[Resource Topic] 2019/244: Attacks Only Get Better: How to Break FF3 on Large Domains

Welcome to the resource topic for 2019/244

Title:
Attacks Only Get Better: How to Break FF3 on Large Domains

Authors: Viet Tung Hoang, David Miller, Ni Trieu

Abstract:

We improve the attack of Durak and Vaudenay (CRYPTO’17) on NIST Format-Preserving Encryption standard FF3, reducing the running time from O(N^5) to O(N^{17/6}) for domain Z_N \times Z_N. Concretely, DV’s attack needs about 2^{50} operations to recover encrypted 6-digit PINs, whereas ours only spends about 2^{30} operations. In realizing this goal, we provide a pedagogical example of how to use distinguishing attacks to speed up slide attacks. In addition, we improve the running time of DV’s known-plaintext attack on 4-round Feistel of domain Z_N \times Z_N from O(N^3) time to just O(N^{5/3}) time. We also generalize our attacks to a general domain Z_M \times Z_N, allowing one to recover encrypted SSNs using about 2^{50} operations. Finally, we provide some proof-of-concept implementations to empirically validate our results.

ePrint: https://eprint.iacr.org/2019/244

Talk: https://www.youtube.com/watch?v=C0sL2TmUA3Q

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