Bitcoin is trusted by governments and monetary establishments. Respected buyers name it “digital gold,” and a few even declare it’s higher than gold. However all these, Bitcoin remains to be dealing with varied safety threats. Currently, quite a bit has been stated concerning the potential risk from quantum computer systems. Nonetheless, Duke College Professor Campbell Harvey revealed one other concern, particularly the relative cheapness of a 51% assault on the Bitcoin community.
Abstract
- If profitable, a 51% assault provides attackers management over the Bitcoin blockchain (or one other proof-of-work-based blockchain). To realize success, attackers should management over 50% of the mining hashrate, which is expensive.
- Prior to now, Bitcoin Gold and Ethereum Basic went via profitable 51% assaults, ensuing within the theft of cash via double-spending. All through historical past, the Bitcoin blockchain has been secure from the 51% assaults.
- Based on Harvey, to dominate within the hashrate manufacturing for one week, attackers would wish to spend “solely” $6 billion, which is lower than 0.5% of Bitcoin’s market capitalization. Harvey supplied a potential sensible use of such an assault.
Duke College Fuqua Faculty of Enterprise Professor Campbell Harvey launched a paper devoted to potential threats to Bitcoin. In an summary, Harvey likens Bitcoin to gold however outlines that Bitcoin is dealing with its particular threats: quantum computer systems and, what’s extra necessary, a potential 51% assault. He additionally acknowledges that Bitcoin has its benefits over gold. As an illustration, he mentions that “trendy alchemy” permits the manufacturing of extra gold, whereas Bitcoin’s provide can’t exceed 21,000,000 models.
What’s a 51% assault?
As Bitcoin mining is expensive and requires particular {hardware}, miners don’t have a chance to mess with the ledger knowledge. Every node “votes” by way of computing energy (hashrate) to validate transactions in new blocks, and nearly all of miners are voting for proper knowledge. Miners are motivated to vote for the proper knowledge as they rely on the Bitcoin blockchain’s integrity, which provides it worth.
Nonetheless, as soon as half of the full hashrate within the system is managed by a single entity (an individual or a gaggle of plotters), it has the ability to alter the information within the Bitcoin ledger. It should enable unhealthy actors to maneuver different folks’s bitcoins, successfully stealing them.
Whereas some criticize Bitcoin for its low decentralization stage, nobody in 16 years of Bitcoin’s existence has ever managed to achieve management over the Bitcoin blockchain.
Within the early days of Bitcoin, mining was accessible to any PC proprietor. Nonetheless, as mining relies on competitors the place the luckiest miner has to have the next hashrate stage than most rivals, computer systems and even GPUs and FPGAs rapidly grew to become out of date for mining. In 2013, the primary ASICs (gadgets specialised for Bitcoin mining) hit the market. Quickly, Bitcoin mining become a multi-million-dollar trade, requiring a lot funding and amenities full of buzzing ASIC gadgets. In October 2025, Bitcoin mining issue reached a brand new most.
It makes hacking Bitcoin by way of a 51% assault a tough and costly process. Because the mining issue goes up, annually the prices of a 51% assault are getting increased.
Campbell Harvey’s findings
Whereas a 51% assault is expensive, its worth is just not unthinkable. Such networks as Bitcoin Gold and Ethereum Basic suffered a number of 51% assaults after 2017. Every one in every of them resulted in a single million plus price of crypto stolen in every separate case. In August 2025, Qubic mining pool claimed it obtained over 50% of the hashing energy within the Monero community.
Professor Harvey calculated the prices and concluded that one week of domination on the Bitcoin blockchain would value “solely” $6 billion:
“{Hardware} is the most important expenditure, about $4.6 billion at present costs. The information heart construct would require $1.34 billion and the electrical energy to run the {hardware} and keep the info heart about $0.13 billion per week. All instructed, a one-week assault would value about $6 billion, or 0.26% of the bitcoin community’s complete worth.”
The analysis relies on the next metrics:
- Bitcoin’s annual output is 164,363 BTC
- Power utilization is 166.4TWh
- Complete value is $12 trillion
- Complete vitality value is $8.4 trillion
- Complete value per unit is $73,000 per 1 BTC unit
Harvey famous {that a} profitable 51% assault on Bitcoin would trigger a extreme worth drop, and hackers might nonetheless revenue from it and earn way more than $6 billion again. Harvey estimated BTC perpetual futures every day quantity at $60 billion and traditional BTC futures every day quantity at $10 billion. Harvey believes that opening a brief place on these markets earlier than a 51% assault might end in excessive earnings for attackers on prime of returning $6 billion. Harvey provides that the motive will not be profit-related.
Nonetheless, critics of Harvey’s warning argued that setting such an enormous mining operation would have taken years, and it wouldn’t go unnoticed. Greater than that, shorting a lot BTC within the circumstances of an ongoing 51% assault could also be onerous, because the change will most likely flag an operation as market manipulation and gained’t let it.
Commenting on Harvey’s analysis, Matt Prusak, president of American Bitcoin Corp., instructed Bloomberg: “My perspective is that financial feasibility kills the 51% thesis. I reside in the true world, and I’m not involved.”
