英语翻译In Julius Caesar’s Gallic Wars,he describes how he sent

英语翻译
In Julius Caesar’s Gallic Wars,he describes how he sent a message to the
besieged Cicero.The messsage was encrypted by substituting Greek letters for
Roman letters,then delivered in the most dramatic way imaginable.The
messenger,unable to reach the camp,hurled a spear with the letter fastened to
it with a thong.Although the spear lodged itself in a tower,nobody spotted it
for two days.Eventually,it was taken down and delivered to Cicero,who read
out the vital news to the entire camp,bringing enormous joy to his troops.
This was the first documented use of a substitution cipher for military
purposes.Substitution ciphers,as the name suggests,encrypt messages by
replacing the original characters with different characters.This is in contrast
to a transposition cipher,in which the characters remain the same,but they
are transposed or rearranged to create an anagram.
One of the most famous substitution ciphers is the so-called Caesar cipher,
which simply replaces each letter in the message with the letter that is,say,
three places further down the alphabet.Cryptographers often think in terms
of the plain alphabet,the alphabet used to write the original message,and the
cipher alphabet,the letters that are substituted in place of the plain letters,
both of which are shown below.
……
The plaintext is the technical name for the original message,while the
ciphertext is the encrypted message.In this chapter,the plaintext is written in
lower case and the ciphertext in upper case.Although this example involves a
shift of 3,lesser or greater shifts are of course possible.The Caesar cipher can
be generally stated as substituting each plain letter with the letter that is x
places later in the alphabet,where x is between 1 and 25.This illustrates one
of the basic principles of cryptography,namely the relationship between the
algorithm and the key.
In the Caesar cipher,the algorithm is the general idea of replacing the
original letters with those that lie a fixed number of places further along the
alphabet.The key,x,specifies the distance of the shift.In other words,the key
is a flexible component within the algorithm,which needs to be specified in
order to determine the exact method of encryption.The key is usually
selected by the sender and has to be communicated to the receiver so that the
message can be deciphered.
A codebreaker can crack the cipher by identifying the correct key.In this
case,the codebreaker can check every key,known as a brute force attack,
because there are only 25 keys.

在凯撒的高卢战争中,他描述他是如何发出了一个信息,
西塞罗围困.被加密的messsage代希腊字母
罗马字母,然后交付最戏剧性的方式可想而知.该
信使,无法达到营地,投掷一个固定在信矛
它与一通.虽然提出了塔本身的矛,没有人发现它
两天.最终,它被取下来,并送交西塞罗,谁读
出的重要消息,整个营地,带来了巨大的欢乐,他的部队.
这是首次有记载的一替换密码用于军事
目的.替代密码,顾名思义,通过加密邮件
不同的字符替换原来的字符.这是相
一个换位密码,其中的人物保持不变,但他们
被调换或重新安排,以创建一个字谜.
其中最有名的替代密码之一是所谓的凯撒密码,
它只是以字母代替,即在邮件中说,每一个字母,
粤港澳三地进一步下跌字母表.密码学家通常认为的术语
平原字母,字母用来书写的原始信息,并且
密码字母,认为是在平原字母取代字母的地方,
这两者都是所示.
......
明文是为原始信息技术的名称,而
密文是加密的信息.在这一章中,明文写在
小写和大写的密文.虽然这个例子涉及一个
转移3,或多或少的变化是不可能的.凯撒密码可以
普遍表示为代以字母是每一个普通的字母X
在字母表中,其中x是介于1和25后的地方.这说明了一个
对密码学的基本原则,即之间的关系
算法和密钥.
在凯撒密码,该算法是更换的总体思路
与那些撒谎的地方沿固定数量的进一步原始信件
字母表.关键,x,指定移位距离.换句话说,关键
是一个在算法,这需要灵活的组件中指定
为了确定确切的加密方法.关键是通常
选定的发送者和要传达给接收器,使
消息可以被破译.
可以破解一个密码破译通过确定正确的密钥的密码.在这
情况下,密码破译者可以检查每一个关键,这是已知的强力攻击,
因为只有25个键.