Why is this a problem that can’t wait until large-scale quantum computers arrive?

That is part of why this feels urgent now, even though large-scale quantum computers are not available yet.

That said, this is not something quantum computers can do today.

Post-quantum cryptography is a new generation of algorithms designed to stay secure even against powerful quantum computers.

Rather than relying on mathematical problems that a quantum computer could eventually solve, these algorithms are built on different types of problems that researchers believe are hard for both classical and quantum computers to crack.