏的信息），然而，今天的隐写术比建议的例子要强大得多，允许用户隐藏lar图像和音频中的GE信息量。泰纳的这些形式的隐写术与密码学结合使用，因此信息是双重保护的；首先它是加密的，然后是隐藏的，以便广告首先。找到信息（通常是很困难的任务）并对其进行解密。

在图像文件中隐藏数据的最简单方法称为最小签名插入。在这种方法中，我们可以取隐藏数据的二进制表示和隐藏图像中每个字节的位。如果我们使用的是24位颜色，那么对人眼来说，它的量是最小的，也是不加区别的。

 

2017年上半年上午真题71-75

试题解析：有不同的方法来执行基于IP的DoS攻击。最常见的基于IP的DoS攻击是攻击者发送大量连接建立请求（例如，TCP SYN请求）以建立与控制器或DPS的挂起连接。这样，攻击者就可以使用合法用户应该可以使用的网络资源。在其他情况下，攻击者通过用随机值欺骗全部或部分头字段，向数据平面插入大量假的数据包。这些传入的数据包将触发表未命中，并向网络控制器发送大量数据包流请求消息，以使控制器资源饱和。在某些情况下，获得DPS访问权的攻击者可以在流请求消息中人为地生成大量随机包，以使控制通道和控制器资源饱和。此外，DPSS之间缺乏多样性，推动了此类攻击的快速传播。传统的移动回程设备固有地受到保护，以防止由于复杂和供应商特定的设备而导致的攻击传播。此外，传统回程设备不需要以类似于DPSS与中央控制器通信的方式与核心控制设备频繁通信。这些特性最小化了DoS攻击的影响和传播。此外，传统的回程设备是由多个网络元素共同控制的。例如，单个长期逐出（LTE）enodeb__连接高达32 mmes。因此，对单个核心元素的DoS/DDOS攻击不会终止网络回程设备的整个操作。

 

Trustis typically interpreted as a subjective belief in the reliability， honesty and  security  of an entity on which we depend （71）our welfare .In online environments we depend on a wide spectrun of things , ranging from computer hardware,software and data to people and organizations. A security solution always assumescertain entities function according to specific policies.To trust is precisely to make this sort of assumptions , hence , a trusted entity is the same as anentity that is assumed to function according to policy . A consequence of this is that a trust component of a systemmust work correctly in order  for the security of that system to hold, meaning that when a trusted（72）fails , then the sytems and applications that depend on  it can（73）be considered secure . An often citedarticulation of this principle is:＂ a trusted system orcomponent is one that can break your security policy” ( which happens when thetrust system fails ). The same applies to a trusted party such as a serviceprovider ( SP for short )that is , it must operate according to the agreed orassumed  policy in order to ensure theexpected level of securty and quality of services . A paradoxical   conclusion to be drawn from this analysis isthat security assurance may decrease when increasing the number of trustedcomponents and parties that a service infrastructure depends on . This isbecause the security of an infrastructure consisting of many Trusted componentstypically follows the principle of the weakest link , that is ,in manysituations the the overall security can only be as strong as the least   reliable or least secure of all the trustedcomponents. We cannot avoid using trusted security  components,but the fewer the better. This isimportant to understand when designing the identity management architectures,that is, fewer the trusted parties inan identity management     model ,stronger the security that can be achieved by it .

Thetransfer of the social constructs of identity and trust into digital  and computational concepts helps in designingand implementing large scale online markets and communities,and also plays animportant role in the converging mobile and Internet environments .   Identity management (denoted Idm hereafter )is about recognizing and verifying the correctness of identitied in online environment .Trust management becomes a component of （74） whenever different parties rely on each other for identityprovision and authentication . IdM and Trust management therefore depend oneach other in complex ways because the correctness of the identity itself mustbe trusted for the quality and reliability of the corresponding entity tobe  trusted.IdM is also an essentialconcept when defining  authorisationpolicies in personalised services.

Establishing trust always has a cost , so thathaving  complex trust requirementtypically leads to high overhead in establishing the required trust . To reducecosts there will be  incentives forstakeholders to “cut corners”regarding trust requirements ,which could lead toinadequate security . The challenge is to design IdM systems with relativelysimple trust requirements. Cryptographic mechanisms are often a core componentof IdM solutions,for example,for entity and data authentication. Withcryptography,it is often possible to propagate trust from where it initiallyexists to where it is needed .The establishment of initial（75）usually takes place in the physicalworld,and the subsequent propagation of trust happens online,often in anautomated manner.

71、 A .with  B. on  C. of   D. for

72、A. entity   B. person C. component   D. thing

73、A. no longer   B. never   C. always  D. often

74、A. SP   B. IdM  C. Internet     D. entity

75、A. trust  B. cost C.  IdM    D. solution