Successful Attack Against a Quantum Cryptography System

If you encode something via any classical crypto system (e.g. RSA) it's usually based on something that is computationally difficult to crack rather than something that is impossible to crack. You can usually find somebody willing to tell you it will somewhere on the order of thousands of years to crack that message, even assuming Moore's law growing resources. That's utter crap. In reality, algorithms continually evolve such that encryption algorithms become insecure in a matter of decades, and that's without disruptive algorithms/tech. (e.g. Quantum computing will shake things up bigtime if and when it happens, but 4096 bit RSA will probably be toast long before that happens.)

Here's where things get scary. Any encrypted message you send today that is encrypted classically can be archived by an eavesdropper without your knowledge and cracked at any point in the future. Your credit card info is going to change before that's likely to happen, but what about your medical records? If information is going to remain sensitive for decades or more, it's already idiotic to protect it with classical encryption.

So how is quantum crypto different? Why can't an eavesdropper just archive a quantum encrypted message and crack it at their leisure the way they can with a classically encrypted message? The answer boils down to the no-cloning theorem, which I encourage you to look into if you're interested. To be brief, quantum crypto algorithms rely on exchanges of quantum states that, if an eavesdropper attempts to intercept and copy, will introduce errors that will alert the sender/receiver to the fact that they are being eavesdropped upon. With quantum crypto, an eavesdropper can obtain no information unless she has an attack that works at the time the message is sent. The attack mentioned in the article is no different. This isn't like DES, where the vulnerability means that all past messages sent can now be trivially cracked. It means that future messages might be compromised if upgrades are not made, but that's it.

With quantum crypto you only have to worry about attacks that can be made with existing knowledge and technology, not all attacks that could be made in the future. If you send a message via quantum crypto and it's safe when you send it, it will be safe for all time. Not just for a while like with classical crypto.

Classical encryption is not safe. It's safe for a while. Quantum crypto is actually safe.