The threat centers on the eventual capability of quantum computers to break widely used public-key cryptographic algorithms such as RSA, ECC, and DSA, which underpin secure communications, digital signatures, and data confidentiality in many industries, notably finance. Quantum algorithms like Shor's algorithm can efficiently factor large integers and compute discrete logarithms, rendering current asymmetric encryption vulnerable. Although building sufficiently powerful and stable quantum computers remains a significant technical challenge, estimates suggest such machines could be operational within 10 to 20 years. This timeline urges organizations to start preparing now, as encrypted data intercepted today could be decrypted in the future once quantum computers become available, a concept known as 'harvest now, decrypt later.' The threat does not involve an immediate exploit but represents a strategic vulnerability that could compromise the confidentiality and integrity of sensitive information. The transition to quantum-resistant cryptography (post-quantum cryptography) involves adopting new algorithms designed to withstand quantum attacks, such as lattice-based, hash-based, or code-based cryptography. The lack of patches or immediate exploits highlights the forward-looking nature of this threat. Organizations must inventory cryptographic assets, evaluate quantum-safe alternatives, and develop migration strategies to maintain long-term security.

For European organizations, particularly in the financial sector, the emergence of quantum computers capable of breaking current public-key encryption could lead to severe breaches of confidentiality, exposing sensitive financial data, personal information, and intellectual property. This would undermine trust in digital transactions and could disrupt critical financial infrastructure. Other industries reliant on secure communications and data integrity, such as healthcare, government, and telecommunications, would also face significant risks. The potential for 'harvest now, decrypt later' attacks means that data intercepted today could be decrypted in the future, increasing the urgency for proactive measures. The impact extends beyond data confidentiality to include potential fraud, identity theft, and disruption of services. Regulatory compliance frameworks in Europe, such as GDPR, would necessitate stringent data protection measures, making preparedness essential to avoid legal and reputational consequences.

European organizations should begin by conducting comprehensive audits of their cryptographic assets to identify where vulnerable public-key algorithms are in use. They should monitor developments in post-quantum cryptography standards, such as those being developed by NIST, and plan phased adoption of quantum-resistant algorithms. Implementing hybrid cryptographic solutions that combine classical and post-quantum algorithms can provide transitional security. Organizations should also invest in staff training to raise awareness of quantum threats and update incident response plans to consider quantum-related risks. Collaboration with industry groups and regulators will help align strategies and share best practices. Additionally, securing data at rest and in transit with strong symmetric encryption and robust key management remains critical, as symmetric algorithms are less vulnerable to quantum attacks but may require longer keys. Finally, organizations should track advancements in quantum computing capabilities to adjust their mitigation timelines accordingly.