Bitcoin’s record high value of more than $106,000 is under threat by ever-evolving quantum computing that could undo its foundational encryption, some computational science experts say. If the cryptocurrency wants to avoid an attack that would overhaul its means of protecting transactions, it would need to undergo a costly—and time-consuming—update process that could take nearly a year, according to new research.
A study from the University of Kent’s School of Computing calculated that if Bitcoin were to try to effectively protect itself from the threat quantum computing poses, it would take a protocol update that would take the cryptocurrency offline for 76 days. More realistically, the study calculated, Bitcoin would instead designate 25% of its server to a protocol update and allow its users to continue to mine and trade at a slower rate. But in that scenario, the downtime would take about 305 days. That’s 10 full months.
Carlos Perez-Delgado, one of the study’s authors and senior lecturer at the University of Kent, couldn’t put a price tag on the cost of the downtime, but it could be eye-watering. Just one hour of downtime can cost a business $500,000, according to the Ponemon Institute . If Bitcoin had 76 days of downtime—what the study deemed the most optimum scenario—the update could cost $912 million.
“Bringing your technology down…can be very, very costly, even if it's on for a few minutes or a few hours,”, Perez-Delgado told Fortune. “What we're showing here in our paper is that for Bitcoin, or any system like Bitcoin, you take days, weeks or even months, to perform the update.”
But this slow and expensive action is necessary, given the emerging and “imminent” quantum technologies that threaten to easily unravel encryption codes that protect swaths of online data, according to Perez-Delgado. Google’s Willow chip announced last week promises to eventually complete computations in five minutes that would take the most powerful supercomputer today 10 septillion years. The power of the technology has stoked optimism in some experts, and fear in others.
“If I had a large quantum computer right now, I could essentially take over all the Bitcoin,” he said. “By tomorrow, I could be reading everybody's email and getting into everybody's computer accounts, and that's just the fact.”
Perez-Delgado doesn’t mean to sound alarmist. IBM predicts we likely won’t have quantum computers big enough to threaten the current form of encryption anytime this decade , and its threat to cryptography remains hypothetical until then. But all tech entities are going to have to be proactive should it become a threat, Perez-Delgado warned.
“The indisputable fact that nobody can argue is that when we do get there, our current securities, the cybersecurity systems—which includes everything from Bitcoin to email—will be in great danger,” he said.
Quantum computing’s threat to Bitcoin
At the core of quantum computing’s threat to cryptocurrencies is its ability to perform exponentially more operations than classical computing. While classical computers use binary bits to perform actions one at a time, quantum computers use qubits, which can represent both the 0s and 1s that make up binary operations, allowing quantum computing to simultaneously perform functions classical computing would be able to fulfill only one at a time.
Today’s ubiquitous means of protecting information and transactions through public-private key encryption—essentially using a pair of different “keys” to lock and unlock data—are no match for powerful quantum computing, Perez-Delgado said. Instead, any technology using encrypted information will have to turn to “ post-quantum ,” or “quantum-safe,” cryptography.
For centralized companies like Google, this replacement could be as simple as asking users to download new software or to take down its server for an hour or a day to patch it with new cryptography programs. But for decentralized cryptocurrencies, implementing new encryptions is no cakewalk. With 275 million Bitcoin investors on a platform with no centralized authority, no one entity can introduce an update. It’s a quagmire for Bitcoin, which has attracted users expressly because it's decentralized.
Moreover, the process of updating Bitcoin’s blockchain would involve updating each individual transaction. Combined with Bitcoin’s notoriety of being slow to process transactions , and you have an encryption undertaking that could move at a snail’s pace.
Perez-Delgado doesn’t see his research as “certain doom” for Bitcoin. The cryptocurrency has other options to handle a major update, including de-throttling, or speeding up, its block time, or time necessary to move or update transactions to the blockchain. But like the solution of implementing downtime to update the blockchain, speeding up the block time could come at the expense of the platform’s ability to handle user traffic.
“Those side effects are well worth the cost,” Perez-Delgado said.
