: ※ 引述《wakke (衝阿 去掉C)》之銘言： : 列舉兩題 : 43. When using public key encryption scheme, : how to let A securely transmit a message to B, : and let B believe that the message is indeed sent by A？ : (A) use A’s public key to encrypt the message, : and then use B’s private key to encrypt the previous encrypted message : (B) use A’s private key to encrypt the message, : and then use B’s public key to encrypt the previous encrypted message : (C) use B’s public key to encrypt the message, : and then use A’s private key to encrypt the previous encrypted message : (D) use B’s private key to encrypt the message, : and then use A’s public key to encrypt the previous encrypted message : (E) none of the above http://0rz.net/350nJ 因為 public/privite key 都是一組 key，都可以用來加解密 只是用一個加密，就要用另一個解密 一般 public key 都是讓別人可以取得的 所以加密用對方的 public key 加密 對方收到後就可以用他自己的 private key 解密 而要確定是A傳的(這叫做A對他的信簽名) A用他自己的 private key 加密，附在信的後面 別人收到後就用 A 的 public key 解密 如果解出來一樣，救代表這的確是 A 傳的 所以答案是 B，先簽名，然後加密 我想 C 是因為簽名的訊息留在外面，比較不安全吧(不太確定...) : 31. Which of the following is wrong？ : (A) public key encryption is also called asymmetric key encryption : because the encryption and decryption use different keys : (B) private key encryption is also called symmetric key encryption : because the encryption and decryption use the same keys : (C) public key encryption scheme can be used for digital signature : (D) PGP is used to secure email messages : (E) all of the above are correct http://en.wikipedia.org/wiki/Asymmetric_key_algorithm symmetric 是說加/解密用同一組 key assymmetric 是用不同 key 所以是(B) --

※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.113.122.140 ※ 編輯: ccpz 來自: 140.113.122.140 (05/31 19:56)