Содержание
- 2. Chapter 6 Other Security Building Blocks Motivation for Secret Splitting A professor, Carol, encrypts her
- 3. Chapter 6 Other Security Building Blocks Secret Splitting Secret splitting makes it possible to divide
- 4. Chapter 6 Other Security Building Blocks Secret Splitting Using One-Time Pads M = “THEKEYISTHREE” Create
- 5. Chapter 6 Other Security Building Blocks Secret Split. with One-Time Pads Encrypt C1 with P2:
- 6. Chapter 6 Other Security Building Blocks Secret Sharing Secret sharing (also called a threshold scheme)
- 7. Chapter 6 Other Security Building Blocks Motivation for Blind Sig’s Dave owns a bank Carol
- 8. Chapter 6 Other Security Building Blocks Blind Signatures Blind signatures enable a user to digitally
- 9. Chapter 6 Other Security Building Blocks Blind Signatures (cont) Carol blinds the message: B =
- 10. Chapter 6 Other Security Building Blocks Blind Signatures (cont) Dave signs the blinded message as
- 11. Chapter 6 Other Security Building Blocks Blind Signatures (cont) Carol unblinds the signed blinded message
- 12. Chapter 6 Other Security Building Blocks Properties of Blind Signatures Validity – as with normal
- 13. Chapter 6 Other Security Building Blocks Unlinkability of Blind Signatures Suppose: Carol gives Dave two
- 14. Chapter 6 Other Security Building Blocks Example of Unlinkability Carol gives Dave two blinded documents
- 15. Chapter 6 Other Security Building Blocks Example of Unlinkability (cont) To link an unblinded document
- 16. Chapter 6 Other Security Building Blocks Motivation for Blind Signatures (cont) Why would Dave sign
- 17. Chapter 6 Other Security Building Blocks Digital Money Without Blind Sig’s Carol creates a message
- 18. Chapter 6 Other Security Building Blocks Digital Money With Blind Signatures Carol creates a message
- 19. Chapter 6 Other Security Building Blocks Digital Money With Blind Signatures (cont) Problem #1: double
- 20. Chapter 6 Other Security Building Blocks Digital Money With Blind Signatures (cont) Problem #2: fraud
- 21. Chapter 6 Other Security Building Blocks Digital Money With Blind Signatures (cont) Dave requires Carol
- 22. Chapter 6 Other Security Building Blocks Digital Money With Blind Signatures (cont) Dave chooses 99
- 23. Chapter 6 Other Security Building Blocks Digital Money With Blind Signatures (cont) For Carol to
- 24. Chapter 6 Other Security Building Blocks Motivation for Bit Commitment Might want to commit to
- 25. Chapter 6 Other Security Building Blocks Motivation for Bit Commitment (cont) Chuck and Bill’s virtual
- 26. Chapter 6 Other Security Building Blocks Bit Commitment Bit commitment allows someone to commit to
- 27. Chapter 6 Other Security Building Blocks Bit Commitment Using a Symmetric-Key Cryptosystem Commitment phase: Chuck
- 28. Chapter 6 Other Security Building Blocks Bit Commitment Using a Symmetric-Key Cryptosystem Commitment phase: Bill
- 29. Chapter 6 Other Security Building Blocks Bit Commitment Using a Symmetric-Key Cryptosystem Neither can cheat:
- 30. Chapter 6 Other Security Building Blocks Bit Commitment Using a One-Way Hash Function Commitment phase:
- 31. Chapter 6 Other Security Building Blocks Bit Commitment Using a One-Way Hash Function Neither can
- 32. Chapter 6 Other Security Building Blocks Cryptographic Protocols A protocol is an agreed-upon sequence of
- 33. Chapter 6 Other Security Building Blocks Key Exchange with Symmetric Cryptography Assume Alice and Bob
- 34. Chapter 6 Other Security Building Blocks Key Exchange with Symmetric Cryptography (cont) Agreeing on a
- 35. Chapter 6 Other Security Building Blocks Key Exchange with Symmetric Cryptography (cont) The key-exchange protocol:
- 36. Chapter 6 Other Security Building Blocks Key Exchange with Symmetric Cryptography (cont) Issues: Security depends
- 37. Chapter 6 Other Security Building Blocks Attacking the Protocol Alice and Bob set up a
- 38. Chapter 6 Other Security Building Blocks Attacking the Protocol (cont) A: => KDC (A,B); KDC:
- 39. Chapter 6 Other Security Building Blocks What Went Wrong? Alice and Bob need to be
- 40. Chapter 6 Other Security Building Blocks Using Timestamps to Establish Freshness A: => KDC (A,B);
- 41. Chapter 6 Other Security Building Blocks Using Nonces to Establish Freshness A nonce is a
- 42. Chapter 6 Other Security Building Blocks Key-Exchange with Public-Key Cryptography Alice learns Bob’s public key
- 43. Chapter 6 Other Security Building Blocks Attacking the Protocol Recall the man-in-the-middle attack If Mallory
- 44. Chapter 6 Other Security Building Blocks The Interlock Protocol Combating the man-in-the-middle attack: Alice and
- 45. Chapter 6 Other Security Building Blocks The Interlock Prot. (cont) Foiling the man-in-the-middle: Assume Mallory
- 46. Chapter 6 Other Security Building Blocks Authentication Authentication is the process of proving your identity
- 47. Chapter 6 Other Security Building Blocks One-way Authentication Using Symmetric-Key Cryptography Assume that Alice and
- 48. Chapter 6 Other Security Building Blocks One-way Authentication Using Symmetric-Key Cryptography Problem: an adversary, Mallory,
- 49. Chapter 6 Other Security Building Blocks One-way Authentication Using Public-Key Cryptography Alice sends a nonce
- 50. Chapter 6 Other Security Building Blocks One-way Authentication Using Public-Key Cryptography Another challenge-and-response authentication protocol:
- 51. Chapter 6 Other Security Building Blocks Authentication and Key-Exchange Protocols Combine authentication and key-exchange Assume
- 52. Chapter 6 Other Security Building Blocks Authentication and Key-Exchange Protocols Wide-Mouth Frog C: => S(C,Encrypt((D,KCD,TC),KCS));
- 53. Chapter 6 Other Security Building Blocks Authentication and Key-Exchange Protocols Yahalom C => D (C,NC);
- 54. Chapter 6 Other Security Building Blocks Authentication and Key-Exchange Protocols Denning and Sacco (public-key) Carla
- 55. Chapter 6 Other Security Building Blocks Authentication and Key-Exchange Protocols A weakness of the Denning
- 56. Chapter 6 Other Security Building Blocks Authentication and Key-Exchange Protocols Fixing the Denning and Sacco
- 57. Chapter 6 Other Security Building Blocks Motivation for Zero Knowledge Proofs Many challenge and response
- 58. Chapter 6 Other Security Building Blocks Zero-Knowledge Proofs Alice can perform a zero-knowledge proof so
- 59. Chapter 6 Other Security Building Blocks Zero-Knowledge Proofs (cont) Bob asks Alice up to n
- 60. Chapter 6 Other Security Building Blocks The Zero-Knowledge Cave A cave with a single entrance
- 61. Chapter 6 Other Security Building Blocks The Zero-Knowledge Cave (cont)
- 62. Chapter 6 Other Security Building Blocks The Zero-Knowledge Cave (cont) Alice can prove to Bob
- 63. Chapter 6 Other Security Building Blocks The Zero-Knowledge Cave There are four possiblities: (1) Alice
- 64. Chapter 6 Other Security Building Blocks The Zero-Knowledge Cave (cont) No matter how many times
- 65. Chapter 6 Other Security Building Blocks Mathematical Background - Graph Isomorphism A graph is a
- 66. Chapter 6 Other Security Building Blocks Graph Isomorphism Graphs (I) and (II) are isomorphic: (I)
- 67. Chapter 6 Other Security Building Blocks Graph Isomorphism (cont) Graphs (II) and (III) are isomorphic:
- 68. Chapter 6 Other Security Building Blocks Graph Isomorphism (cont) Graphs (I) and (III) must be
- 69. Chapter 6 Other Security Building Blocks Graph Isomorphism is a Hard Problem In general, determining
- 70. Chapter 6 Other Security Building Blocks A Zero-Knowledge Proof Using Graph Isomorphism Alice creates two
- 71. Chapter 6 Other Security Building Blocks Zero-Knowledge Proof Using Graph Isomorphism Alice randomly permutes G1
- 72. Chapter 6 Other Security Building Blocks Zero-Knowledge Proof Using Graph Isomorphism Alice and Bob repeat
- 73. Chapter 6 Other Security Building Blocks Zero-Knowledge Proof Using Graph Isomorphism Without knowing the isomorphism
- 74. Chapter 6 Other Security Building Blocks Zero-Knowledge Proof Using Graph Isomorphism Alice only sends one
- 75. Chapter 6 Other Security Building Blocks Zero-Knowledge Proof Using Graph Isomorphism If Alice is able
- 76. Chapter 6 Other Security Building Blocks Problem With Zero-Knowledge Proofs Remember the man-in-the-middle attack? Carol
- 78. Скачать презентацию