问题 单项选择题

计算机采用单向函数来保证登录口令的安全性,此时在计算机内()

A.只存储登录口令

B.只存储登录口令的单向函数值

C.只存储单向函数算法

D.不存储和口令相关的任何值

答案

参考答案:B

解析:

本题考查单向函数的基础知识。

计算机登录口令的管理方式非常重要。如果用户的口令都存储在一个文件中,那么一旦这个文件暴露,非法用户就可获得口令。目前,计算机采用单向函数来解决口令管理问题,即计算机并不存储直接口令,只存储口令的单项函数。其识别过程如下:

①用户将口令传送给计算机;

②计算机完成口令单向函数值的计算;

③计算机把单向函数值和机器存储的值比较。

这样非法侵入者想获得合法用户口令就不会太容易了。

阅读理解

阅读短文,选择正确答案。

     The Niagara Falls is between Canada and the United States in the east central North America. It's on a river

that connects two of the five Great Lakes. The Niagara Falls has two parts: the Horseshoe Falls on the Canadian

side of the river, and the American Falls on the United States' side. They are about 50 meters high ,1240 meters

wide.

     The Niagara Falls has three special falls. The tallest are the American and Bridal Veil falls on the American

side. The falls are colorfully lit up at night, and many people say they're even more beautiful in winter, when the

grounds are covered with snow and the waters turn to ice.

     Most visitors go as close to the falls as possible, and watch the waters thundering down. The Niagara Falls is

different from the waterfalls you find in mountains, where a thin stream of water comes down a mountainside,

half-flying.

     Above in the air, you will understand the real difference between the American and Canadian Falls. The

American Falls get only about 10% of the water, while the Canadian Falls get 90%.

1. The Niagara Falls is about ______. [ ]

A. 50 meters wide

B. 1240 meters high

C. 1240 meters long

D. 50 meters high

2. It's said that the Niagara Falls is even more beautiful in _______. [ ]

A. winter

B. summer

C. autumn

D. spring

3. The word "stream" means _______ in Chinese. [ ]

A. 大海

B. 溪流

C. 湖泊

D. 绿洲

4. Which of the following is NOT true? [ ]

A. The Niagara Falls in in North America.

B. The Niagara Falls has two parts.

C. The American Falls get most water.

D. The Niagara Falls is very beautiful.

解答题