> I really struggle to understand what this all is good for. Defence? If your secrets (or more likely, your nation's secrets) might be exposed by a quantum at

> I really struggle to understand what this all is good for. Defence? If your secrets (or more likely, your nation's secrets) might be exposed by a quantum attack, then you'd better understand how such an attack might work, so you can defend against it. Nations (some) do research into chemical/biological weapons to learn how to defend against them (purportedly). That's a "devil's advocate" answer. I lean to the view that, for very big secrets, it's better not to have a secret at all. At least, don't have secrets that need to be kept long-term. That sounds glib and handwavy, and it is; but most secrets seem to get out, sooner rather than later, and usually not as a result of someone cracking the cryptography.