[Jeff Winston]

That may sound limiting but it still allows each node to send a one-time pad to the hub which it then uses to communicate securely over a classical link. The hub can then route this message to another node using another one time pad that it has set up with this second node. So the entire network is secure, provided that the central hub is also secure.

So... if I understand correctly.

We already knew how to create a perfect, unbreakable cipher. It simply requires knowing the key.

The problem, until now, has been an inability to transmit a perfectly-unbreakable cipher key, in such a way that it could not be intercepted.

This system solves that problem by relying on the principle that quantum information can't be read without being destroyed.

End points generate a key for perfect, unbreakable encryption and transmit it, using quantum information, to the central hub.

Now the central hub shares a common unbreakable key with every end point. Voila. Perfectly secure communication can take place in either direction. And two end points can communicate by going through the hub.

So as long as the hub's secure, all communications is secure.

[Bryan24]

I’m guessing the United States Government would hire a Chinese company to design the security for the hub....

[UCANSEE2]

Or... as long as you don’t try to read the encryption key, you can read all the data.

[Jeff Winston]

Claude Shannon proved, using information theory considerations, that the one-time pad has a property he termed perfect secrecy; that is, the ciphertext C gives absolutely no additional information about the plaintext. This is because, given a truly random key which is used only once, a ciphertext can be translated into any plaintext of the same length, and all are equally likely.

So because the key is perfectly random (and the same length as the message) the only information that is conveyed by having the text is the maximum length of the message.

The completely random key completely randomizes every character of the message. So it doesn't matter if your opponent has all the computing power in the entire universe. Until the key is known, or at least part of it, the message can't be cracked.

The end result is like, "I sent a message to Bob that's 225 characters long. Or maybe less. Maybe I put some filler in just to make it even more inscrutable. So guess what I said?"

[rightwingcrazy]

How do you ensure that the central hub is secure?