According to estimates from 2025, breaking a commonly used RSA key would require a machine with on the order of a million qubits. The report explains that while NISQ (Noisy Intermediate-Scale Quantum) computers, ranging from a few hundred to a few thousand qubits, are limited by “noise” and short calculation windows, combining multiple physical qubits into one logical qubit is essential for error correction.

This means current machines do not pose an immediate threat, but achieving truly secure quantum computing requires significant hurdles to be overcome. The vulnerability stems from the potential for a quantum computer to rapidly factor large numbers, a task that underpins the security of RSA, developed in 1977 by Rivest, Shamir and Adleman.

NISQ Era Limitations and the Threshold of Quantum Threat

This calculation, detailed in a recent report, indicates that current quantum computers pose no immediate danger, but achieving truly secure quantum computing presents a substantial hurdle. John Preskill coined the term “NISQ (Noisy Intermediate-Scale Quantum)” in 2018 to describe the current era of quantum computing, highlighting that these machines are limited by “noise” and can only perform short calculations before errors occur. This means the number of usable, stable qubits is far lower than the total qubit count, extending the timeline for a viable cryptographic threat. “Pomnożenie dwóch dużych liczb pierwszych jest łatwe, ale odgadnięcie, z jakich liczb pierwszych powstał wynik, jest przy odpowiednio dużych liczbach praktycznie niemożliwe,” the report states, outlining the mathematical foundation of RSA security. The potential for “Harvest Now, Decrypt Later” attacks, collecting encrypted data for decryption when quantum computers mature, is a particularly pressing concern.

Experts participating in the “Quantum Threat Timeline Report” estimate a probability exceeding 70% that a quantum computer capable of breaking RSA-2048 within 48 hours will exist within 15 years, with eight experts placing that probability above 95%. This assessment is based on expert opinion, not a prediction of specific hardware development. The report emphasizes that migration to post-quantum cryptography isn’t simply about selecting an algorithm, but about organizational inventory and designing systems that allow for algorithm replacement without complete overhauls. “Z kryptografią postkwantową będzie podobnie, tylko że skutki mogą być mniej widoczne,” the report concludes, suggesting proactive preparation is important.

Według ekspertów biorących udział w badaniach “Quantum Threat Timeline Report”, 17 z 29 specjalistów uważa, że komputer kwantowy zdolny łamać RSA-2048 w ciągu 48 godzin powstanie w ciągu 15 lat i jest to “prawdopodobne” (>70%) a 8 ekspertów twierdzi, że szanse przekraczają 95%.

The current limitations of noisy intermediate-scale quantum (NISQ) devices necessitate a multi-pronged approach to cryptographic security, as practical error correction demands combining multiple physical qubits into a single, stable logical qubit. This complexity extends the timeline for building a fault-tolerant quantum computer capable of breaking current encryption standards, but does not eliminate the long-term threat. John Preskill introduced the term NISQ in 2018 to define this era, acknowledging that these machines are hampered by inherent “noise” limiting calculation length before errors accumulate. This assessment, based on the opinions of 17 of 29 specialists, highlights the urgency of transitioning to post-quantum cryptography. Eight experts even place the probability of such a machine appearing within that timeframe exceeding 95%. Migration to post-quantum cryptography is a widespread implementation across countless systems. The report emphasizes that the process will mirror previous cryptographic shifts, but with potentially less visible consequences. The challenge lies in proactively replacing existing algorithms before a sufficiently powerful quantum computer materializes, safeguarding data against potential decryption through “Harvest Now, Decrypt Later” attacks.

Peter Shor’s Algorithm and the Risk of “Harvest Now, Decrypt Later” Attacks

This timeline highlights the urgency surrounding the transition to post-quantum cryptography, a shift that extends beyond simple algorithm selection to encompass widespread implementation across existing systems. The danger isn’t solely a future event, however, as the concept of “Harvest Now, Decrypt Later” introduces an immediate risk; adversaries are actively collecting encrypted data with the intention of decrypting it once sufficiently powerful quantum computers become available. This potential for retroactive decryption complicates the security landscape, as even data currently considered safe could be compromised in the coming years. The vulnerability stems from Peter Shor’s 1994 algorithm, which provides a method for efficiently factoring the large numbers that underpin RSA encryption, a forged key, to unlock previously secure communications. While current noisy intermediate-scale quantum (NISQ) devices are not yet capable of executing Shor’s algorithm at scale, the threat is not theoretical, and the timeframe for a capable machine is shrinking. Organizations must first inventory their use of cryptography, identify the most sensitive data requiring long-term protection, and establish clear lines of responsibility.

Post-Quantum Cryptography Standards and EU Migration Recommendations

Seventeen out of twenty-nine specialists surveyed believe such a machine will emerge within fifteen years, classifying the possibility as probable. PQC algorithms, unlike their predecessors, do not rely on mathematical problems susceptible to efficient solutions by quantum computers, instead using concepts like lattices and hash functions. This approach allows for secure communication using conventional computing infrastructure, eliminating the need for quantum hardware to maintain data protection. The Institute’s report highlights that PQC is standard software operating on these devices, based on different mathematical problems than RSA. The Institute notes that an owner of such a machine benefits most while its existence remains secret, making covert data retrieval a viable strategy. Michał Szaniewski writes, “Właściciel takiej maszyny najwięcej zyskuje, dopóki jej istnienie pozostaje tajemnicą.”

Source: https://aiqlab.pl/aktualnosci/artykuly/post-quantum-cryptography-czy-twoje-dane-sa-bezpieczne/

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