# How Vulnerable is Online Privacy to Quantum Computers?

## Quantum computing is on the rise, which means your online privacy is at risk. Learn how quantum computing can affect your data protection in this guide!

A team of researchers has announced a new approach that has the potential, in theory, to utilize a basic quantum computer to bypass the most prevalent digital privacy protection technique.

According to the research team, while the technology was successfully demonstrated on a small scale, other experts were skeptical about its ability to outperform a regular computer when expanded. The publication, which was released last month on the arXiv preprint server, serves as a warning of the vulnerability of online privacy.

Although quantum computers have the potential to threaten current encryption systems, they are still in the early stages of development. It is widely believed that it will take many years before quantum computers can break encryption keys faster than conventional computers. An encryption key is a string of characters used in an encryption algorithm to secure data.

In the 1990s, researchers discovered that quantum computers could leverage the unique properties of physics to perform tasks that are beyond the capabilities of classical computers. Mathematician Peter Shor, who is now at the Massachusetts Institute of Technology, demonstrated in 1994 how quantum superposition (which allows atomic-scale objects to exist in multiple states simultaneously) and quantum interference (similar to the interactions between waves in water) could be used to decompose integers into prime numbers. Prime numbers are integers that cannot be further divided into integers without leaving remainders.

The current encryption technology used for securing network privacy and security is vulnerable to quantum computers due to Shor's algorithm, which can crack these systems much faster than classical computers. One such encryption system based on large prime numbers is known as the Rivest–Shamir–Adleman (RSA) algorithm, named after its three inventors. However, Shor's algorithm requires a quantum computer much larger than existing prototypes. The size of a quantum computer is determined by the number of quantum bits (qubits). Researchers estimate that breaking RSA could require a million or more qubits. The largest quantum computer currently available is the Osprey chip, announced by IBM in November last year, with 433 qubits.

The Institute of Quantum Information Science in China, along with its partners, attempted to use a different approach to break RSA encryption. Instead of Shor's algorithm, they employed the Schnorr algorithm, developed by mathematician Claus Schnorr of the University of Frankfurt, Germany in the 1990s, which can also factor integers. Although the Schnorr algorithm was originally intended for classical computers, the team utilized the quantum approximate optimization algorithm (QAOA) to execute a portion of the process on quantum computers.

According to a non-peer-reviewed paper, the algorithm developed by the authors can potentially break strong RSA keys with only 372 qubits, which corresponds to numbers with over 600 decimal digits. However, the researchers cautioned that merely increasing the number of qubits is insufficient. Currently, quantum computers are susceptible to errors, making it impossible to conduct such extensive computations with precision. "Adding qubits without decreasing the error rate is not helpful," Tsinghua University physicist Long Guilu emphasized on behalf of all the authors in an email to Nature.

According to Chaoyang Lu, a quantum computing expert at the University of Science and Technology of China who was not involved in the study, running the QAOA(**Quantum Approximate Optimization Algorithm**) algorithm on such a small computer would necessitate 372 error-free qubits, which must work with 99.9999 percent accuracy. However, the state-of-the-art qubits can only achieve an accuracy of 99.9 percent.

The researchers employed a 10-qubit quantum computer to demonstrate the method, which they used to factor a relatively simple 15-digit number, 261,980,999,226,229, into two primes, 15,538,213, and 16,860,433. While the team claims this is the largest number ever factored using a quantum computer, it is still much smaller than the encryption keys employed by modern web browsers.

The authors of the non-peer-reviewed paper state that it is currently unknown whether QAOA(**Quantum Approximate Optimization Algorithm**) can factor large numbers faster than Schnorr's classical algorithm running on a laptop. They note that while Shor's algorithm can quickly crack encryption on a large quantum computer, it is unclear whether QAOA(**Quantum Approximate Optimization Algorithm**), which is an optimization-based technology, can achieve the same level of speedup on a smaller machine, and there may still be a long way to go before it can do so.

Michele Mosca, a mathematician at the University of Waterloo, has noted that QAOA(**Quantum Approximate Optimization Algorithm**) is not the first quantum algorithm capable of factoring integers with a small number of qubits. In fact, Mosca and his colleagues published such an algorithm in 2017. As a result, the researchers believe that a very large quantum computer may not be required to factor numbers.

Other researchers have also expressed concerns about the latest paper. They argue that the paper's warnings about speed only appear at the end of the paper. Quantum computing theorist Scott Aaronson from the University of Texas at Austin called it "the most misleading quantum computing paper I've seen in the past 25 years" in a blog post. Long Guilu, on behalf of all authors, stated in an email that they plan to revise the paper to move the warning section to the front. They also welcome peer review and are willing to communicate with scientists worldwide.

Despite the uncertainty surrounding Quantum Approximate Optimization Algorithm's ability to factor large numbers faster than classical algorithms, quantum computers could still eventually break encryption using Shor's algorithm. To address this potential threat, security researchers are developing post-quantum or quantum-safe encryption systems. However, there is a risk that future quantum algorithms could still defeat these systems, leading to a collapse of confidence in digital infrastructure. This would necessitate a shift from technology lifecycle management to crisis management for quantum security migration, according to Mosca. The consequences of such a scenario would be dire.

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