密碼學war game解答

Q1:

密碼學期中考

---

Q2: Caesar "AJY"
簡易Java程式碼如下，可線上執行：
sol: k=5 vet, k=9 rap

---

Q3:
Vigenere多套字母密文，找出金鑰長度(< 7)、金鑰、明文

Ple gkvd so hebezen bvow ple Qnieu gvyzpss, waensjk hszhex.
Ple ynmgsj sf mncpdkkrklly so ysewpli zetoz jryi ebyqx 2000
BM, smtr ple Occpdeen znecdege yb lionsgvuthsyw. Trawe
mkrssoxen kj cyitlot timpsgbwqs, ddi fehp mowrixc sf gdmcr
ses yjpy ujswx ps ax apida jeg. Ple pevsd grogj yso kj a wkhebj
gizdir gww bi Fylsqw Ckawab (100 XG ty 44 XG), wrk hin jst
dnysd dms wawsojkebo ahoj gowiynsyetsjk wspl hso kofavnynw
axz sfpegebo.

Ans:
金鑰:weak
密文:
The word is derived from the Greek kryptos, meaning  hidden. The origin of cryptography is usually dated from about 2000BC, with the Egyptian practice of hieroglyphics. These consisted of complex pictograms, the full meaning of which was only known to an elite few. The first known use of a modern cipher was by Julius Caesar (100 BC to 44 BC), who did not trust his messengers when communicating with his governors and officers

---

Q4:
這可能是哪一個password的SHA-1雜湊函數值？

1c4cb48e4fcc0769f6bdd4ba7585fad02570a371

Ans:
cracker

---

Q6:
utf-8編碼以?呈現，請轉回原漢文字串

5b6I5a655piT5ZCn77yB

Java code如下：
Ans:
很容易吧！

---

簡答題
1. SHA-1可達成密碼學四大資安功能的哪一項？
完整性。
2. 用GPG4win傳訊時，要用誰的哪一把金鑰加密？
假設Alice傳給Bob，要用Bob的公鑰。
3. 人類已經發明了完美無法破解的密碼？如果有，叫什麼？
單次密碼簿(One-Time Pad)
4. RSA的安全性，是假設在什麼難題之上？
質因數分解的困難度。
5. 請使用GPG4win找尋你的某一位朋友的帳號，並將其設定為”marginal trust”