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问题 多项选择题

数字签名具体做法是（）

A.将报文按双方约定的HASH算法计算得到一个固定位数的报文摘要

B.将报文摘要值用发送者私有密钥加密

C.接收方用HASH算法对报文计算摘要值

D.接收方用发送者的私有密钥对报文摘要进行解密

答案

参考答案：A, B, C

单项选择题

烟气密度随（）而减小。

A、温度的升高和压力的降低

B、温度的降低和压力的升高

C、温度的升高和压力的升高

D、温度的降低和压力的降低
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单项选择题

Nasreddin had a shed(棚子)behind his house. It had no lights in it. One night he went out to the shed to get his ladders(梯子)and lost his ring(戒指)there. He left the ladder, went out into the street and began to look around.
One of his friends saw him in the street outside his house, and said to him, " Hello, Nasreddin, what are you looking for"
"My ring , "answered Nasreddin. "It fell off my finger. It is a silver(银的)ring with a red stone in it." "Oh, yes. "said the friend. "I remember it. I will help you to look for it. Where did you lose it"
"In my shed."
"But why don’t you look for it there"
"Don’t be foolish! It is quite dark in my shed, how can I find my ring there Here there is light from the lamps in the street.\

Nasreddin thought he could find his ring because ______.
A. his friend would help him
B. it was dark in the shed
C. it was bright outside
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