The Quantum Threat and the Transition to Quantum-Safe Cryptography

The progress of quantum technologies represents an unprecedented challenge for cybersecurity. The ability of quantum computers to break traditional cryptographic algorithms is no longer a remote prospect, but an imminent reality that requires immediate action to protect sensitive data.

The "Harvest Now, Decrypt Later" Paradox

The real danger does not lie in the moment when a quantum computer becomes powerful enough to decrypt data (the so-called "Q-day"), but in the moment when data is captured today. This "Harvest Now, Decrypt Later" approach makes classified documents, health data, and intellectual property vulnerable, where sensitivity persists for decades.

Awareness of this threat has led 18 European nations, including Italy, to sign a white paper in November 2024, recommending immediate measures to protect the most sensitive use cases with a target horizon set for 2030. The United States has also strengthened its commitment with two Executive Orders signed in June 2026 by President Donald Trump, setting specific deadlines for the migration of federal infrastructures to post-quantum cryptography.

The Grover and Shor Algorithms: The Heart of the Problem

The quantum algorithms of Grover and Shor, developed in the '90s, represent the main threat to current cryptography.

• Grover: Reduces the effectiveness of symmetric cryptography like AES, halving the effective key length. The solution is simple: double the key length from AES-128 to AES-256.
• Shor: Challenges asymmetric cryptography (RSA and elliptic curves), solving complex mathematical problems in exponentially shorter times. Increasing key length is not an effective solution.

The NIST Response and Post-Quantum Cryptography

Since 2016, the National Institute of Standards and Technology (NIST) has conducted an international process to select new algorithms resistant to quantum computers. In 2024, it published the first three official Post-Quantum Cryptography (PQC) standards, recommending the deprecation of vulnerable public-key cryptography by 2030 and its prohibition by 2035.

PQC offers a scalable solution that works on classical computers, replacing vulnerable algorithms with schemes based on mathematical problems resistant to quantum computation, such as lattice systems and error-correcting codes. However, the migration presents technical challenges, including larger key and digital signature sizes, which affect network traffic and storage requirements.

Quantum Key Distribution: Security Based on Physics

Quantum Key Distribution (QKD) represents an alternative approach that leverages the principles of quantum mechanics to distribute cryptographic keys. Its security does not depend on mathematical problems, but on physical laws, making it theoretically secure even against future quantum computers.

However, QKD has current limitations, including the need for dedicated hardware and difficulties in transmission over long distances, confining it for now to specific high-security contexts.

The Main Path: PQC and QKD in Synergy

PQC and QKD are not in competition, but complementary. The former acts on application cryptography, while the latter on key distribution. The path to quantum-safe infrastructures likely requires the combined adoption of both technologies.

The Complex Transition: Crypto-Agility and Governance

The transition to quantum-safe cryptography is not just a technical issue, but also an organizational one. Many IT infrastructures were designed in an era where cryptography was considered stable, with algorithms deeply integrated into protocols and applications.

The concept of crypto-agility indicates the ability to update cryptographic components quickly and controllably without redesigning the entire infrastructure. This requires two fundamental steps:

• Cryptographic inventory: Structured reconnaissance of keys, certificates, libraries, protocols, and authentication systems.
• Cryptographic governance: Establishing who decides on updates, who manages the keys, which standards are accepted, and the criteria for managing priorities.

Roadmap and Challenges for Italy

In June 2025, the NIS Cooperation Group published a recommended roadmap for Member States, which includes:

• National roadmaps by the end of 2026
• Protection of high-risk use cases by 2030

For Italian organizations, this means it is possible to find customized solutions, but it is essential to invest in internal skills to critically evaluate the available offers.

Critical Sectors and Differentiated Approaches

Not all sectors are equally exposed to the quantum threat, and not all require the same countermeasures. For example, the financial sector has already begun experimenting with PQC to protect critical transactions and sensitive data. On the other hand, sectors such as logistics or retail may have different priorities, unless they manage information with long sensitivity duration.

A differentiated approach is therefore fundamental. Organizations should start with a detailed analysis of their data: which are the most sensitive, how long they remain so, and which cryptographic protocols are used to protect them. Only with this information will it be possible to define an effective migration roadmap.

Collaboration and Standardization

The complexity of the quantum threat requires a coordinated response at national and international levels. In Europe, the NIS Cooperation Group has published a recommended roadmap for Member States, but each country will need to adapt these guidelines to its specific context. In Italy, collaboration between the public and private sectors will be crucial to accelerate the adoption of quantum-safe solutions.

Organizations can start participating in pilot projects, both at national and European levels, to test solutions in controlled environments. Moreover, the standardization of security practices will be essential to ensure interoperability between different systems and reduce the risks of non-uniform implementations.

Training and Awareness

One of the biggest obstacles to the transition to quantum-safe is the lack of specialized skills. The complexity of post-quantum algorithms and QKD technologies requires advanced technical training, which is currently scarcely available. Italian universities and research centers are beginning to develop dedicated programs, but the gap between demand and supply of skills remains significant.

Organizations should invest in the training of their staff, both through external courses and internal upskilling programs. Moreover, it is fundamental to promote a culture of security that includes awareness of the quantum threat at all corporate levels. Only with an integrated approach will it be possible to effectively address this challenge.

A Step-by-Step Path

The transition to quantum-safe is not a single event, but a path that requires planning, investments, and collaboration. Italian organizations should start immediately to assess their risks, identify the most critical data, and experiment with solutions on specific use cases. The road is long, but with a strategic and coordinated approach, it is possible to protect the country's digital infrastructures from one of the most complex threats of the future.