Abstract

Quantum computing is introducing a significant transformation in cybersecurity by creating both new security capabilities and new threats to established cryptographic systems. Large-scale fault-tolerant quantum computers could undermine widely deployed public-key cryptographic mechanisms through quantum algorithms such as Shor’s algorithm, while Grover’s algorithm provides a quadratic search advantage that affects the security analysis of symmetric cryptography. At the same time, quantum technologies offer defensive mechanisms including quantum key distribution, quantum random number generation, quantum-safe authentication, and advanced security architectures. Post-Quantum Cryptography (PQC) has therefore emerged as an essential strategy for protecting conventional communication systems against future quantum attacks. In August 2024, NIST finalized three principal PQC standards: ML-KEM, ML-DSA, and SLH-DSA, and in March 2025 selected HQC as an additional key-establishment algorithm for standardization. This article examines the applications of quantum computing in cybersecurity and cryptographic systems, emphasizing quantum threats, cryptanalysis, quantum key distribution, quantum-safe cryptography, secure communications, intrusion detection, random number generation, and migration strategies. Graph-ready comparative datasets are provided for cryptographic vulnerability, cybersecurity applications, implementation challenges, and quantum- resistant protection mechanisms. The analysis shows that quantum computing should be considered simultaneously as a future attack capability and as a technology that can contribute to stronger security architectures.