The News
German physicists working on secure data connection have developed an improved method to transmit data securely from one computer to another, using the ideas of quantum mechanics.Some institutions, like banks and certain agencies of government, have started using quantum cryptography to ensure that data transmitted through their networks are secure.
How it Works
Encryption is the securing of data transmitted from a source. There are many ways to do this, ranging from a simple code to a complex mechanical device to computer codes.
In essence, encryption is used to make a message unreadable by anyone without a key. Let’s say that Alex has a message for Bob.
APPLES ARE SWEET.
To encrypt this message, Alex needs a key to translate this into what looks like gibberish. To illustrate the point, let’s use a simple encryption key: A becomes B, B becomes C, and so on. The encoded message should look like this.
BQQMFT BSF TXFFU.
The encrypted message now looks like gibberish. Bob then needs the key, and use it in reverse to read the message.
Messages sent through encryption can be as simple as this. A more likely scenario for using encryption in our daily routines is the usage of the Internet, with all the usernames, passwords, credit card information, and a plethora of other personal information.
Historically, all encryption was done either mechanically or mathematically. This means that with enough time and the proper resources, most simple encryption is crackable. This is very applicable today, where computers can simply try to use every possible combination to find the key. So to help prevent this, several security systems based on mathematical ideas were developed, and are still used now. Essentially, two keys are used by a computer: a public key that everyone can access, and a public key that only the computer knows. These methods are collectively known as asymmetric encryption.
There is still a problem with this. Anyone that somehow gets both keys can theoretically steal the data without you being the wiser.
The Basic Physics
This is where quantum physics comes in. The key idea that applies in data security here is Heisenberg’s uncertainty principle, which states that for any particle, both its velocity (more accurately, momentum) and position cannot be known with 100% certainty at any particular time. This is due to the fact that everything exhibits wave-like and particle-like behaviour at all times. This is more apparent with molecules, atoms, and anything smaller; the tinier the particle, the more wave-like it is.
Well, that’s how most physics sources explain it anyway, but it’s a little difficult to imagine. Here’s another way of looking at the uncertainty principle. Let’s look at an electron, which is a very tiny particle. So tiny, it can be affected heavily by quantum mechanics.
Let’s keep our electron in the dark, literally. Just the electron in space, moving about. Let’s pretend that we, as the observers, do not affect the electron in any way.
If we assume that the electron’s velocity is known with 100% accuracy, then there is no way we can know where it is. It’s like saying, “Our car is going at 100 km/h, but I don’t know where my driver took it now.” Same thing with the electron: since we only know how fast it is going, we may be able to calculate where it is (using classical physics that does not work in the quantum world), but we still cannot be 100% sure that it is there at that time.
To know for certain where the electron is, we need to look at it. To do so, we need to shine some light on the subject. Most of us know light as a wave (an electromagnetic wave, to be precise). But since light moves very fast and has a small wavelength, we can also consider this to be a particle, called a photon.
The difficulty now is that when we observe something, a photon has to come from that something to our eyes. So for us to actually know where the electron is, a photon coming off an electron has to be sensed. In order to do that, either a photon has to come directly from the electron, or has to bounce off the electron.
We know that when two things bounce off each other, their new motion paths are different from the old ones. And as with regular collisions, an electron and a photon bouncing off each other will change each other’s momentum. So we may now be able to “see” the electron, we cannot know where it is now headed. Furthermore, the diagram shows that we know where the photon is coming from. But in practice, we never know where exactly the photon comes from.
And finally, the time that passes by between the collision and the observation will also come into effect. The more time between the collision and the observation, the more uncertain we are of both the position and momentum of the electron, since the electron can still collide with other photons. This all adds up, and therefore the electron’s state of motion has now changed.
In summary, the mere act of observing anything on the quantum level changes the information associated with it. So how does this link to data security?
Application
Quantum cryptography is still based on the same mathematical principles behind asymmetric encryption. The additional security we get from this stems from the fact that observation changes the state of the data.
Let’s look at two scenarios with quantum cryptography. In the first scenario, no data is stolen. In the second, data was stolen.
Scenario 1: No data taken
- Data is transmitted.
- No outside observer, so no change in quantum state of keys.
- Everything’s A-OK!
Scenario 2: Data was stolen
- Data is transmitted,
- Thief has to observe data. Quantum states of data change due to observation. Thief has unreadable data due to changes in quantum states.
Here’s an infographic on how this works, in more detail.
A graphical explanation of quantum encryption.
It would be helpful to think of the polarisation of each photon as the quantum states. In fact, it is one of the quantum states we are talking about. As seen with Eve the eavesdropper, an attempt to intercept the message with the wrong decoder changes the quantum state of the data, making it unreadable.
That, dear readers, is how physics is related to your online security. In the future, we’ll see what we can come up with
Sources
- http://phys.org/news/2013-04-physicists-successfully-transmit-quantum-code.html
- http://en.wikipedia.org/wiki/Quantum_cryptography
- http://www.howstuffworks.com/encryption.htm
- http://www.computerhope.com/jargon/b/brutforc.htm
- http://www.webopedia.com/TERM/P/public_key_cryptography.html
- http://www.scientificamerican.com/media/inline/000479CD-F58C-11BE-AD0683414B7F0000_quantum.gif
Quantum Mechanics and (Future) Internet Security
