Why the NCSC is Cautious About Quantum Key Distribution (QKD) for Government and Military Use ?

1.    Quantum Key Distribution (QKD) is often hailed as a groundbreaking technology in the world of cybersecurity. By harnessing the principles of quantum mechanics, it promises secure key distribution between two parties, immune to eavesdropping. However, despite its potential, the UK’s National Cyber Security Centre (NCSC) had explicitly denied its endorsement for government and military applications  few years back. {Source: https://www.ncsc.gov.uk/whitepaper/quantum-security-technologies}. Here's why my opine:

• Specialist Hardware Requirement: QKD relies on complex and expensive hardware, including photon detectors and optical fibers. This infrastructure is difficult to deploy and maintain, making it impractical for widespread use, especially in sensitive and large-scale applications like government and military communications.

• Lack of Digital Signatures: Unlike traditional cryptographic systems, QKD doesn’t support digital signatures, which are crucial for verifying the authenticity of messages. Without this feature, QKD cannot fully replace current security systems that ensure data integrity and authentication.

• Why doesn't QKD support digital signatures?

• Nature of QKD: QKD’s purpose is to create a shared secret key between two parties. It does not provide the functionality of encrypting data or verifying identities, which is what digital signatures do.

• Digital signatures require private keys to sign a message and verify it with a public key. While QKD can be used to securely exchange the private keys needed for traditional cryptographic schemes (e.g., for RSA or ECDSA), QKD itself is not designed to perform signing operations.

Source: https://www.ncsc.gov.uk/whitepaper/quantum-security-technologies

Integration with Traditional Systems

2.    While QKD doesn't support digital signatures directly, it can be used in conjunction with traditional cryptographic systems. For instance, after using QKD to securely share a key, the parties can use that key with a traditional system to perform tasks like encryption, decryption, or creating digital signatures.

• Limited Range and Scalability: QKD's effectiveness is limited by the distance over which it can securely transmit keys. With current technology, it only works over relatively short distances and is not easily scalable, especially for large-scale, long-range communication networks.

• Evolving Quantum Threats: While QKD is designed to withstand future quantum computer threats, quantum research is still advancing, and new vulnerabilities may emerge. Until these risks are fully understood, relying solely on QKD for critical infrastructure would be premature.

3.    In conclusion, while QKD holds promise for the future, its current limitations in hardware, functionality, and scalability make it an impractical solution for government and military use at this stage. For now, more established and reliable cryptographic methods are preferred to secure sensitive communications.