Experiments to protect against harvest now, decrypt later

Quantum computing needs thousands of qubits to crack the public key encryption we currently rely on and at present the largest (publicly announced) quantum computer only has 433 qubits. The sales pitch for protecting against quantum attacks now is that baddies could be quietly harvesting encrypted data, so that when quantum computers are ready, off they go and decrypt.

There are two main approaches to protect against quantum attacks.

One approach, quantum encryption key distribution (QKD), can be implemented one qubit at a time, e.g., by sending photons along fibre optic cables. Each photon is a realisation of a qubit. HSBC is trialling a QKD approach developed by BT and Toshiba, which builds on BB84 from forty years ago. I’ve attempted to explain BB84 in a previous blog post.

Vodafone has opted for a non-quantum approach to defend against attacks on crypto by trialling new public key encryption algorithms, on classical computers, that are thought to be quantum-safe: post-quantum cryptography (PQC).

The next major revision of Google Chrome will include a hybrid approach combining X25519 , a standard method already used by Chrome and others browsers, with Kyber-768, a PQC method that has so far resisted attack.

Since PQC methods are new, the hybrid approach offers protection while the maths continues to be stress-tested. This is important since there has already beenΒ an embarrassingly quick crack of a supposedly quantum-safe approach.