For decades, digital security has relied on encryption to protect bank accounts, private messages, government information and business data. Whenever people make an online payment or sign in to a secure website, cryptographic systems help keep their information away from unauthorised users.

But a new generation of computing technology could eventually challenge some of the encryption methods used today. Quantum computing, which uses principles of quantum physics to process information in fundamentally different ways, is attracting attention not only for its potential benefits but also for its implications for cybersecurity.

Although powerful quantum computers capable of breaking widely used public-key encryption at scale do not currently exist, security experts are preparing for a future in which some established cryptographic methods may no longer be sufficient.

What Is Quantum Computing?

Conventional computers process information using bits, which represent either zero or one. Quantum computers use quantum bits, known as qubits, that can exploit properties such as superposition and entanglement.

These properties allow quantum systems to approach certain problems differently from ordinary computers. They do not make quantum machines faster at every task, but they could provide significant advantages for particular mathematical and scientific problems.

Researchers are exploring applications in chemistry, materials science, optimisation and other areas. At the same time, the technology's ability to solve certain mathematical problems has important implications for digital security.

Why Could Quantum Computers Threaten Encryption?

Many widely used security systems rely on mathematical problems that are extremely difficult for conventional computers to solve at the required scale.

For example, RSA encryption and elliptic-curve cryptography are used in various digital security applications. A sufficiently powerful, fault-tolerant quantum computer running an appropriate algorithm could potentially break these systems more efficiently than a conventional computer.

This does not mean quantum computers can currently access anyone's bank account or instantly crack every password. The threat depends on the cryptographic method, the available quantum hardware and the resources needed to carry out an attack.

Symmetric encryption, such as AES, faces a different type of quantum threat and can often be strengthened by using larger key sizes.

The Hidden Risk: Steal Today, Decrypt Tomorrow

One concern is known as a harvest-now, decrypt-later attack.

In this scenario, an attacker collects encrypted information today and stores it in the hope that future technology will make it possible to decrypt the data later.

This is particularly concerning for information that must remain confidential for many years, including sensitive government communications, medical records, intellectual property and certain business secrets.

Even if the attacker cannot read the information now, the data may remain valuable long enough for future advances to matter.

For this reason, organisations handling long-lived sensitive information are being encouraged to evaluate their cryptographic systems before a large-scale quantum threat becomes practical.

What Is Post-Quantum Cryptography?

Post-quantum cryptography refers to cryptographic methods designed to remain secure against attacks from both conventional and sufficiently powerful quantum computers.

Unlike quantum communication technologies, these methods can generally run on existing computers and networks. They rely on mathematical problems believed to resist known quantum attacks.

In August 2024, the US National Institute of Standards and Technology finalised its first three principal post-quantum cryptography standards. These include ML-KEM for key establishment, ML-DSA for digital signatures and SLH-DSA for digital signatures using a different mathematical approach.

The standards provide organisations with established methods for beginning the transition away from vulnerable cryptographic systems.

Will Your Phone and Online Banking Become Unsafe?

There is no need to panic. Current online security systems remain essential, and the existence of quantum computing research does not mean everyday digital transactions are suddenly unsafe.

The challenge is preparing systems for future risks. Banks, technology companies, governments and other organisations need to identify where vulnerable cryptography is used and plan upgrades carefully.

Consumers should continue following ordinary security practices, including using strong passwords, enabling multi-factor authentication, installing software updates and avoiding suspicious links.

These measures remain important because many cyberattacks exploit stolen credentials, software vulnerabilities and human error rather than breaking encryption mathematically.

Why Replacing Encryption Is a Huge Task

Cryptography is embedded in much more than website security. It can be found in smartphones, payment systems, cloud platforms, connected vehicles, industrial equipment and digital identity systems.

Changing these systems requires more than installing a software update. Organisations must identify cryptographic dependencies, test new algorithms, check compatibility and ensure that security remains reliable during the transition.

Some devices may be difficult to update because they have limited processing power or long operating lifecycles. This makes planning especially important for infrastructure that must remain secure for many years.

What Should Businesses Do Now?

Organisations do not need to wait for a powerful quantum computer to emerge before preparing.

They can begin by identifying where public-key cryptography is used, assessing how long their sensitive information needs protection and tracking the readiness of software and hardware suppliers.

They should also establish a plan for adopting standardised post-quantum algorithms where appropriate. In some situations, hybrid systems that combine traditional and post-quantum methods can support a gradual transition.

The process needs careful testing because cryptographic changes can affect performance, interoperability and existing security controls.

The Future of Digital Security

Quantum computing has the potential to advance scientific research and solve specialised problems that are difficult for conventional machines. However, its long-term implications for encryption mean that the cybersecurity industry must prepare for technological change well in advance.

Post-quantum cryptography provides a practical route towards protecting digital information against future quantum threats. The transition will take time, but standards are already available to help organisations begin the work.

The biggest lesson is that cybersecurity cannot remain static. As computing technology advances, the methods used to protect information must evolve alongside it.