Quantum cryptography ad cybersecurity
Quantum cryptography is highly secure due to the method of distributing the quantum key that is used to encrypt and decrypt data. Without a public encryption key, there is no starting point for hackers to even begin to work out what the decrypting key could be. I have often seen the concept of quantum key distribution described in a similar way to the double lock protocol. Imagining there was a box containing a key that could encrypt and decrypt messages that Bob wanted to give to Alice, Bob would put his lock on the box, send it to Alice who would also put her lock on the box, then she would send it back to Bob who would take his off, and then finally Bob would send it back to Alice just with her own lock attached. In this example, the box is unlocked without having to share any key as Alice is able to unlock Bob’s box with her own lock. The issue with this s implified method is that anyone who gained access to the data transmissions could see the effects of multiplying the data by each key and by both keys which would allow them to work out each individual secret key. Quantum key distribution has a similar concept. However, not only are the keys impossible to reverse engineer, but quantum properties do not even allow eavesdroppers to read the intercepted key correctly, yet alone to copy it. For quantum encrypted messages to be sent, both the sender and receiver must have a quantum key. Quantum key distribution works over a fibre optic cable by sending randomly polarized photons which are polarized either horizontally, vertically, diagonally left or diagonally right. The photons are sent to the receiver ( Bob’s lock applied) which uses two differently polarize d detectors tomeasure each photon’s polar ization and translates this information into bits. One detects horizontal or vertical polarizations and the other detects diagonally left or right polarizations. If a horizontal/vertical detector is used and the photons’ polar ization is vertical, the output would be a 1, however, the receiver must guess randomly which detector to use for each photon. Due to the properties of quantum mechanics this means that if, for example, a diagonal detector is used for a horizontally or vertically polarized photon, there is exactly a 50% chance of the outcome being a 1 or 0. Once all the photons have been received and passed through a random detector, there will be a sequence of random bits (Alice’s lock applied). This sequence is shared with the sender together with the detector used for each photon. By looking at filters the sender used, it can then tell the receiver which detectors were incorrectly used regardless of whether the outcome was accurate or not. These bits obtained from the incorrect random detector are discarded (Bob’s lock off) and the sequence of bits remaining becomes the key. Using this quantum key, an encrypted message can now be sent through any channel to the recipient who also has the quantum key. Although the order of detectors used by the receiver can be intercepted, an eavesdropper would still have to send the polarized photons through those detectors with the correct random polarization they had at the start. The hacker would have to completely guess which filters to apply to the photons. And in the extremely unlikely chance that the hacker guessed correctly, the detectors would have to give the exact same random result when used with the incorrect polarizations. Moreover, if this hack were even attempted, the quantum property of entanglement prevents eavesdropping. If any photon was read or attempted to copy, quantum properties of the photon would change, corrupting the data and also revealing that there was an attempt to intercept the data. In conclusion, with the limit of transistors which manufacturers can squeeze onto chips in sight, large companies are investing more and more into quantum computer research. Without appropriate measures in place, the great power of quantum computers will impose serious security threats, making today’s secure encryptions obsolete. To protect data when quantum computers are commercially available, I believe that quantum key distribution will truly allow unbreakable encryptions to be used
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