[理工] [OS] 101 交大資工 RSA 單選
RSA 的那題:
什麼... Bob is a world-top investor (這裡英文有點小怪)
Everyone is interested in his market activity.
He buys and sells shares through his agent David, who uses RSA public key
encryption. Bob encrypts the message "PURCHASE" with David's public key
{PURCHASE}KPG and sends the encrypted message over the internet.
Bob only sends either the message "PURCHASE" or "SELL".
Who will know the contents of the message within a very short time of
acquiring {PURCHASE}KPG?
(選項順序記不得了)
A) Bob only.
B) David only.
C) Bob and David only.
D) Anybody who can acquire the message.
E) Nobody.
我的想法:
1. RSA public key 題目,只有擁有 private key 才能解密,簡單,B。
過了數秒…
等等。
2. 問題是問 "Who will know",不是 who can decrypt。Bob 有這麼蠢,蠢到自己
送了什麼都不記得嗎。 =______=
不是在開玩笑,我真的覺得誰能得知這個訊息的內容是非常重要的事。
所以是 C 囉?
正要塗答案卡…
等等!
3. 為什麼要特別提說 Bob can only send either "PURCHASE" or "SELL"?
假如說我是 attacker.... 那我得知 Bob 只會送這兩種,攔截到 cryptotext
之後的第一件事就是拿大家都隨手撿得到的 David's public key 去編碼,
然後比對出 PURCHASE 的 cryptotext 是否與我攔截到的一樣,就算不一樣
只要再試一筆就有 hit 了。所以是 D 囉?
然後就在要賭四分還是被倒扣一分半的狀況下天人交戰了許久 囧
最後選了 Anybody。
有請高手指導? 囧....
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