The Chinese Quantum Shock: Blockchains Facing The Imminence Of Q-Day

In May 2025, China reached a major milestone in cybersecurity by making the first quantum technology encrypted voice call over more than 1,000 km between Beijing and Hefei. This feat relies on a national quantum key distribution (QKD) network covering 16 metropolises, already protecting 500 government agencies and 380 public enterprises. At the same time, China unveiled the Tianyan-504, a 504-qubit superconducting quantum computer accessible via the cloud and having recorded over 12 million connections from 50 countries. These advances mark a shift from the experimental stage to operational reality, signaling an acceleration toward the “Q-Day,” the moment when quantum computers will be able to break classical cryptographies.

Decryption: Tianyan-504 and the QKD Network

The Tianyan-504, equipped with the superconducting “Xiaohong” chip, represents a significant advance in the global race for quantum supremacy. With its 504 qubits, it competes with international platforms in terms of qubit lifetime and readout fidelity.

China Telecom’s QKD network extends over more than 1,000 km between Beijing and Hefei, integrating 16 metropolitan networks to secure government and industrial communications.

These infrastructures demonstrate China’s ability to deploy large-scale quantum solutions, strengthening its position as a leader in the field.

The Quantum Threat: RSA-2048 Vulnerable Sooner Than Expected

Traditionally, it was estimated that about 4,099 logical qubits would be required to factor an RSA-2048 key. However, recent research has reduced this number to approximately 1,730 logical qubits, bringing closer the possibility of breaking this cryptography.

Moreover, a study by Google Quantum AI suggests that factoring an RSA-2048 key could be done in under a week using fewer than one million noisy qubits, significantly accelerating the Q-Day timeline.

This compression of the timeline emphasizes the need for current security systems, including blockchains, to prepare for an imminent post-quantum era.

Blockchains on the Front Line: Vulnerabilities and Attack Scenarios

Blockchains, especially those using RSA or ECDSA signatures, are particularly exposed to quantum threats. Attackers can adopt a “harvest now, decrypt later” strategy by collecting encrypted data today to decrypt once quantum computing power permits.

Cold wallets, whose public keys are already exposed, are also vulnerable. Migration to post-quantum systems is complex and therefore requires major updates to existing infrastructures.

Western Countermeasures: PQC Standards and Infrastructure Initiatives

In response to these threats, the West is developing post-quantum cryptography (PQC) standards through NIST. Projects like Ethereum are also exploring PQC solutions.

Among notable initiatives, Naoris Protocol offers a decentralized infrastructure integrating post-quantum cryptography, a proof-of-security consensus (dPoSec), and swarm artificial intelligence (Swarm AI) to create a self-healing security mesh.

Interview with Naoris Protocol: Perspectives and Recommendations

To better understand cybersecurity challenges in this new post-quantum context, we interviewed the Naoris Protocol team, which proposes a radically different approach based on decentralized resilience.

• Q1: What is the technological scope of the QKD network over 1,000 km and the 16 interconnected metropolitan networks?

The China Telecom QKD network represents a major turning point, moving from theory to operational reality. This system can secure large-scale communications, as evidenced by the first quantum-encrypted voice communication between Beijing and Hefei over a distance of 1,000 km, supported by active quantum metropolitan networks in 16 urban centers. However, despite its impressive technological advances, this network remains a centralized architecture with critical points of failure. In particular, the system’s eight central nodes remain potential targets for sophisticated attacks, which poses a significant risk. Naoris Protocol, on its side, advocates a decentralized approach to overcome these vulnerabilities. The idea is to avoid any concentration of control points, thus ensuring enhanced security even against potential threats, while providing maximal resilience at the scale of critical infrastructures.

• Q2: Has your assessment of the vulnerability of classic blockchains changed following these announcements?

Yes, the threat is now “imminent.” With the deployment of quantum platforms such as Quantum Secret and Quantum Cloud Seal, classical blockchain cybersecurity is running on borrowed time. These platforms are already in service in commercial and governmental sectors, backed by significant funding. The question is no longer when quantum computers will break current cryptography, but which archived transactions will be decrypted first. Every signature and every public key exposes a permanent vulnerability.

• Q3: What do you advise DeFi protocols and cold wallet holders in the face of pre-Q-Day public key harvesting?

Cryptographic updates alone are not enough. For DeFi protocols, it is vital to adopt decentralized validation architectures, like that of Naoris Protocol, which offer deep defense against quantum attacks. This model enables the creation of behavioral consensus stronger than simple cryptographic mechanisms. For cold wallet holders, it is essential to avoid address reuse because it increases vulnerability. Migration strategies must ensure that old signatures are not exposed. Real security will come from validation networks where thousands of nodes verify user behavior, thereby providing protection against quantum attacks.

China’s advances in quantum technologies represent a wake-up call for global security systems. Blockchains, in particular, must rapidly evolve toward resilient, post-quantum architectures to avoid critical vulnerabilities. Initiatives like Naoris Protocol show the way toward decentralized and adaptive cybersecurity, which is essential in this new technological era.