Paper 2021/653

Smooth Zero-Knowledge Hash Functions

Behzad Abdolmaleki, Hamidreza Khoshakhlagh, and Helger Lipmaa


We define smooth zero-knowledge hash functions (SZKHFs) as smooth projective hash functions (SPHFs) for which the completeness holds even when the language parameter lpar and the projection key HP were maliciously generated. We prove that blackbox SZKHF in the plain model is impossible even if lpar was honestly generated. We then define SZKHF in the registered public key (RPK) model, where both lpar and HP are possibly maliciously generated but accepted by an RPK server, and show that the CRS-model trapdoor SPHFs of Benhamouda et al. are also secure in the weaker RPK model. Then, we define and instantiate subversion-zero knowledge SZKHF in the plain model. In this case, both lpar and HP are completely untrusted, but one uses non-blackbox techniques in the security proof.

Available format(s)
Cryptographic protocols
Publication info
Preprint. MINOR revision.
plain modelRPK modelSPHFtrapdoor SPHFsubversion zero-knowledge
Contact author(s)
hamidreza @ cs au dk
2021-05-20: received
Short URL
Creative Commons Attribution


      author = {Behzad Abdolmaleki and Hamidreza Khoshakhlagh and Helger Lipmaa},
      title = {Smooth Zero-Knowledge Hash Functions},
      howpublished = {Cryptology ePrint Archive, Paper 2021/653},
      year = {2021},
      note = {\url{}},
      url = {}
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