Quantum technologies are moving from theory to practice, promising significant advances in computation across science and industry. The same capabilities, however, undermine the cryptographic assumptions that underpin today’s secure communications. Public-key schemes such as Rivest-Shamir-Adleman (RSA) and Elliptic-Curve Cryptography (ECC), whose security relies on the hardness of integer factorisation and discrete logarithms, are susceptible to quantum algorithms that solve these problems efficiently. Anticipating this shift, the National Institute of Standards and Technology (NIST) has launched a post-quantum standardisation programme, culminating in the first FIPS for quantum-resistant primitives. In parallel, widely deployed security protocols are evolving: TLS at the application edge and IPsec at the network layer, with IKEv2 extensions enabling hybrid and post-quantum key establishment while preserving interoperability.