In a public-key cryptosystem, (71) encrypted with the public key can only be deciphered with the private key from the same (72) . Conversely, (71) encrypted with the private key can be decrypted only with the public key. Users can make their public keys (73) available or place them at a key distribution center or others to access. However, the private key must be (74) safe. In public-key systems there’s no (75) to find a safe channel for communicating a shared secret key.

A. binarytext B. hypertext C. plaintext D. supertext

信息系统是由这样一些学科相互渗透而发展起来的一门边缘性学科，这些学科是 ( )。

A．信息科学、计算机科学、系统科学、管理科学、决策科学、知识工程、智能工程

B．信息科学、系统科学、管理科学

C．信息科学、计算机科学、系统科学、管理科学

D．信息科学、计算机科学、系统科学、管理科学、决策科学