NISQ-Era Threat Assessment: Evaluating Quantum-Classical Hybrid Attacks on RSA Security

NIST’s first post-quantum cryptography (PQC) standards, finalized in August 2024, have increased the urgency of enterprise migration. While Shor’s algorithm is still a distant threat for fault-tolerant systems, the near-term security landscape is shaped by today’s NISQ devices and hybrid classical-quantum paradigms.

The Bavarian research project VerQueRD (Verschlüsselung brechen mittels Quanten-Reduktions- und Dekompositionsmethoden) targets the need for methodological certainty in migration timelines. The consortium — DATEV eG (KRITIS operator and project lead), infoteam Software AG, and Fraunhofer IIS — evaluates whether combinatorial optimization and quantum-inspired methods can accelerate integer factorization enough to threaten current asymmetric standards.

VerQueRD departs from traditional gate-based attacks and studies factorization via three parallel vectors:

• Gate-based NISQ (QAOA + Automated Circuit Cutting): Utilizing graph-shrinking, optimal QUBO reduction, and circuit cutting to enable execution of larger QAOA circuits on limited NISQ hardware to scale factorization capabilities within NISQ-compatible circuit depth constraints.
• Quantum Annealing: Mapping factorization to constrained topology-aware optimization landscapes using advanced reduction techniques.
• Quantum-inspired classical (Tree Tensor Network Sieving / CVP): Leveraging tensor network decompositions and closest vector problem formulations to target 200-bit factorization.

Combining algorithmic benchmarks with resource extrapolation, the project provides actionable evidence for KRITIS-relevant security roadmaps. The talk presents VerQueRD’s roadmap and 2028 targets: a hardware-validated framework quantifying how far near-term quantum technologies can advance toward breaking cryptographically relevant encryption — giving enterprises a robust basis for post-quantum transition planning.