题目内容

阅读下列说明和图，回答问题1至问题4，将解答填入答题纸的对应栏内。
[说明]
某公司计划与客户通过Internet交换电子邮件和数据(以下统一称为“消息”)。为保障安全，在对传输的数据进行加密的同时，还要对参与通信的实体进行身份认证。因此，需同时使用对称与非对称密钥体系。图3-1描述了接收者B使用非对称密钥体系对发送者A进行认证的过程。
[图3-1]
图3-2描述了发送和接收消息的过程，其中的认证过程使用了图3-1中的方法。图3—1中的方框a和方框b与图3-2中的方框a和方框b相同。
[图3-2]
图3-2中发送和接收消息的过程是：
1)发送者A使用与接收者B共享的对称密钥体系的密钥加密将要发送的消息。
2)为了实现身份认证，A使用与B共享的摘要算法生成消息摘要，并使用公钥密码体系把生成的消息摘要加密后发送给B(这里假设A和B都能通过安全的方法获得对方的公钥)。
3)B使用非对称密钥体系解密收到的消息摘要，使用与A共享的对称密钥体系的密钥解密加密后的消息，再使用与A共享的摘要算法针对解密后的消息生成消息摘要。
4)B对比自己生成的消息摘要与接收到的A发送的消息摘要是否相同，从而验证发送者A的身份。
请在下列选项中选择合适的答案，填入图3-1、图3-2的方框a和方框b。
B的公钥，B的私钥，摘要算法，A的私钥，A的公钥，会话密钥

查看答案

搜索结果不匹配？点我反馈

更多问题

按照图3-2中的方法发送邮件时，使用不同的密码体制加密消息和消息摘要，请用 150字以内文字简要说明这样做的理由。

阅读以下说明和C代码，将应填入(n)处。
[说明]
在一公文处理系统中，开发者定义了一个公文结构OfficeDoc，其中定义了公文应该具有的属性(字段)。当公文的内容或状态发生变化时，与之相关联的DocExplorer结构的值都需要发生改变。一个OfficeDoc结构能够关联一组DocExplorer结构。当OfficeDoc结构的内容或状态发生变化时，所有与之相关联的DocExplorer结构都将被更新，这种应用被称为观察者模式。以下代码采用C语言实现，能够正确编译通过。
[C代码]
include ＜stdio.h＞
define OBS_MAXNUM 20 /一个OfficeDoc变量最多能够关联的/
/DoeExplorer变量的个数/
typedef void((1))(struct OfficeDoc,street DocExplorer);
struct DocExplorer{
func update;/* DocExplorer结构采用的更新函数/
/其他的结构字段省略/
};
struct OfficeDoc{
(2) myObs[OBS_MAXNUM];
/存储所有与OfficeDoc相关联的DoeExplorer结构指针/
int index;/与OfficeDoc结构变量相关联的DocExplorer结构变量的个数/
};
void attach(struet OfficeDoc doc, struet DocExplorer ob){
/关联Obersver结构ob与OfficeDoe结构doc/
int loop=0;
if(doc-＞index ＞=OBS_MAXNUM || b==NULL) return;
for(loop=0; loop ＜doc-＞index; loop++)
if(doc-＞myObs[loop]==ob)return;
doc-＞myObs[doe-＞index]=ob;
doc-＞index++;
)
void detach(struct OfficeDoc doc, struct DocExplorer ob){
/解除doc结构与ob结构间的关系/
int loop;
if(ob==NULL)return;
for(loop=0; loop ＜doc-＞index; loop6++){
if(doc-＞myObs[loop]==ob){
if(loop＜=doc-＞index-2)
doe-＞myObs[loop]=doc-＞myObs[ (3) ];
doc-＞myObs[doe-＞indox-1]=NULL;
doe-＞index--;
break;
}
}
}
void updatel(struct OfficeDoc doc,struct DocExplorer ob){
/更新ob结构的值，更新代码省略/
}
void update2(stmct OfficeDoc doc, struct DocExplorer ob){
/更新ob结构的值，更新代码省略/
}
void notifyObs(struet OfficeDoc doc){
/当doc结构的值发生变化时，通知与之关联的所有DocExplorer结构变量/
int loop;
for(loop=0; loop ＜doc-＞index; loop++){
(doc-＞myObs[loop])-＞update((4));
}
}
void main(){
stmct OfficeDoc doc;/定义一OfficeDoc变量/
struct DocExplorer explorer1, explorer2;/定义两个DocExplorer变量/
/初始化与OfficeDoc变量相关的DocExplorer变量个数为0/
doc.index=0;
explorer1.update=update1;/设置explorer1变量的更新函数/
explorer2.update=update2;/设置explorer2变量的更新函数/
attaeh(&doc,&explorer1);/关联explorer1与doc对象/
attach(&doc,&explorer2);/关联explorer2与doc对象/
/其他代码省略/
(5);/通知与OfficeDoc相关的所有DocExplorer变量/
return;
}

SECTION B ENGLISH TO CHINESE
Directions: Translate the following text into Chinese.
Advice for Families from the Scottish Council for Research in Education.
"If you are worried discuss this with a teacher."
Bullying is not easy to define. Sometimes it involves hitting or kicking. But threats, teasing, and taunting are more common and can be more damaging. The word "bullying" is used to describe many different Woes of behaviour ranging from teasing or deliberately leaving an individual out of a social gathering or deliberately leaving un individual out of a social gathering or ignoring them, to serious assaults and abuse. Sometimes it is an individual who is doing the bullying and sometimes it is a group.
The important thing is not the action but the effect on the victim. No one should ever underestimate the fear that a bullied child feels.
This advice sums up the most important actions to take:
If someone in your family is being bullied at school, you have to do something to help. You must talk to a teacher.
If you are worried that someone in your family may be bullied -- discuss this with a teacher.
If you want to help rid schools of bullying -- work with the teachers to make school safer and happier.
If you are not satisfied with the school's response, do not give up -- other sources of help are available.
Support and understanding at home are important in helping people to cope with bullying -- families should do all they can to help children and young people value themselves.
Children and young people who witness or become aware of bullying may be unsure what to do and whether they should tell someone. Make sure they know that they should talk to a parent or teacher, and why.
The KEY MESSAGES to get across to the person being bullied are:
It's not your, fault that you are being bullied.
You don't have to face this on your own.

Writing a short composition of about 250 to 300 words on the topic given below. (15%)
Topic: Write in 250 ～ 300 words about your own academic ambition(s)