第17题:[单选题] How long should the volunteer serve during the school year? (A) A. At least one fully day during the school year. B. At best one and a half day during the school year. C. One week during the school year. D. The whole school year. 参考答案:A
为了检验数字证书的合法性,要使用( )来验证。 A. 颁发者的公用密钥 B. 颁发者的私有密钥 C. 使用者的公用密钥 D. 使用者的私有密钥 参考答案:A 答案解析:[解析] 为了保证使用者公用密钥的完整性,需要使用由某一证书权威机构颁发的数字证书来分发公用密钥。为了证明数字证书的合法性,证书必须经该权威机构进行数字签名。当用户使用证书时,用该机构的公用密钥来检查