indifferentiability of confusion diffusion networks
play

Indifferentiability of Confusion- Diffusion Networks Yevgeniy Dodis - PowerPoint PPT Presentation

Indifferentiability of Confusion- Diffusion Networks Yevgeniy Dodis (NYU), Martijn Stam (Bristol), John Steinberger (Tsinghua), Tianren Liu (MIT) Wednesday, May 11, 16 Indifferentiability of Confusion- Diffusion Networks Yevgeniy Dodis (NYU),


  1. Indifferentiability of Confusion- Diffusion Networks Yevgeniy Dodis (NYU), Martijn Stam (Bristol), John Steinberger (Tsinghua), Tianren Liu (MIT) Wednesday, May 11, 16

  2. Indifferentiability of Confusion- Diffusion Networks Yevgeniy Dodis (NYU), Martijn Stam (Bristol), John Steinberger (Tsinghua), Liu Tianren (MIT) Wednesday, May 11, 16

  3. Substitution-Permutation Network (ex: AES): S S S S S S S S π π π π S S S S k 0 k 1 k 2 k 3 k 4 S S S S Wednesday, May 11, 16

  4. Substitution-Permutation Network (ex: AES): S S S S S S S S π π π π S S S S k 0 k 1 k 2 k 3 k 4 S S S S S-boxes (small input size) (permutations!) Wednesday, May 11, 16

  5. Substitution-Permutation Network (ex: AES): S S S S S S S S π π π π S S S S k 0 k 1 k 2 k 3 k 4 S S S S S-boxes “Diffusion” (small input size) (permutations!) Permutations (big input size, simple structure) Wednesday, May 11, 16

  6. Substitution-Permutation Network (ex: AES): S S S S S S S S π π π π S S S S k 0 k 1 k 2 k 3 k 4 S S S S S-boxes Subkeys! “Diffusion” (small input size) (permutations!) Permutations (big input size, simple structure) Wednesday, May 11, 16

  7. Confusion-Diffusion Network: S S S S S S S S S S π π π π S S S S S S S S S S Wednesday, May 11, 16

  8. Confusion-Diffusion Network: S S S S S S S S S S π π π π S S S S S S S S S S ...same, but no keys! Wednesday, May 11, 16

  9. Confusion-Diffusion Network: S S S S S S S S S S π π π π S S S S S S S S S S ...same, but no keys! • can be seen as a domain extension mechanism for permutations (from S-box to “full” permutation) Wednesday, May 11, 16

  10. Confusion-Diffusion Network: S S S S S S S S S S π π π π S S S S S S S S S S ...same, but no keys! • can be seen as a domain extension mechanism for permutations (from S-box to “full” permutation) • terminology goes back to Shannon (1949), but the design paradigm seems to be Feistel’s (1970) Wednesday, May 11, 16

  11. This work’s high-level goals • Investigate the theoretical soundness of CD (confusion-diffusion!) networks as a design paradigm for cryptographic permutations • Fundamental question: (efficient) domain extension of a public random permutation • Work in an ideal model (S-boxes are independent random permutations, D-boxes are fixed, explicit permutations) • Does the network “emulate” a random permutation? How many rounds are necessary, and what kinds of D-boxes do we need?? Wednesday, May 11, 16

  12. This work’s high-level goals • Investigate the theoretical soundness of CD (confusion-diffusion!) networks as a design paradigm for cryptographic permutations • Fundamental question: (efficient) domain extension of a public random permutation • Work in an ideal model (S-boxes are independent random permutations, D-boxes are fixed, explicit permutations) • Does the network “emulate” a random permutation? How many rounds are necessary, and what kinds of D-boxes do we need?? Wednesday, May 11, 16

  13. This work’s high-level goals • Investigate the theoretical soundness of CD (confusion-diffusion!) networks as a design paradigm for cryptographic permutations • Fundamental question: (efficient) domain extension of a public random permutation • Work in an ideal model (S-boxes are independent random permutations, D-boxes are fixed, explicit permutations) • Does the network “emulate” a random permutation? How many rounds are necessary, and what kinds of D-boxes do we need?? Wednesday, May 11, 16

  14. This work’s high-level goals • Investigate the theoretical soundness of CD (confusion-diffusion!) networks as a design paradigm for cryptographic permutations • Fundamental question: (efficient) domain extension of a public random permutation • Work in an ideal model (S-boxes are independent random permutations, D-boxes are fixed, explicit permutations) • Does the network “emulate” a random permutation? How many rounds are necessary, and what kinds of D-boxes do we need?? Wednesday, May 11, 16

  15. vaguely related work • Miles & Viola prove an indistinguishability result for SPN networks where the S-boxes are secret (part of the key) and one-way (so not really an SPN network after all) Wednesday, May 11, 16

  16. vaguely related work CD indifferentiability • Miles & Viola prove an indistinguishability result for SPN networks where the S-boxes are secret (part of the key) and one-way (so not really an SPN network after all) public two-way Wednesday, May 11, 16

  17. S 1 , 3 S 2 , 3 S 3 , 3 S 4 , 3 S 1 , 2 S 2 , 2 S 3 , 2 S 4 , 2 π 1 π 2 π 3 S 1 , 1 S 2 , 1 S 3 , 1 S 4 , 1 Wednesday, May 11, 16

  18. n S 1 , 3 S 2 , 3 S 3 , 3 S 4 , 3 n S 1 , 2 S 2 , 2 S 3 , 2 S 4 , 2 π 1 π 2 π 3 n S 1 , 1 S 2 , 1 S 3 , 1 S 4 , 1 n = wire length Wednesday, May 11, 16

  19. n S 1 , 3 S 2 , 3 S 3 , 3 S 4 , 3 n w = 3 S 1 , 2 S 2 , 2 S 3 , 2 S 4 , 2 π 1 π 2 π 3 n S 1 , 1 S 2 , 1 S 3 , 1 S 4 , 1 n = wire length w = “width” (no. S-boxes per round) Wednesday, May 11, 16

  20. r = 4 n S 1 , 3 S 2 , 3 S 3 , 3 S 4 , 3 n w = 3 S 1 , 2 S 2 , 2 S 3 , 2 S 4 , 2 π 1 π 2 π 3 n S 1 , 1 S 2 , 1 S 3 , 1 S 4 , 1 n = wire length w = “width” (no. S-boxes per round) r = number of rounds Wednesday, May 11, 16

  21. { 0 , 1 } wn = domain of CD network r = 4 n S 1 , 3 S 2 , 3 S 3 , 3 S 4 , 3 n w = 3 S 1 , 2 S 2 , 2 S 3 , 2 S 4 , 2 π 1 π 2 π 3 n S 1 , 1 S 2 , 1 S 3 , 1 S 4 , 1 n = wire length w = “width” (no. S-boxes per round) r = number of rounds Wednesday, May 11, 16

  22. Security Model (indifferentiability) ? D ? ? Wednesday, May 11, 16

  23. Security Model (indifferentiability) REAL WORLD ? D ? IDEAL WORLD ? Wednesday, May 11, 16

  24. Security Model (indifferentiability) REAL WORLD S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 2 S 2 , 2 S 3 , 2 π 1 π 2 ? S 1 , 1 S 2 , 1 S 3 , 1 D ? IDEAL WORLD ? Wednesday, May 11, 16

  25. Security Model (indifferentiability) REAL WORLD S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 2 S 2 , 2 S 3 , 2 S 1 , 2 S 2 , 2 S 3 , 2 π 1 π 2 ? S 1 , 1 S 2 , 1 S 3 , 1 S 1 , 1 S 2 , 1 S 3 , 1 D ? IDEAL WORLD ? Wednesday, May 11, 16

  26. Security Model (indifferentiability) REAL WORLD S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 2 S 2 , 2 S 3 , 2 S 1 , 2 S 2 , 2 S 3 , 2 π 1 π 2 ? S 1 , 1 S 2 , 1 S 3 , 1 S 1 , 1 S 2 , 1 S 3 , 1 D ? IDEAL WORLD ? Q Wednesday, May 11, 16

  27. Security Model (indifferentiability) REAL WORLD S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 2 S 2 , 2 S 3 , 2 S 1 , 2 S 2 , 2 S 3 , 2 π 1 π 2 ? S 1 , 1 S 2 , 1 S 3 , 1 S 1 , 1 S 2 , 1 S 3 , 1 D ? Insert Simulator IDEAL WORLD ? Here Q Wednesday, May 11, 16

  28. Security Model (indifferentiability) REAL WORLD S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 2 S 2 , 2 S 3 , 2 S 1 , 2 S 2 , 2 S 3 , 2 π 1 π 2 ? S 1 , 1 S 2 , 1 S 3 , 1 S 1 , 1 S 2 , 1 S 3 , 1 D ? Insert Simulator IDEAL WORLD ? S S S Here Q S S S S S S Wednesday, May 11, 16

  29. Security Model (indifferentiability) REAL WORLD S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 2 S 2 , 2 S 3 , 2 S 1 , 2 S 2 , 2 S 3 , 2 π 1 π 2 ? S 1 , 1 S 2 , 1 S 3 , 1 S 1 , 1 S 2 , 1 S 3 , 1 D ? Insert Simulator IDEAL WORLD ? S S S Here Q S S S S S S S Q Goal: By using oracle access to the simulator has to make up answers that look “consistent” with Q Wednesday, May 11, 16

  30. Security Model (indifferentiability) REAL WORLD S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 2 S 2 , 2 S 3 , 2 S 1 , 2 S 2 , 2 S 3 , 2 π 1 π 2 “For so-and-so many rounds, for such-and-such ? S 1 , 1 S 2 , 1 S 3 , 1 S 1 , 1 S 2 , 1 S 3 , 1 diffusion permutations, and with such-and-such D a simulator, the distinguisher cannot distinguish ? Insert Simulator using so-and-so-many queries.” IDEAL WORLD ? S S S Here Q S S S S S S ⊆ { Q Goal: By using oracle access to the simulator has to make up answers that look “consistent” with Q Wednesday, May 11, 16

  31. Security Model (indifferentiability) REAL WORLD S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 3 S 2 , 3 S 3 , 3 S 1 , 2 S 2 , 2 S 3 , 2 S 1 , 2 S 2 , 2 S 3 , 2 π 1 π 2 “For so-and-so many rounds, for such-and-such ? S 1 , 1 S 2 , 1 S 3 , 1 S 1 , 1 S 2 , 1 S 3 , 1 diffusion permutations, and with such-and-such D a simulator, the distinguisher cannot distinguish ? Insert Simulator using so-and-so-many queries.” IDEAL WORLD ? S S S Here Q S S S S S S ⊆ { Q Goal: By using oracle access to the simulator has to make up answers that look “consistent” with Q Wednesday, May 11, 16

  32. Combinatorial Properties of the Diffusion Permutations, by name: 1. Entry-Wise Randomized Preimage Resistance (RPR) 2. Entry-Wise Randomized Collision Resistance (RCR) 3. Conductance (& “all-but-one Conductance”) Wednesday, May 11, 16

  33. RPR $ → x 1 ? = y ∗ x 2 y 2 2 π x 3 x 4 Wednesday, May 11, 16

  34. RPR $ → x 1 ? = y ∗ x 2 y 2 2 π x 3 x 4 For any fixed values of , and x 2 x 3 , and for any , there is low y ∗ x 4 2 probability that over the y 2 = y ∗ 2 randomness in x 1 Wednesday, May 11, 16

  35. RCR $ → x 1 ? = y ′ x 2 , x ′ y 2 2 2 π x 3 , x ′ 3 x 4 , x ′ 4 Wednesday, May 11, 16

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend