Encryption and Decryption in Quantum Cryptography

This paper gives a comprehensive review of quantum cryptographic advances in the context of the most critical vulnerabilities that classical encryption schemes have in the era of quantum computing. We compare the vulnerabilities of existing solutions like RSA and ECC to quantum attacks and examine new quantum-resistant solutions like lattice cryptography and Quantum Key Distribution (QKD) schemes. Comparing BB84, E91, and post-quantum solutions, this survey identifies leading challenges in real-world deployment, i.e., photon loss and quantum repeater constraints. Our paper contributes a migration framework towards quantum-secure systems, emphasising hybrid classical-quantum solutions. This work is a research guide and policymaker's companion to quantum-proof cryptographic infrastructure against quantum attacks. Future implementations will incorporate photon polarisation simulations and quantum channel modelling for information-theoretic security.