Modern digital security relies heavily on encryption algorithms grounded in difficult math problems, which is the backbone of what’s known as public-key infrastructure (PKI). From securing websites to protecting messaging apps, PKI allows two strangers online (or a client and a server) to establish secret keys and verify identities without having met. This is achieved through asymmetric cryptography (public/private key pairs) that current computers find infeasible to break. For example, algorithms like RSA and elliptic-curve cryptography (ECC) underpin much of today’s secure internet traffic, but the advent of quantum computing threatens to upend these protections.