Paper 2023/1355

Security Proofs for Key-Alternating Ciphers with Non-Independent Round Permutations

Liqing Yu, East China Normal University, Shanghai Qi Zhi Institute
Yusai Wu, Shanghai Qi Zhi Institute
Yu Yu, Shanghai Jiao Tong University, Shanghai Qi Zhi Institute
Zhenfu Cao, East China Normal University
Xiaolei Dong, East China Normal University

This work studies the key-alternating ciphers (KACs) whose round permutations are not necessarily independent. We revisit existing security proofs for key-alternating ciphers with a single permutation (KACSPs), and extend their method to an arbitrary number of rounds. In particular, we propose new techniques that can significantly simplify the proofs, and also remove two unnatural restrictions in the known security bound of 3-round KACSP (Wu et al., Asiacrypt 2020). With these techniques, we prove the first tight security bound for t-round KACSP, which was an open problem. We stress that our techniques apply to all variants of KACs with non-independent round permutations, as well as to the standard KACs.

Available format(s)
Secret-key cryptography
Publication info
A major revision of an IACR publication in TCC 2023
provable securitykey-alternating cipherKACSPindistinguishabilityrandom permutation modelnon-independent
Contact author(s)
lqyups @ 126 com
yusaiwu @ 126 com
yuyu @ yuyu hk
zfcao @ sei ecnu edu cn
dong-xl @ sei ecnu edu cn
2023-09-13: approved
2023-09-11: received
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Creative Commons Attribution


      author = {Liqing Yu and Yusai Wu and Yu Yu and Zhenfu Cao and Xiaolei Dong},
      title = {Security Proofs for Key-Alternating Ciphers with Non-Independent Round Permutations},
      howpublished = {Cryptology ePrint Archive, Paper 2023/1355},
      year = {2023},
      note = {\url{}},
      url = {}
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