Quantum & post-quantum cryptography
‘Q-day’ is closer than we want to believe
Editor’s insight
Quantum computing has spent years sitting just over the cybersecurity horizon. But prepared organizations are not waiting for a cryptographically relevant quantum computer before taking the risk seriously.
Attackers can steal encrypted data today and hold onto it until quantum computers are powerful enough to break the encryption. Known as “harvest now, decrypt later,” the threat is greatest for sensitive data that may still have value years from now, including government information, intellectual property, and critical infrastructure data.
The 2026 Thales Data Threat Report: Quantum & AI Trends found 61% of respondents considered harvest now, decrypt later their leading quantum concern. Almost six in ten said prototyping and evaluating post-quantum cryptographic algorithms was their leading route towards becoming quantum safe.
Europe puts a date on migration
The transition is already moving onto regulatory and security roadmaps. The EU’s coordinated roadmap calls for Member States to start moving to post-quantum cryptography by the end of 2026. High-risk use cases should transition as soon as possible and no later than the end of 2030.
For businesses, that brings a more immediate problem into view: finding all the cryptography they may eventually have to replace.
Public-key cryptography is buried throughout modern infrastructure. It protects certificates and authentication systems, secures communications between applications, and appears across networks, connected devices, and third-party services. Some of those systems will still be running well into the next decade. Others may depend on cryptographic components that are difficult to identify or replace.
Cache the hash
Before anything can be replaced, businesses need to know where vulnerable cryptography is being used. That means finding the algorithms, keys, certificates, and hashes already protecting their systems and data, especially information that will still be sensitive years from now.
They also need to know what will happen when an algorithm has to change. Systems built around crypto-agility can accommodate new cryptographic standards without requiring the surrounding infrastructure to be rebuilt. Hybrid approaches offer another route, allowing conventional and post-quantum cryptography to operate together while new implementations are tested.
Nobody knows the exact date when a quantum computer will be capable of breaking the public-key cryptography businesses use today. Waiting for that date leaves very little room to deal with cryptography embedded across years of infrastructure. The work begins much earlier.
Top trends
Cryptographic inventories move up the agenda: Before businesses can plan a PQC migration, they have to find the vulnerable algorithms, keys, certificates, and dependencies already spread across their environments.
Crypto-agility gets a practical test: Moving to PQC will expose systems where changing an algorithm or certificate means substantial redevelopment. Businesses are starting to look at whether their infrastructure can accommodate cryptographic changes without major disruption.
Long-lived data goes first: Data that needs to stay confidential for years is already exposed to harvest-now-decrypt-later attacks. Its useful lifespan can help businesses decide which systems and information should be prioritized for migration.
Regulatory watch: EU post-quantum cryptography roadmap
In September, the European Commission published feedback and FAQs on its coordinated PQC roadmap. The guidance gives organizations more detail on the expected timetable for migration and the role of hybrid cryptography. Spain’s CCN, meanwhile, is calling for quantum-resistant cryptography to be in place by 2030 or 2035, depending on how critical the system is.
CISO voice
“In my meetings with security leaders all over the world, I’ve had many discussions about their post-Quantum plans. The one impression I’ve been left with is that CISOs and CIOs seem to believe they will get plenty of warning before the so-called ‘Q-Day’, and that they will be able to fit the transition process into a budgetary process. This belief is fundamentally misguided. If a Cryptographically Relevant Quantum Computer (CRQC) is developed, it will likely happen inside the intelligence agencies of a leading country. It won’t be a public event, and its development will be kept secret and tightly controlled. As soon as the announcement happened, every single target would prioritize the transition to post-quantum algorithms, and the hundreds of millions of dollars invested in that quantum computer would be wasted. Instead, these agencies will use the quantum computer secretly, and very carefully indeed. They will choose their targets cautiously, likely starting with the private keys used by intermediate certificate authorities, allowing them to undetectably forget any certificate needed.”
— Ian Farquhar (ex Security Chief Technology Officer at Gigamon, waiting for new designation)
Innovation spotlight
Barcelona-based Quside develops quantum random number generators that can be used in encryption and other security systems. In 2026, it partnered with IKERLAN to test the technology in systems that banks, telecoms providers, transport operators, and critical infrastructure use.
Barcelona Cybersecurity Congress update
This year’s Barcelona Cybersecurity Congress will examine how organizations are preparing for the security implications of quantum computing. The move to post-quantum cryptography will bring questions around crypto-agility, long-lived sensitive data, and how businesses replace vulnerable cryptography already embedded across their systems into focus at the conference.
Barcelona Cybersecurity Congress 2026
Dates: 3–5 November
Location: Barcelona
Co-located with: Smart City Expo World Congress
CONNECTING EUROPE’S CYBERSECURITY ECOSYSTEM
Register here for Barcelona Cybersecurity Congress 2026!