问题 单项选择题

以下关于公钥密码体制的描述中,错误的是______。

A.加密和解密使用不同的密钥

B.公钥不需要保密

C.一定比常规加密更安全

D.常用于数字签名、认证等方面

答案

参考答案:C

解析:[知识点] 网络安全技术[评析] 认为公钥加密比常规加密更具有安全性的概念是错误的。实际上,任何加密方案的安全性都依赖于密钥的长度和解密所需的计算工作量。从防止密码分析的角度来看,常规加密和公钥加密并没有任何一点能使其中一个比另一个优越。

阅读理解

Which animal do you think is "the king of the animals", the elephant, the lion or the tiger? They are all large and strong. But I think the tiger is "the king of the animals". If you watch carefully, you can find some black lines on the tiger's forehead(前额). The lines look like the Chinese word "WANG". The word means "the king of the world" in Chinese.

Most of the tigers come from China and India. Tigers are dangerous animals. They look scary(吓人的). They like eating meat. They have yellow fur with black lines. They usually weigh about 200 to 300kg. Tigers can run fast. They run at a speed of 20 meters per second.

Some people think they are dangerous. But they don't know tigers are in danger now. There are only 20 to 30 wild South China Tigers in China and less than 300 in the world. Lots of people kill them for their fur. We should take action to protect them.

小题1:Which animal does the writer think is "the king of the animals" ?

A.The elephant.

B.The lion.

C.The tiger.

D.The lion and the tiger.小题2:Some black lines on the tiger's forehead look like ___________.

A.王

B.汪

C.主

D.丰小题3:Which of the following is NOT true according to the passage?

A.Tigers like eating meat.

B.All of the tigers come from China.

C.Tigers usually weigh about 200 to 300 kg.

D.Tigers can run at a speed of 20 meters per second.小题4:How many wild South China Tigers are there in China?

A.There are less than 20.

B.There are only 20 to 30.

C.There are less than 200.

D.There are less than 300.小题5:Why do you think the tigers are in danger?

A.Because the tigers couldn't find enough food to eat.

B.Because lots of people kill them for their safety.

C.Because lots of people think they are dangerous.

D.Because lots of people kill them for their fur.

单项选择题