Quantum Cryptography

What Is Quantum Cryptography?

Quantum cryptography is an encryption approach that leverages the naturally occurring features of quantum physics to safeguard and transmit data in an unhackable manner. Cryptography is the technique of encrypting and safeguarding data such that it can only be decrypted by the person who possesses the correct secret key. 

Quantum cryptography differs from standard cryptographic systems in that it bases its security model on physics rather than mathematics. Quantum cryptography is a perfectly secure system that cannot be penetrated without the awareness of the message sender or receiver. That is, copying or seeing data encoded in a quantum state without warning the transmitter or receiver is impossible.

Working Mechanism of Quantum Cryptography 

Theoretically, quantum cryptography operates based on a model published in 1984. The model assumes two users named Jane and Robert want to send a message securely. Jane starts the conversation by sending Robert a key. A streamlet of photons traveling in one direction is the key. 

Each photon is associated with a single bit of data, either a 0 or a 1. However, these photons oscillate or vibrate in addition to their linear motion. As a result, the photons pass through a polarizer before Jane, the sender, begins the transmission. 

A polarizer is a filter that allows certain photons to travel through with the same vibrations while allowing others to pass through in a different state of vibration. Vertical (1 bit), horizontal (0 bit), 45 degrees right (1 bit), or 45 degrees left could be the polarized states (0 bit). 

Whatever technique she employs, the broadcast has one of two polarizations indicating a single bit, either 0 or 1. Photons are now traveling via optical fiber from the polarizer to Robert's receiver. A beam splitter is used in this technique to read the polarization of every photon. 

Robert does not recognize the correct polarization of the photons when he receives the photon key; thus, one polarization is picked randomly. Jane now compares the polarizers Robert used to polarize the key and tells Robert the polarizer she used to send every photon. Robert then confirms whether or not he used the correct polarizer. 

The photons read with the incorrect splitter are then deleted, and the leftover sequence is thought to be the key. Assume there is an eavesdropper around; let's call her Carol. Carol tries to listen in using the same tools as Robert. 

On the other hand, Robert has the advantage of conversing with Jane to verify which polarizer type was utilized for every photon, whereas Carol does not. Carol ends up erroneously rendering the final key. Robert and Jane would also be aware if Carol was listening in on them. Carol's observations of the photon flow would alter the photon positions that Robert and Jane anticipate seeing.