Hidden Subgroup Problem
2026-06-15 10:00 - 11:00 (Europe/Bucharest) | Facultatea de Matematica si Informatica, sala S.213
Title: Hidden subgroup problem
Speaker: Mihai Prunescu (UB)

Abstract:A subgroup H of G = F2 x …. x F2 is implicitly given by a function rho on G. The function rho is constant on classes H+x. A classical quantum algorithm is able to find a generating set of H.

Acknowledgement: This seminar talk is (in part) due to Q-FENCE, Programme HORIZON.2.3 – Civil Security for Society, grant agreement ID: 101225708.

This project has received funding from the European Unions Horizon Europe research and innovation programme under grant agreement No. 101225708 as well as the Swiss State Secretariat for Education, Research and Innovation (SERI).

Making zkSNARKs Non-Malleable
2026-06-23 14:30 - 16:00 | Facultatea de Matematica si Informatica, sala S.512, Romania
Title: Making zkSNARKs Non-Malleable
Speaker: Antonio Faonio (Eurecom)

Abstract: Zero-knowledge SNARKs (zkSNARKs) are cryptographic proof systems that allow a prover to convince a verifier that a statement is true, with very small proofs and fast verification, without revealing the underlying witness. The standard security notion for SNARKs is knowledge soundness, which guarantees that any prover who convinces the verifier must “know” a valid witness. A stronger notion is simulation extractability, which ensures that even an adversary who has seen simulated proofs cannot create a new valid proof without actually knowing a witness, and in particular implies non-malleability. This stronger guarantee is especially important in distributed and adversarial settings, where proof malleability can become a real threat. In this talk, we revisit simulation extractability for universal zkSNARKs in the PIOP-to-SNARK paradigm. We discuss how this property can be achieved and analyzed in systems used in practice, with particular attention to optimizations such as the linearization trick. We also place these results in a broader context, reviewing existing approaches to simulation extractability in the literature and highlighting alternative techniques and trade-offs. The goal is to give a unified and accessible picture of how simulation extractability can be obtained in modern zkSNARK constructions, and what design choices are needed to ensure it in practice.

Acknowledgement: This seminar talk is due to the PATTERN CHIST-ERA project https://chistera-pattern.github.io/ ; https://sites.google.com/unibuc.ro/patternub

PATTERN receives funding from the French National Research Agency under Grant Agreement No. ANR-23-CHR4-0008, the Luxembourg National Fund under Grant Agreement No. INTER/CHIST23/17931746, and the Romanian Ministry of Research, Innovation and Digitization, CNCS/CCCDI – UEFISCDI, project number ERANET-CHISTERA-IV-PATTERN, within PNCDI IV.

Quantum Key Distribution - Transitioning to Future Cryptography
2026-06-29 09:30 - 22:30 | Facultatea de Matematica si Informatica, sala S.512, Romania
Title: Quantum Key Distribution – Transitioning to Future Cryptography
Speaker: Andrei Andries (masterand SAL, UB)

Abstract: The talk discusses Quantum Key Distribution (QKD), which marks the transition from mathematics-based to physics-based cryptography. While QKD is in continuous development, there are still unsolved issues (such as long-distance transmission and hardware limitations).
