关于加密技术，下列________是错误的。
A．对称密码体制中加密算法和解密算法是保密的
B．密码分析的目的就是千方百计地寻找密钥或明文
C．对称密码体制的加密密钥和解密密钥是相同的
D．所有的密钥都有生存周期
参考答案：A
解析：[知识点] 加密与认证技术
[评析] 对称密码体制是一种传统密码体制，也称为私钥密码体制。在对称加密系统中，加密和解密采用相同的密钥。因为加解密密钥相同，需要通信的双方必须选择和保存他们共同的密钥，各方必须信任对方不会将密钥泄密出去，这样就可以实现数据的机密性和完整性。由此看出，对称密码体制中加密算法和解密算法并不是保密的。
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| People all over the world enjoy sports. Sports are good for people's health and sports make people 1 . Some people like to play games by themselves, but some enjoy watching others 2 sports games. They buy tickets or turn on their TV to watch games. They usually have "their teams" or "their players". When "their teams" can't win the game, they are even 3 than the players themselves. Sports change with the 4 . People play different games in different seasons. Most people's favorite sport 5 summer is swimming and skating is usually a winter sport. Sometimes people play games inside the room, sometimes they play outside. We can 6 sports here and there. Some sports are very interesting and people 7 like them. Football, for example, is very 8 in the world. Men and women, the old and the young all like it. People from different countries 9 understand each other, but after a game they often become 10 . | |||
| ( )1. A. happy ( )2. A. play ( )3. A. busier ( )4. A. time ( )5. A. to ( )6. A. look ( )7. A. may ( )8. A. great ( )9. A. can not ( )10.A. same player | B. strong B. to play B. angrier B. seasons B. for B. find B. are B. favorite B. can B. better players | C. interesting C. plays C. worse C. countries C. in C. talk C. nowhere C. popular C. may C. good friends | D. tired D. played D. sadder D. people D. in the D. watch D. everywhere D. well D. must D. different players |