（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 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 C、advanced D、easy

（5）A、least B、most C、much D、less

参考答案：（1）D （2）A （3）C （4）B （5）A

参考解析：译文：

隐写术是信息隐藏的科学。密码学的目的是让数据对于第三方来说不可理解，而隐写术的目的则是让数据对于第三方来说不可见。本文讨论什么是隐写术、隐写术的用途，并举例说明。

有很多的隐写方法，其中大多数方法我们都很熟悉，尤其是对于喜欢看谍战片的人。这些方法包括隐写墨水、缩影术、将消息隐藏于大段文字中每个单词的第二个字母、无线电扩谱通信。随着计算机和网络的发展，涌现更多的方法，例如:

1.隐信道(例如Loki和某些分布式拒绝服务攻击工具使用互联网报文协议或者ICMP作为通信信道)

2.Web网页隐藏文本消息

3.“众目睽睽”之下隐藏文件(把文件隐藏在大家都熟悉的 Windows系统目录中)

4.空密码(使用每个单词的第一个字母隐藏消息)

今天的隐写术比上面提到的要更加复杂,允许用户隐藏大量的消息于图像和音频文件中。这类隐写通常与密码学一起使用以达到双重保护目的。首先它是被加密的,然后是隐藏的,对手必须首先找到消息(通常是一项艰巨任务)然后才能解密。

最简单的在图片中隐藏数据的方法是利用最低有效位。这种方法首先把数据用二进制表示然后依次覆盖图片中的每个字节的最低比特位。如果使用24比特颜色表示,那么颜色的量值变化很小,对于人眼来说几乎不可察觉。

笔记记录：

cryptography：密码学

steganography：信息隐写

sophistication ：世故; 复杂巧妙; 高水平;