Quantum Key Distribution : Basics and status in India – UPSC GS3

Context: A joint team of scientists from Defence Research and Development Organisation (DRDO) and Indian Institute of Technology (IIT) Delhi, for the first time in the country successfully demonstrated Quantum Key Distribution link between Prayagraj and Vindhyachal in Uttar Pradesh, a distance of more than 100 kilometres.


What is Quantum Key Distribution Technology?
  • QKD, also called Quantum Cryptography, is a mechanism to develop secure communication.
  • It provides a way of distributing and sharing secret keys that are necessary for cryptographic protocols.
  • Cryptography is the study of secure communications techniques that allow only the sender and intended recipient of a message to view its contents.
  • Cryptographic algorithms and protocols are necessary to keep a system secure, particularly when communicating through an untrusted network such as the Internet.
  • The conventional cryptosystems used for data-encryption rely on the complexity of mathematical algorithms, whereas the security offered by quantum communication is based on the laws of Physics.
What are the two main categories of QKD?
  • Prepare-and-Measure Protocols:
    • It focuses on measuring unknown quantum states. This type of protocol can be used to detect eavesdropping (spying), as well as how much data was potentially intercepted.
  • Entanglement-based Protocols:
    • It focuses on quantum states in which two objects are linked together, forming a combined quantum state.
    • The concept of entanglement means that measurement of one object thereby affects the other. In this method, if an eavesdropper accesses a previously trusted node and changes something, the other involved parties will know.
How does the Quantum Key Distribution Work?
  • In the QKD, encryption keys are sent as ‘qubits’ (or quantum bits) in an optical fibre.
  • Qubits : is the equivalent of bits in a binary system.
  • Optical fibres are capable of transmitting more data over longer distances and faster than other mediums. It works on the principle of total internal Reflections.
  • QKD implementation requires interactions between the legitimate users. These interactions need to be authenticated. This can be achieved through various cryptographic means.
  • QKD allows two distant users, who do not share a long secret key initially, to produce a common, random string of secret bits, called a secret key.
  • The end-result is that QKD can utilize an authenticated communication channel and transform it into a secure communication channel.
  • It is designed in a way that if an illegitimate entity tries to read the transmission, it will disturb the qubits – which are encoded on photons.
  • This will generate transmission errors, leading to legitimate end-users being immediately informed.

Why is QKD needed?
  • QKD is essential to address the threat that rapid advancement in Quantum Computing poses to the security of the data being transported by various critical sectors through the current communication networks.
  • Quantum Technologies can broadly be divided into four verticals viz. Quantum Computing, Quantum Communications, Quantum Sensors and Quantum Materials.
  • The technology would be useful in enabling various start-ups and small and medium enterprises in the domain of quantum information.
  • It will enable security agencies to plan a suitable quantum communication network with indigenous technology backbone.
  • The encryption is unbreakable and that’s mainly because of the way data is carried via the photon.
  • A photon cannot be perfectly copied and any attempt to measure it will disturb it. This means that a person trying to intercept the data will leave a trace.
What are the challenges associated with the QKD?
  • Integration of QKD Systems into Current Infrastructure:
    • For now, it is currently difficult to implement an ideal infrastructure for QKD.
    • QKD is perfectly secure in theory, but in practice, imperfections in tools like single photon detectors create many security vulnerabilities.
  • Distance in which photons can travel:
    • Modern fiber optic cables are typically limited in how far they can carry a photon. Commonly, this range is seen to be upward of 100 km.
Use of QKD:
  • QKD relies on already having a classically authenticated channel of communications established.
  • This means that one of the participating users has probably already exchanged a symmetric key in the first place, creating a sufficient level of security.
  • A system can already be made sufficiently secure without QKD through using another advanced encryption standard.
  • However, as the use of quantum computers becomes more frequent, the possibility that an attacker could utilize quantum computing’s ability to crack into current encryption methods rises, making QKD more relevant.
Way Forward:
  • The power of start-ups and Big Tech corporations involved in developing quantum technology and applications must be harnessed.
  • The focus should be to develop an overarching strategy for the next 10-15 years. The strategy must ensure that there is no misallocation of resources and that the efforts put in are concentrated in key areas that provide both economic and strategic benefits.
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