Q-Day has already begun. Are you ready? | IBM

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Q-Day has already begun. Are you ready?

In the near future, quantum computers could break the encryption schemes that protect the internet. But if hackers get your encrypted data now, then “Q-Day” is already here. Here’s how enterprises like Cloudflare and Signal are preparing.

Published 25 June 2026

By

Rina Diane Caballar

When Cloudflare began exploring quantum-safe cryptography in 2017, they didn’t have many predecessors to model. The National Institute of Standards and Technology (NIST) had just put out a call the year before requesting new algorithms that quantum computers could not break. But for Cloudflare, one of the largest content delivery networks (CDNs) on the internet, the stakes were too high to wait.

“We saw this as a foregone conclusion,” Trey Guinn, Field CTO at Cloudflare, told IBM Think in an interview this April. “About a quarter of the internet flows through us, so it’s much broader than just fixing the cryptography stacks being used inside of Cloudflare. We wanted to be able to upgrade the default cryptography used by the whole internet.”

“Q-Day is, in a sense, in the past.”

— Shohini Ghose, quantum physicist and professor at Wilfrid Laurier University

The “foregone conclusion” is known as “Q-Day”—the day a quantum computer becomes powerful enough to crack the code behind current cryptography. Well, it’s not actually a day. The good news is that Q-Day won’t be, as in some media depictions, a hacker apocalypse triggering societal collapse. It will be a years-long series of vulnerabilities, with multiple opportunities for organizations to avoid catastrophe. The bad news is that, in a way, Q-Day has already arrived.

“It’s not that Q-Day is in the future. Q-Day is, in a sense, in the past,” said Shohini Ghose, a quantum physicist and professor at Wilfrid Laurier University, in an interview with IBM Think. In other words, anything encrypted with today’s public key ciphers is at risk of being decrypted by tomorrow’s quantum computers.

Attackers are playing the long game, gathering and storing encrypted data now with the intent to decipher it once quantum capabilities mature, in a tactic known as “harvest now, decrypt later.” Nation-state actors are reportedly “data harvesting on a grand scale.” For the average business, that means “if you have very high-value data that has a very long life, then that data is at risk,” said Zygmunt Lozinski, a Senior Technical Staff Member and Quantum Ambassador at IBM focused on quantum-safe networks. Threat actors, he says, could wait years to exploit a bank’s customer records, clinical trial information for a pharmaceutical company’s new drugs, plans for an aerospace firm’s unique engine, or designs for a manufacturer’s upcoming chips.

“We have the digital equivalent of needing to change every door lock on the planet.”

— Zygmunt Lozinski, Senior Technical Staff Member and Quantum Ambassador at IBM

Ray Harishankar, an IBM Fellow who leads strategy for IBM Quantum Safe, prefers the term “steal now, forge later.” “Today’s trusted digital signatures, certificates and identity proofs could be stolen now and then forged as fake signatures when quantum computers are capable of breaking underlying encryption algorithms,” Harishankar told IBM Think in an interview. “This threatens integrity, authenticity and nonrepudiation more than privacy. That is, it attacks the trust layer itself.”

The economic impact could be dire. The global average cost of a data breach is already millions of dollars, but a quantum-enabled cyberattack could result in trillions of dollars in losses.

To counter the threat, enterprises must migrate to quantum-safe cryptography now. “We have the digital equivalent of needing to change every door lock on the planet,” Lozinski told IBM Think in an interview. “We’re going to do this by planning for it. If we plan now, we don’t have to panic later.”

What’s at risk

Quantum computers have the potential to accelerate drug discovery, design novel materials and model future energy solutions. But they’re also poised to solve the complex math problems behind most modern encryption algorithms. Experts refer to such a quantum computer as being “cryptographically relevant.”

Not all cryptography is at equal risk. For now, NIST classifies cryptographic hash functions and symmetric encryption algorithms as relatively less vulnerable to quantum attacks. Cryptographic hash functions such as SHA-256 and SHA-3 generate “digital fingerprints” that establish the authenticity and integrity of data, including digital signatures and blockchain and cryptocurrency transactions. Meanwhile, symmetric encryption algorithms, such as the oft-hailed gold standard AES-256, help protect VPNs, files stored on hard disks and other storage devices, information stored in databases, and other large amounts of enterprise data on-premises and in the cloud. (In the constantly evolving field of...