5 ms·
This article implies that QKD could be a replacement for asymmetric cryptography, which is simply not true. In order to prevent man-in-the-middle attacks, QKD r
by fsh 5y ago
This article implies that QKD could be a replacement for asymmetric cryptography, which is simply not true. In order to prevent man-in-the-middle attacks, QKD requires having a pre-shared key between the participants. If you have that, why not simply use a symmetric-key encryption algorithm (like AES) which cannot be broken by a hypothetical quantum computer?
Another serious drawback is that QKD requires having some kind of direct physical connection between the communicating partners. Even if we had perfect quantum repeaters (which we really don't), this would require going back to 19th century telephone exchanges that physically plug together cables (or fibers in this case). The scaling of a global network would be infinitely worse than the modern packet-switched internet.
At best, QKD could provide a type of forward secrecy against someone stealing your keys or breaking AES in the far future. This comes at the cost of extreme impracticability. Not to speak of the host of side-channel attacks and other implementation vulnerabilities that have been found in commercial QKD systems.
I think that QKD is a fun idea to explore, but I find it really disheartening that these pratical issues are almost never openly discussed in the community. And pop-sci articles usually get pretty much everything wrong about the topic.
- vlovich123 5y agoMaybe not for consumer devices, but maybe to secure the connections of long communication links which are already physically switched (fiber, laser, etc) to protect against MITM?
- Strilanc 5y agoEverything you said is right, except the part about quantum networks needing to do physical circuit switching. For example, consider a series of quantum routers. Each just continuously builds entanglement with its neighbors. When you want to send a qubit to a destination, a path is calculated and routers along the path perform entanglement swapping until you and the receiver share an EPR pair. Then you use that EPR pair to teleport the qubit to the receiver. No cables get moved; it's just changing which qubit pairs are measured in the Bell basis. ...Admittedly this is way beyond current capabilities. It basically requires the routers to be error corrected quantum computers (you need to do entanglement distillation to pump noise out of the system).
- jl2718 5y agoThe pre-shared key is not required, although you don’t really know who you are talking to, so maybe that’s how it’s used. See my response on this: https://news.ycombinator.com/item?id=27412636 https://news.ycombinator.com/item?id=27412636