The history, definition, How does QKD Work, types, difficulties, and future of QKD will all be covered in this blog.
History of QKD
Stephen Wiesner of Columbia University first proposed quantum cryptography in the 1970s with the concept of quantum conjugate coding, which is where QKD got its start. In 1983, Wiesner’s paper was released. Later, Charles H. Bennett developed the idea of secure communication, drawing inspiration from Wiesner’s research. Bennett created the first quantum cryptography technique, BB84, using nonorthogonal states. Artur Ekert’s 1990 quantum entanglement-based theory offered an alternative to QKD.
What is QKD?
Quantum key distribution (QKD) is a secure method for sharing encryption keys hidden from others. It exchanges cryptographic keys in a method that is provable and ensures security by utilising features found in quantum physics.
Two people can create and exchange a key that is used to encrypt and decrypt messages to QKD. In particular, QKD is how the key is shared between the parties.
Conventional key distribution relies on public key cyphers, which employ intricate mathematical computations that are impossible to crack without an excessive amount of computer power. However, a number of problems threaten the sustainability of public key cyphers, including the ongoing adoption of new attack techniques, shoddy random number generators, and overall increases in processing power. Furthermore, the majority of current public key encryption techniques will become dangerous due to quantum computing.
Because QKD employs a quantum system that protects the data using fundamental rules of nature rather than mathematics, it differs from conventional key distribution. For instance, attackers cannot simply replicate the data in the same way that they may copy network traffic today since the no-cloning theorem asserts that it is impossible to produce identical copies of an unknown quantum state. Furthermore, the system will alter so that the intended parties are aware if an attacker tampers with it or looks at it. Increased processing power won’t affect this process in any way.
How does QKD Work?
In order for QKD to function, numerous light particles, or photons, must be sent between parties over fibre optic cables. Together, the delivered photons form a stream of ones and zeros, with each photon having a unique quantum state. Qubits, the binary system’s counterpart of bits, are this stream of ones and zeros. After passing through a beam splitter on its way to the receiving end, a photon is forced to choose a path at random and enter a photon collector. The sender then checks the data from the receiver, which would have sent each photon, with the information from the original sender about the photon sequence.
In the incorrect beam collector, photons are destroyed, leaving behind a certain bit sequence. Data can then be encrypted using this bit sequence as a key. Error repair and other post-processing procedures eliminate any mistakes and data leaks. Another post-processing step that eliminates whatever information an eavesdropper might have learnt about the final secret key is delayed privacy amplification.
Types of QKD
Although there are numerous varieties of QKD, prepare-and-measure protocols and entanglement-based protocols are the two primary kinds.
- Prepare-and-measure techniques measure unnamed quantum states. They can be used to identify instances of eavesdropping and determine the amount of data that may have been captured.
- Quantum states in which two items are connected to form a combined quantum state are the main focus of entanglement-based protocols. According to the theory of entanglement, measuring one thing has an impact on another. The other parties involved will be aware if an eavesdropper gains access to a previously trusted node and makes changes.
Just attempting to view the photons alters the system when quantum entanglement or quantum superpositions are used, making an intrusion detectable.
Discrete variable QKD (DV-QKD) and continuous variable QKD (CV-QKD) are two additional, more specialised forms of QKD.
- In order to measure quantum states, DV-QKD uses a photon detector to encode quantum information in variables. The BB84 protocol is an illustration of a DV-QKD protocol.
- CV-QKD transmits light to a receiver by encoding quantum information on the laser’s amplitude and phase quadrants. This approach is used in the Silber horn protocol.
Here are a few instances of QKD protocols:
- BB84
- Silberhorn
- Decoy state
- KMB09
- E91
Challenges of QKD
The three main issues facing QKD are as follows:
- The distance that photons can travel.
- The incorporation of QKD systems into existing infrastructure; and the initial application of QKD.
- Setting up the perfect infrastructure for QKD is challenging.
Although it is completely safe in theory, security flaws in instruments like single photon detectors make it vulnerable in practice. Keeping security analysis in mind is crucial.
The distance that a photon can travel through modern fibre optic connections is usually restricted. Frequently, the range exceeds 100 km. In order to apply QKD, several organizations and groups have been able to expand this range. For instance, Corning Inc. and the University of Geneva collaborated to build a system that, in perfect circumstances, could transport a photon 307 km. In the United States, Quantum Xchange introduced Phio, a QKD network that uses a patent-pending, out-of-band delivery method called Phio Trusted Xchange to distribute quantum keys over an apparently infinite distance.
The fact that QKD depends on the establishment of a classically authenticated communication channel presents another difficulty. This indicates that a sufficient level of security was established as one of the people involved had previously exchanged a symmetric key. Without QKD, a system can already be adequately safe by utilising another cutting-edge encryption method. However, the likelihood that an attacker may utilize quantum computing to break existing encryption techniques increases with the introduction of quantum computers, which makes QKD increasingly pertinent.
Future of QKD
The Cloud Security Alliance (CSA) established the Quantum-Safe Security Working Group (QSSWG) to encourage the uptake of novel technologies that facilitate the steady use of quantum computing. To enhance high data rates and raise the total effective distance of QKD, new technology is being developed. With new networks and businesses providing commercial QKD systems, QKD is starting to be utilized more extensively in a business context.
