问题 单项选择题

(29) 技术的使用,使数据信息在公共网络中的传输有了安全保障。

A.数据加密

B.数字信封

C.CA认证

D.数字签名

答案

参考答案:B

解析:[分析]
本题考查网络安全的一些技术。
(1)数据加密是对明文按照某种加密算法进行处理后形成密文。
(2)数字信封是数据加密技术的一种应用。在数字信封中,信息发送方采用对称密钥来加密信息内容,然后将此对称密钥用接收方的公开密钥来加密(这部分称数字信封)之后,将它和加密后的信息一起发送给接收方,接收方先用相应的私有密钥打开数字信封,得到对称密钥,然后使用对称密钥解开加密信息。这种技术的安全性相当高。
(3)CA认证是指对用户证书的鉴别。
(4)数字签名用来保证信息传输过程中信息的完整,以及提供信息发送者的身份认证和不可抵赖性。

阅读理解

阅读理解。

     Once there lived a very exact(精确的) man. One day when he was walking in the street, an old woman came over and asked him," Excuse me, where is the nearest restaurant?"

     "The nearest restaurant? You have to cross the bridge and then turn to the right," answered the man.

     "And is the bridge long?"

     "Very long, thirty meters."

     The old woman thanked him and went towards the bridge. Suddenly she heard someone running after her. "Stop ! " the man was shouting. "I'm very sorry. I just remembered: the bridge is forty meters long. If you go thirty meters and then turn to the right, as I told you to do, you'll fall into the river. "

1. What was the man doing one day?

A. He was thinking about an interesting problem.

B. He was doing some running in the park.

C. He was on his way to see a film.

D. He was walking in the street.

2. The old woman wanted _________.

A. to buy a coat in a shop

B. to go to the nearest restaurant

C. to take a walk

D. to go to the nearest theatre

3. The man first told her the bridge was _________.

A. half a kilometer

B. forty meters long

C. thirty meters long

D. twenty minutes' walk

4. Why was the man running after the old woman? Because _________.

A. he just remembered the real length (长度) of the bridge

B. he knew her name

C. he didn't tell her the way to the restaurant

D. he wanted to catch her

5. If he didn't stop her, the woman would _________.

A. lose her way

B. fall into the river

C. be angry with him

D. also find the restaurant

单项选择题