There are two types of key technology：private key and public key.Private-key encryption methods are called(1)ciphers，information is encrypted with(2)both the sender and receiver hold privately.Public—key encryption methods are called(3)ciphers，(4)created for each user，encryption key and decryption key are(5).
(1)A.synchronous
B.asynchronous
C.symmetric
D.asymmetric
(2)A.a key
B.two keys
C.three keys
D.four keys
(3)A.synchronous
B.asynchronous
C.symmetric
D.asymmetric
(4)A.two related keys are
B.a key is
C.two unrelated keys are
D.three keys are
(5)A.same
B.different
C.difference
D.some
答案：(1)C (2)A (3)D (4)A (5)B
解析：有兩種加密技術(shù)：私有密鑰和公開密鑰。私有密鑰加密方法被稱為對(duì)稱密鑰加密，在發(fā)送者和接受者之間的信息共同具有同一個(gè)密鑰，公開密鑰加密方法被稱為非對(duì)稱密鑰加密，對(duì)于每一個(gè)使用者，都建立兩個(gè)相關(guān)的加密與解密密鑰，但它們不同。