Quantum computing has reached an inflection point. Venture capitalists are pouring funding into the technology, and public initiatives are picking up pace as they explore the role it could play in our society.

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Itself a relatively new innovation, blockchain technology allows for parties to perform peer-to-peer transactions in a system not governed by a central authority. Instead of trusting a central authority, blockchain provides a trust framework that is enabled by the properties of cryptographic algorithms.

As long as these algorithms are considered secure, activities that do not abide by the rules, such as illegitimate cryptocurrency transactions, are discarded, incentivizing actors to behave honestly. They are assumed to be secure against powerful supercomputers, now and for the foreseeable future.

But, as quantum computers evolve, this assumption is in danger of being upended — potentially exposing hundreds of billions of dollars’ worth of cryptocurrencies to sophisticated cyber criminals.

Despite quantum computing being in a relatively early stage of development, specialists are already forecasting the potential of quantum-equipped actors to steal vast quantities of cryptocurrencies by abusing the advantage that quantum computing can provide.

New technology and new algorithms could, in the near to medium term, subvert established digital security practices using two key types of attack: the storage attack and the transit attack.

Storage attack

In the so-called storage attacks, an adversary would target vulnerable addresses — those in which the wallet’s public key is held on the blockchain — to steal funds.

Hundreds of billions of dollars’ worth of cryptocurrencies could be vulnerable to storage attacks.

The computing power needed to carry out these assaults is estimated at around 10 million qubits — a unit of measurement best understood as the equivalent to a regular bit used in standard computing.

That is significantly more than the hundred or so qubits we currently have available. However, scientists have predicted that quantum computers could reach the 10 million mark within 10 or 15 years.

Protecting from these attacks requires fund owners to avoid vulnerable addresses or move their funds out of them into addresses where the public key is not published — perhaps easier said than done.