Abstract. Quantum computing – is an advanced technology which has a great impact on the traditional methods of computation causing a major challenge for the cryptographic systems that form the basis of our digital security. This research thesis is on cryptographic resilience in the age of quantum when the public key algorithms such as RSA and elliptic curve cryptography get compromised with the use of Shor’s algorithm, while symmetric primitives additionally lose half of their security against Grover’s search. The aim of the research is to thoroughly understand the quantum threat model and through experiments, figure out what is the realistic “cost of quantum safety” for the classical and post-quantum cryptographic mechanisms. The methodology combines systematic literature review with an experiment which is carried out using a reproducible benchmarking framework that (QCCB) outputs statistical performance estimates (mean, dispersion, and confidence intervals) and machine-readable result artifacts. The experimental findings support the migration viewpoint based on the risk quantified (i) the vulnerability window of RSA, 2048 and other classical public, key schemes, of which (ii) the comparative performance and size characteristics of the post-quantum candidates that agree with the NIST standardization. Furthermore, the study introduces a decision-making oriented evaluation metric, the Security Cost Index (SCI), that facilitates the understanding of a correlation of target security levels with the computational overhead enabling different deployment planning scenarios to be fathomed depending on the existing tradeoffs. The paper argues for migration to post-quantum cryptography that has been standardized, and is measurable, at reproducible and with the figure of the clear trade-off should be the mainstay of the efforts for securing confidentiality, integrity, and authenticity against the “harvest now, decrypt later” risk in the long run.

Keywords: Quantum Computing, Post-Quantum Cryptography, NIST FIPS 203/204/205, ML-KEM, ML-DSA, Cryptographic Resilience, Shor’s Algorithm, Grover’s Algorithm, Hybrid Cryptography, Security Migration, HNDL Attack, Lattice-Based Cryptography