Chinese quantum shock: blockchains in the face of the imminence of Q-Day

In May 2025, China has taken a major step in terms of cybersecurity by making the first voice call quantified by quantum technology over more than 1,000 km between Beijing and Hefei. This feat is based on a national network for quantum keys (QKD) covering 16 metropolises, already protecting 500 government agencies and 380 public enterprises. At the same time, China has unveiled Tianyan-504, a quantum superconductor computer with 504 qubits, accessible via the cloud and having recorded more than 12 million connections from 50 countries. These advances mark a transition from the experimental stage to an operational reality, signaling an acceleration towards the “Q-day”, the moment when quantum computers will be able to break classic cryptographs.

Decryption: Tianyan-504 and the QKD network

The Tianyan-504, equipped with the superconductive chip “Xiaohong”, represents a significant advance in the world race for quantum supremacy. With his 504 qubits, he competes with international platforms in terms of the lifespan of qubits and reading loyalty.

The QKD network of China Telecom, on the other hand, 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 leader in the field.

The quantum threat: RSA-2048 vulnerable earlier than expected

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

In addition, a study by Google Quantum AI suggests that the factorization of an RSA-2048 key could be carried out in less than a week with less than a million noisy qubits, considerably accelerating the Q-Day calendar.

This compression of the calendar accentuates the need for current security systems, including blockchains, to prepare for an imminent post-fantal era.

Blockchains on the front line: Vulnerabilities and attack scenarios

Blockchains, especially those that use RSA or ECDSA signatures, are particularly exposed to quantum threats. The attackers can adopt a “Harvest Now, Decrypt Later” strategy and collect encrypted data today to decipher them once the quantum computing power will allow it.

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

Western countermeasures: PQC standard and infrastructure initiatives

Faced with these threats, the West develops post-quantic cryptography standards (PQC) via the NIST. Projects like Ethereum also explore PQC solutions.

Among the notable initiatives, Noris Protocol offers a decentralized infrastructure incorporating post-quantic cryptography, evidence of safety proof (DPOSEC) and an artificial intelligence in swarm (SWARM AI) to create an auto-repairing safety network.

Interview with Noris Protocol: the prospects and recommendations

To better understand the issues of cybersecurity in this new post-quantic context, we interviewed the Noris Protocol team, which offers a radically different approach, based on decentralized resilience.

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

The QKD network of China Telecom represents a major turning point, going from theory to operational reality. This system is capable of securing large -scale communications, as evidenced by the first vocal communication encrypted by Quantum between Beijing and Hefei over a distance of 1,000 km, supported by Metropolitan Quantum Networks active in 16 urban centers. However, despite its impressive technological advance, this network remains centralized architecture, with critical failures. In particular, the eight central nodes of the system remain potential targets for sophisticated attacks, which represents a significant risk. Noris Protocol, for his part, advocates a decentralized approach to overcome these vulnerabilities. The idea is to avoid any concentration of control points, thus guaranteeing reinforced security, even in the face of potential threats, while ensuring maximum resilience at the scale of critical infrastructure.

• Q2: Has your estimate of the vulnerability of conventional 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, the cybersecurity classic blockchain is found on time borrowed. These platforms are already in service in commercial and government sectors, with substantial funding behind them. The question is no longer when quantum computers break current cryptography, but what archived transactions will be decrypted as a priority. Each signature and each public key exposes to permanent vulnerability.

• Q3: What do you recommend to DEFI protocols and cold wallet holders in the face of a pre-Q-Day collection of public keys?

Cryptographic updates alone are not enough. For DEFI protocols, it is vital to adopt decentralized validation architectures, such as that of Naoris Protocol, which offer a deep defense against quantum attacks. This model makes it possible to create more robust behavioral consensus than simple cryptographic mechanisms. For cold wallet holders, it is essential to avoid the reuse of addresses, as this increases vulnerability. Migration strategies must ensure that ancient signatures are not exposed. Real security will come from validation networks where thousands of nodes check user behavior, thus providing protection against quantum attacks.

China's advances in quantum technologies represent an alarm signal for global security systems. Blockchains, in particular, must evolve quickly towards resilient and post-quantic architectures to avoid critical vulnerabilities. Initiatives like that of Noris Protocol show the way for a decentralized and adaptive cybersecurity, essential in this new technological era.