Crooked indifferentiability of the Feistel Construction
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arXiv
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| Auteurs principaux: | , , |
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| Format: | Preprint |
| Publié: |
2024
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| _version_ | 1866917639459176448 |
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| author | Russell, Alexander Tang, Qiang Zhu, Jiadong |
| author_facet | Russell, Alexander Tang, Qiang Zhu, Jiadong |
| contents | The Feistel construction is a fundamental technique for building pseudorandom permutations and block ciphers. This paper shows that a simple adaptation of the construction is resistant, even to algorithm substitution attacks -- that is, adversarial subversion -- of the component round functions. Specifically, we establish that a Feistel-based construction with more than $2000n/\log(1/ε)$ rounds can transform a subverted random function -- which disagrees with the original one at a small fraction (denoted by $ε$) of inputs -- into an object that is \emph{crooked-indifferentiable} from a random permutation, even if the adversary is aware of all the randomness used in the transformation. We also provide a lower bound showing that the construction cannot use fewer than $2n/\log(1/ε)$ rounds to achieve crooked-indifferentiable security. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_09450 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Crooked indifferentiability of the Feistel Construction Russell, Alexander Tang, Qiang Zhu, Jiadong Cryptography and Security The Feistel construction is a fundamental technique for building pseudorandom permutations and block ciphers. This paper shows that a simple adaptation of the construction is resistant, even to algorithm substitution attacks -- that is, adversarial subversion -- of the component round functions. Specifically, we establish that a Feistel-based construction with more than $2000n/\log(1/ε)$ rounds can transform a subverted random function -- which disagrees with the original one at a small fraction (denoted by $ε$) of inputs -- into an object that is \emph{crooked-indifferentiable} from a random permutation, even if the adversary is aware of all the randomness used in the transformation. We also provide a lower bound showing that the construction cannot use fewer than $2n/\log(1/ε)$ rounds to achieve crooked-indifferentiable security. |
| title | Crooked indifferentiability of the Feistel Construction |
| topic | Cryptography and Security |
| url | https://arxiv.org/abs/2404.09450 |