问题 问答题 简答题

什么是数据完整性?说明数据完整性鉴别机制的基本原理。

答案

参考答案:

数据完整性是指数据的正确性、有效性和相容性。

数据完整性鉴别的基本原理

1.消息的发送者将消息(即发送的信息)用数学算法H生成一个附件(称为原附件),并将原附件与消息一并发送出去;

2.消息的接收者收到消息和附件后,用同样的算法H对接收到的消息生成一个新附件,并把新附件与接收到的原附件相比较:如果相同,则说明收到的消息是正确的,否则说明消息在传送中出现了错误。

阅读理解

阅读下面的短文,根据短文内容回答问题。

     New rules and behaviour standards (行为规范) for middle school students came out (颁布) in March.

Middle schools are going to use a new way to decide who the top students are. The best students won't

only have high marks. The following are some of the new rules.

     Tell the truth. Have you ever cheated (作弊) in an exam? Don't do it again! That's not something honest

students should do.

     Do more at school. Good students love animals and care for other people. April is Bird loving Month in

China. Is your school doing anything to celebrate it? You should join! In that way, you can learn more about

animals and how to protect (保护) them.

     Be open to new ideas. Have you ever thought people could live on the moon? Maybe you'll find another

earth in space in the future. Everyone's new ideas are important.

     Protect yourself. Has a thief ever taken money from one of your classmates? Don't let it happen to you.

If you have to go back home late, you should let your parents know.

     Use the Internet carefully. The Internet can be very useful for your study. But some things on the Internet

aren't for kids, so try to look at the good web pages (网页). You can use the web pages for fun or homework.

1. What should the best students do in an exam?

                                                                                                                 

2. What should you do if you have to go back home late? 

                                                                                                                    

3. What can the children use the good web pages for? 

                                                                                                                    

4. When did the new rules come out? 

                                                                                                                    

5. Which new idea do you think may come true? 

                                                                                                                    

问答题