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# 多媒體檔案安全傳輸與設計 - PowerPoint PPT Presentation

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## 多媒體檔案安全傳輸與設計

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### 多媒體檔案安全傳輸與設計

• 團隊資料
• 研發成果說明
• 金鑰交換流程
• 數據分析
• 安全性驗證

• 以傳送影音檔為題材，實作金鑰交換
• 開發之程式語言為Java
• 改進Diffie-Hellman演算法
Diffie-Hellman

B

A

Xb =g mod p

b

Xa =g mod p

a

Ka = (Xb) mod p

a

Kb = (Xa) mod p

b

Kb = g mod p

ab

Ka = g mod p

ba

C

Xa??

Xb??

Diffie-Hellman

B

A

Xb =g mod p

b

Xa =g mod p

a

Ka = (Xc) mod p

a

Kb = (Xc) mod p

b

Kb = g mod p

cb

Ka = g mod p

ca

C

Xc =g mod p

c

c

c

Ka = (Xa) mod p

Kb = (Xb) mod p

Ka = g mod p

ac

Kb = g mod p

bc

A

B

Xa⊕h(Q)

Xb =g mod p

b

Xa =g mod p

a

Xb⊕h(Q)

Xa = Xa⊕h(Q)

Xb = Xb⊕h(Q)

Kb = (Xa) mod p

b

Ka = (Xb) mod p

a

Kb = g mod p

ab

Ka = g mod p

ab

h(IDa, Q, Ka)

h(IDa, Q, Kb)

Compare

h(IDb, Q, Ka)

h(IDb, Q, Kb)

Chang的方法

A

B

Xa⊕h(Q)

Xb =g mod p

b

Xa =g mod p

a

Xb⊕h(Q)

Xa = Xa⊕h(Q)

Xb = Xb⊕h(Q)

Kb = (Xa) mod p

b

Ka = (Xb) mod p

a

Kb = g mod p

ab

Ka = g mod p

ab

M1 = E[Xa, r]Ka

D[M1]Kb = Xa, r

Check Xa == Xa (D[M1]Kb)

Kb is authencated

D[r]Ka = r

M2 = E[r]Kb

Check r == r

Ka is authencated

Chang的方法

• 密碼攻擊(Password guessing attack)
• 連線密碼攻擊：窮舉法攻擊是無法達成目的
• 離線密碼攻擊：雜湊函數無法逆運算
• 重送攻擊(Replay attack)
• 無法通過認證機制

• 中間人攻擊(Man-in-the-middle attack )
• 利用Q值保護訊息安全
• 認證機制確保接收方身分
• 完整性順向機密(Perfect forward secrecy)
• 每次會議金鑰與之前或之後的任何金鑰都沒有任何關連

[1] C. C. Chang and S. Y. Lin, “An Improvement on Authenticated Key Agreement Scheme,” Intelligent Pervasive Computing, 2007.

[2] W. Diffe and M. Hellman, “New directions in cryptography,” IEEE Transactions on Information Theory, Vol. 22, pp. 644-654, 1976.

[3] L. Gong, “Optimal authentication protocols resistant to password guessing attacks,” Proceedings of the Eighth IEEE Computer Security Foundations Workshop, Country Kerry, Ireland, pp. 24-29,1995.

[4] K. J. Lee and B. J. Lee, “Cryptanalysis of the modified authenticated key agreement scheme,” Applied Mathematics and Computation, Vol.170, pp.280-284, 2005.

[5] Bruce Schneier, “Applied Cryptography,” John Wiley & Sons, Inc., 1996.