It isn't quantum computing that will pose any practical challenges to current protocols, but, rather, the improvements in ``classical'' computing software and hardware; which has, always, been the case. It may make for sensationalist headlines, but quantum computing is, still, at an experimental stage. By the time it becomes standard, security procedures, as all other aspects of computing, will, inevitably, have evolved. Cyber security isn't being threatened by the advances in quantum computing, but by classical botnets and the solution, beyond some point is social, not technical. 

No key distribution system offers any ``panacea''. Control of servers is the more important issue. 

The term ``quantum internet'' is, still, more science fiction than fact-and no system is hacker-proof, since social engineering, still, trumps any security measure that involves humans. The issue is to control the risk of a security compromise-typically through backup and insurance. 

It isn't quantum computing that will pose any practical challenges to current protocols, but, rather, the improvements in ``classical'' computing software and hardware; which has, always, been the case. It may make for sensationalist headlines, but quantum computing is, still, at an experimental stage. By the time it becomes standard, security procedures, as all other aspects of computing, will, inevitably, have evolved. Cyber security isn't being threatened by the advances in quantum computing, but by classical botnets and the solution, beyond some point is social, not technical. 

No key distribution system offers any ``panacea''. Control of servers is the more important issue. 

The term ``quantum internet'' is, still, more science fiction than fact-and no system is hacker-proof, since social engineering, still, trumps any security measure that involves humans. The issue is to control the risk of a security compromise-typically through backup and insurance. 

Well, so there are a couple fundamental principles in quantum key distribution that are very similar/exactly identical to the methodology of using entanglement as a resource in quantum computing.

I wrote out something a lot longer detailing the complexity involved in setting up a quantum internet, but in essence it's very simple: Alice has a router, so does Bob; Alice and Bob have qubits which are entangled with their routers, and the routers have qubits which are entangled with qubits on other routers. Quantum entanglement from Bob to Alice is achieved by performing local (internal to the routers) entanglement operations between the sets of qubits which follow the path between Alice and Bob. Alice's ability to send information to Bob is limited by the number of hops between her and Bob - each hop increases the Von Neumann entropy of the entanglement, thus requiring an increase of classical communication to perform superdense coding (or QKD).

In essence, a quantum internet is ideally represented by a single, very large quantum "router" which everyone has a bank of qubits entangled to. The router simply performs entanglement linkage according to instructions from the sender.

As I understand it, there is no danger in this interlocking entanglement router as QKD is concerned. Even if there is a man-in-the-middle "stealing qubits" from the router, their interactions with the system (measurements) will give rise to noise in Bob's measurement. This is the essence of QKD and the general schema of security behind quantum information; you can't copy a quantum state, and any attempt to extract information from a set of other observers will cause a change in those observers' observations.

There's also not even a need for satellites :) we can keep using our regular routers, we just need a giant supernode which we stick a bunch of qubit hard drives in. How we populate those hard drives? A bit harder, but a node structure does simplify it. How much bandwidth we want to have is inversely related to the number of nodes we use, and directly proportional to the amount of quantum computational power we have on Bob's side.

Hope this helps. I think we will have a quantum internet at some point, but it's much too difficult to construct right now; we simply don't have the hardware. Realistic quantum computing requires qubits in the trillions or more (just to do basic stuff) - and the most we can do right now is like, fifteen or so...without entanglement across long distances. Movement of nodes, or even just heat in general, causes huge increases in entanglement entropy, requiring exponentially larger numbers of qubits for error correction. Some recent advancements in condensed matter physics have come up with understanding of entanglement propagation in simple systems, but there's a lot left to figure out.

Thank you Dk Matai for, what I consider to be a most relevant and interesting question. I'd like to provide a balanced answer, validating your question and its replies, and hopefully leaving us with likely food for thought and intensified research.

Stam Nicolis stated: "Cyber security isn't being threatened by the advances in quantum computing,..." and

Henry Tregillus stated: "I think we will have a quantum internet at some point, but it's much too difficult to construct right now; we simply don't have the hardware."

My view is, we already have a quantum internet, it is natural, entangled, all around us and I suspect physically in place in a form we have not recognized yet. How it works exactly is a question for us systems thinkers and designers to start figuring out.

I like the simplistic view of a quantum router and its application across nodes. However, I'd like ot upset our apple cart a little, if I may?

DNA editing, as a form of quantum-data intervention, is already happening (China's 2015 announcement in this regard).

1) I think quantum encoding of any kind totally threatens data security in ways we have not even started imagining yet. 

2) We have no proper idea to what extent non-standard entanglement theory would go, but in theory, it would be possible to encrypt data in an atom and send it anywhere in the universe. We would also theoretically be able to physically retrieve any referenced code from the universe.

Key question for me is: where is the existing quantum grid on earth, as a supernet, and how does it work? We know of at least one coding algorithm that uses it (QKD). All things remaining equal, there must be more. Is this in reality then Pandora's box that is busy being opened?