Post-Quantum Cryptography (PQC) is no longer a future option—it is an immediate security necessity. State actors are already harvesting encrypted data today with the intention of decrypting it once quantum computing reaches a breakthrough. The real urgency is not driven by the quantum computer itself, but by the time required for migration: typical migration projects take five to ten years. Organizations that do not start now are unlikely to complete the transition in time.

Why Is Today's Encryption Threatened by Quantum Computers?

The Public Key Infrastructure (PKI), which underpins a large portion of digital security, is based on mathematical problems that classical computers cannot solve within a practical timeframe: the factorization of large integers (RSA) and the discrete logarithm problem (Elliptic Curve Cryptography, ECC). A sufficiently powerful quantum computer can solve these problems in polynomial time using Shor’s algorithm.

This means that every digital signature, key exchange, VPN connection, and TLS certificate based on RSA or ECC is vulnerable to attack by a sufficiently powerful quantum computer. In addition, Grover’s algorithm weakens symmetric encryption algorithms such as AES, making the use of longer key lengths necessary.

For IT decision-makers, this means that the entire existing cryptographic infrastructure will need to be replaced over the medium term. The question is no longer if this transition will happen, but when—and how systematically it can be managed.

What Is “Harvest Now, Decrypt Later” – and Why Is the Risk Already Real Today?

The most immediate risk posed by the quantum threat already exists today. The so-called “Harvest Now, Decrypt Later” scenario describes an attack strategy that is actively being used: state actors and highly motivated attackers systematically collect encrypted data—including communications, documents, and transactions—with the intention of decrypting it once quantum computers have achieved the required level of computational power.

For organizations that handle data requiring long-term confidentiality, this risk is already material today. The following are particularly affected:

• Patents with a protection period of 20 years
• Strategic M&A Information
• Patient Data and Health Information
• Long-Term Contracts and Government Communications

All of this data may already be in the hands of actors who are simply waiting for the right moment to decrypt it.

Mosca’s Theorem provides a formal framework for quantifying this risk: if the remaining time until a cryptographically relevant quantum computer becomes available (t_quantum) plus the time required for migration (t_migrate) exceeds the required confidentiality period of the data (t_secret), immediate action is necessary. For organizations handling data that must remain confidential for 10 years or more, this threshold has already been reached today.

How Long Does a Migration to Post-Quantum Cryptography Take?

Typical PQC migration projects take between five and ten years, depending on the complexity of the IT environment. The first—and most critical—step is the creation of a cryptographic inventory: a comprehensive overview of all systems, applications, and communication channels that rely on RSA or ECC. Without this inventory, a prioritized migration is not possible. In practice, this inventory is missing in most organizations.

Both the BSI and NIST consistently recommend establishing crypto agility as a core architectural principle: designing systems in a way that allows cryptographic algorithms to be replaced without requiring a complete redesign of the underlying system architecture. This principle not only improves PQC readiness but also enhances the long-term adaptability of the entire security architecture.

Six Steps to PQC Readiness: What Do IT Decision-Makers Need to Do in Practice?

1. Create a Cryptographic Inventory – Which systems, applications, and communication channels rely on RSA or ECC?
2. Risk Prioritization – Which data assets require confidentiality for 10 years or longer?
3. Establish a PQC Readiness Task Force – Bring together stakeholders from IT, Security, Compliance, and Legal to drive the transition across the organization.
4. Embed Crypto Agility as a Core Architectural Principle – Enable cryptographic algorithms to be replaced without having to redesign or rebuild entire systems.
5. Plan Hybrid Certificates as a Transition Strategy – Ensure backward compatibility while immediately enabling protection against “Harvest Now, Decrypt Later” threats.
6. Define Vendor Requirements – Establish PQC readiness as a procurement criterion in RFPs and vendor selection processes.

Conclusion – The Urgency Does Not Come from the Quantum Computer Itself

The most common misconception in discussions about post-quantum cryptography is the assumption that organizations only need to take action once quantum computers are actually operational. The opposite is true.

The urgency is driven by the time required for migration—not by the quantum computer itself.

For data that requires long-term confidentiality, the risk posed by “Harvest Now, Decrypt Later” attacks already exists today. Organizations that start now have the opportunity to execute a structured and prioritized migration. Those that wait are unlikely to complete the transition in time—and may ultimately find themselves sitting on a vast amount of already compromised data without even realizing it.

Manage Now supports IT decision-makers in assessing their current cryptographic infrastructure and planning a structured PQC migration. Explore our Managed Security Services or speak with one of our security experts →