推 deepdish:翻了一下電腦網路-網路安全的部分 應該都說對了 140.115.201.17 05/31
※ 編輯: ccpz 來自: 140.113.122.140 (05/31 19:56)
→ wakke:THX :)140.113.123.246 05/31
: ※ 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)
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