Key Exchange
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This document appears to be notes from an information security course. It discusses several methods for generating and sharing secret keys securely, including using an online trusted third party, Merkle puzzles, and the Diffie-Hellman key exchange protocol. The notes cover how each method works at a high level and their advantages and disadvantages. The document focuses on generating mutual keys between two parties without needing an online trusted third party.
Key Exchange
- 1. Hoang Nguyen Van Mail: [email protected] Department of Computer Science – FITA – HUA Information Security Course --------------------------------------------- Fall 2013 Dept. of Computer Science – FITA – HUA
- 2. Information Security ------------- Fall 2013 Hoang Nguyen Van How I can share with my boyfriend, a secret key.
- 3. Information Security ------------- Fall 2013 Hoang Nguyen Van How to manage mutual keys
- 4. Information Security ------------- Fall 2013 Hoang Nguyen Van I hate my keys
- 5. Information Security ------------- Fall 2013 Hoang Nguyen Van
- 6. Information Security ------------- Fall 2013 Hoang Nguyen Van Online Trusted 3rd Party (TTP) O(n) keys per user
- 7. Information Security ------------- Fall 2013 Hoang Nguyen Van Online Trusted 3rd Party (TTP) O(1) one key per user kAB
- 8. Information Security ------------- Fall 2013 Hoang Nguyen Van Online Trusted 3rd Party (TTP) Generating keys: a toy protocol “Alice wants key with Bob” (kA) choose random kABE(kA,”AB”||kAB) ticket = E(kA,”AB”||kAB) (kB) ticket kAB kAB (Eavesdropping security only)
- 9. Information Security ------------- Fall 2013 Hoang Nguyen Van Can we generate shared keys without an online trusted 3rd party?
- 10. Information Security ------------- Fall 2013 Hoang Nguyen Van Ralph Merkle (1952)
- 11. Information Security ------------- Fall 2013 Hoang Nguyen Van Merkle Puzzles (1974)
- 12. Information Security ------------- Fall 2013 Hoang Nguyen Van Merkle Puzzles (1974) “Puzzle # xi” ll ki
- 13. Information Security ------------- Fall 2013 Hoang Nguyen Van Merkle Puzzles (1974) BobAlice puzzle1 , … , puzzlen xj kj kj O(n) O(n) O( n2 ) But Infeasible
- 14. Information Security ------------- Fall 2013 Hoang Nguyen Van The Diffie-Hellman protocol
- 15. Information Security ------------- Fall 2013 Hoang Nguyen Van 2 5 Very easy Very hard One-way function
- 16. Information Security ------------- Fall 2013 Hoang Nguyen Van 10 10 510 310 10 5 3 10 5 3 310 510 KEY Alice Bob The Diffie-Hellman protocol
- 17. Information Security ------------- Fall 2013 Hoang Nguyen Van The Diffie-Hellman protocol Alice Bob choose random a in {1,…,p-1} choose random b in {1,…,p-1} kAB = gab (mod p) = (ga) b = Ab (mod p)Ba (mod p) = (gb) a =
- 18. Information Security ------------- Fall 2013 Hoang Nguyen Van
- 19. Information Security ------------- Fall 2013 Hoang Nguyen Van