QUANTUM COMPUTING THREATS TO CLASSICAL CRYPTOGRAPHIC MECHANISMS: A SURVEY OF POST‑QUANTUM CRYPTOGRAPHY READINESS

Abstract

The rapid advancement of quantum computing poses a fundamental threat to classical cryptographic mechanisms that underpin modern digital security. Shor’s algorithm can efficiently solve integer factorization and discrete logarithm problems, thereby breaking widely used public-key cryptosystems such as RSA, ECC, and Diffie–Hellman. Grover’s algorithm also reduces the effective security of symmetric encryption and hash functions by half. This paper provides a systematic analysis of the impact of quantum attacks on current cryptographic infrastructures, including TLS, digital signatures, and blockchain. We then review the state of post-quantum cryptography (PQC) as standardized by NIST, focusing on three leading candidates: CRYSTALS-Kyber for key encapsulation, and CRYSTALS-Dilithium and FALCON for digital signatures. Through simulation using the Open Quantum Safe (liboqs) library on a standard x86_64 platform, we measure key generation time, encryption/signing speed, decryption/verification latency, and key/signature sizes. Our results show that Kyber-768 achieves key generation in <0.1 ms and produces public keys of about 1.2 KB, while Dilithium-3 generates signatures of ~2.7 KB with verification times under 0.3 ms. Compared to RSA-2048 and ECDSA-P256, PQC algorithms offer competitive performance at the cost of larger key and signature sizes. Based on these findings, we propose a hybrid transition roadmap that combines classical and PQC algorithms in parallel, minimizing risk while maintaining backward compatibility. The paper concludes that organizations should begin immediate preparations for the post-quantum era, especially for data requiring long-term confidentiality.