Future quantum attacks on blockchains might be countered through Post-Quantum Cryptography (PQC), yet quantum communication utilizes a distinct method known as Quantum Key Distribution (QKD). This approach relies on the laws of physics rather than computational strength. The technology is transitioning from laboratory settings to real-world applications.
This article explores the protections offered by QKD, identifies existing vulnerabilities, and discusses why a "hack-proof internet" remains more of a promise than a reality.
Brief Overview
While QKD is fundamentally based on physical laws, its protective capabilities are limited to the key distribution process, not the entire communication system. Vulnerabilities still exist in end-user devices, protocol implementation errors, and human factors. Nonetheless, QKD technology has advanced beyond experimental phases. For instance, China launched the Micius satellite, established extensive ground networks, and is offering commercial services, while Europe is actively developing its own quantum infrastructure.
Understanding QKD
The core principle of QKD is based on a fundamental tenet of quantum mechanics: an attempt to measure an unknown quantum state typically causes perturbation, which manifests as increased errors and can indicate interference. This allows for the detection of eavesdropping during checks and the option to disregard compromised keys.
This distinction sets QKD apart from post-quantum cryptography; while the reliability of PQC hinges on the computational complexity of mathematical problems, the security of QKD in an ideal scenario is grounded in physics. The BB84 protocol, introduced in 1984, remains a cornerstone of practical systems, yet it also presents a vulnerability: the "ideal model" does not equate to the actual hardware and implementation, which can be susceptible to weaknesses.
The Micius satellite was launched by China in 2016. In 2017, it successfully demonstrated QKD between a satellite and ground station over a distance of 1,200 kilometers, and in 2018, it facilitated intercontinental key exchanges between China and Austria, enabling secure video communication between Beijing and Vienna through a trusted satellite relay.
Experiments indicate that quantum signals can coexist with conventional internet traffic within existing fiber optic cables. In July 2026, a team from Northwestern University (Illinois, USA) successfully transmitted entangled photons through standard fiber optics while simultaneously handling regular internet traffic.
The fundamental challenge lies in the fact that quantum signals are encoded in single photons, while classical optics transmit millions of light particles through the same fiber, making even minor disturbances capable of disrupting delicate entanglement. Successfully separating quantum and classical data within a single cable, ensuring that classical signals do not overwhelm quantum ones, eliminates a significant barrier to widespread adoption of the technology.
Simultaneously, researchers from NYU, Qunnect, and Cisco showcased a functioning urban quantum network in New York City. In 2023, they connected Brooklyn and Manhattan through a quantum channel over a conventional line, and in a new experiment, a third node was added to form a star network. This network included two sources of entangled photons at the Brooklyn startup Qunnect and a hub in the commercial data center QTD in Manhattan, achieving polarization entanglement exchange at a rate exceeding 1.5 events per second across the city.
However, achieving one and a half entanglement exchanges per second within a single city is still far from a fully operational service. The realization of a quantum internet that transmits information through quantum networks to end-user devices is still a distant goal. Nevertheless, the trajectory is clear: the technology is evolving from pure physics into the engineering of urban networks.
While the laws of physics safeguard the principle of quantum key distribution, potential attack vectors remain. For instance, researcher Alexander Miller noted in a preprint that due to synchronization issues with the onboard lasers of Micius, an attacker could theoretically distinguish genuine signals from specific "decoy" signals used by the system to verify channel security. According to his calculations, the accuracy of such discrimination could reach 98.7%.
This is not an isolated incident; similar vulnerabilities in QKD transmitters have been identified by other research teams. Thus, the practical security of such systems depends not only on the protocol's properties but also on the quality of the equipment, and currently, there are numerous limitations in this area.
Implications
While QKD is not yet ready for mass market deployment, it is in high demand for securing communications at the national level. Consequently, government contracts remain the primary source of funding. However, the distribution of resources is uneven. According to McKinsey, approximately 90% of investments in quantum startups in 2025 will be directed not towards engineering solutions and communications, but rather towards quantum computing.
It is also important to note that not all experts consider QKD to be the optimal solution. For example, the NSA and NCSC do not recommend employing this technology for safeguarding government and military communications. They argue that QKD does not address authentication issues, necessitates separate fiber optic infrastructure and specialized equipment, operates over limited distances, relies on so-called "trusted nodes," and is vulnerable to basic signal jamming. Therefore, both organizations favor post-quantum cryptography. This suggests that the concept of a "quantum internet" is currently viewed not as the sole path to secure communication, but rather as one of several competing strategies.
Government investments in quantum technologies are expected to reach $56.7 billion by 2025, but authorities are not merely funding research. They are beginning to establish rules for export, protection, and standardization.
Q-check ForkLog: Quantum Communications
Is there revenue?Limited — government contracts, pilot projects, and initial commercial services, with no mass market yet.
Is it a prototype or a product?Operational networks exist along with commercial launches, but it remains a costly niche infrastructure.
Is there a roadmap or a press release?Government projects have tangible deployments with results.
Who is paying?Primarily the government: this is a matter of sovereignty and national security.
What can be verified now?Published experiments (Micius), preprints on vulnerabilities, and operational communication lines.