How to fake zero-knowledge proofs, again

Véronique Cortier (1) , Pierrick Gaudry (2) , Quentin Yang (1, 3)

1 PESTO - Proof techniques for security protocols
2 CARAMBA - Cryptology, arithmetic : algebraic methods for better algorithms
3 X - École polytechnique

In 2012, Bernhard et al. showed that the Fiat-Shamir heuristic must be used with great care in zero-knowledge proofs. We explain how, in the Belenios voting system, while not using the weak version of Fiat-Shamir, there is still a gap that allows to fake a zero-knowledge proof in certain circumstances. Therefore an attacker who corrupts the voting server and the decryption trustees could break verifiability.

Domaines: Cryptographie et sécurité [cs.CR]

Véronique Cortier, Pierrick Gaudry, Quentin Yang. How to fake zero-knowledge proofs, again. E-Vote-Id 2020 - The International Conference for Electronic Voting, Oct 2020, Bregenz / virtual, Austria. ⟨hal-02928953⟩