问题 单项选择题

RSA是一种公开密钥加密算法。其原理是:已知素数p、q,计算n=pq,选取加密密钥e,使e与(p-1)×(q-1)互质,计算解密密钥d= e-1mod((p-1)×(q-1))。其中n、e是公开的。如果M、C分别是明文和加密后的密文,则加密的过程可表示为(51)。假定Eyx表示利用x的密钥Y对消息M进行加密,Dyx表示利用x的密钥Y对消息M进行解密,其中Y=P表示公钥,Y=S表示私钥。A利用RSA进行数字签名的过程可以表示为(52),A利用RSA实施数字签名后不能抵赖的原因是(53)。

空白处(51)应选择 ()

A.C=Memodn 

B.C=Mnmode 

C.C=Mdmodn 

D.C=Memodd

答案

参考答案:A

解析:

本题考查RSA的基本知识。RSA的原理如题所述,加密过程是先将明文分成多个组,每组看成一个整数M,加密就是计算C=Mmodn。RSA可以用于数字签名,其过程是:用签名者的私钥对消息加密,然后再用接收者的公钥对加密后的内容加密。因为签名过程中用签名者的私钥对消息进行了加密,且只有签名者本人知道其私钥,因此这样的签名是不能抵赖的。

阅读理解

In 1901,H. G. Wells, an English writer, wrote a book describing a trip to the moon. When the explorers landed on the moon, they discovered that the moon was full of underground cities. They expressed their surprise to the “moon people” they met. In turn, the “moon people” expressed their surprise. “Why,” they asked, “are you traveling to outer space when you don’t even use your inner space?”

H.G. Wells could only imagine travel to the moon. In 1969, human beings really did land on the moon. People today know that there are no underground cities on the moon. However, the question that the “moon people” asked is still an interesting one. A growing number of scientists are seriously thinking about it.

Underground systems are already in place. Many cities have underground car parks. In some cities, such as Tokyo, Seoul and Montreal, there are large underground shopping areas. The “Channel”,a tunnel connecting England and France, is now complete.

But what about underground cities? Japan’s Taisei Corporation is designing a network of underground systems, called “Alice Cities”. The designers imagine using surface space for public parks and using underground space for flats, offices, shopping, and so on. A solar dome would cover the whole city.

Supporters of underground development say that building down rather than building up is a good way to use the earth’s space. The space, they say, can be used for farms, parks, gardens, and wilderness. H.G. Wells “moon people” would agree. Would you?

小题1:The explorers in H.G. Well’s story were surprised to find that the “moon people”      .

A.knew so much about the earth

B.understood their language

C.lived in so many underground cities

D.were ahead of them in space technology小题2:What sorts of underground system are already here with us?

A.Offices, shopping areas, power stations

B.Tunnels, car parks, shopping areas

C.Gardens, car parks, power stations

D.Tunnels, gardens, offices小题3:What would be the best title for the text?

A.Alice Cities—cities of the future

B.Space travel with H.G. Wells

C.Enjoy living underground

D.Building down, not up

单项选择题