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 going through numerous safety threats. Recently, lots has been stated in regards to the potential menace from quantum computer systems. Nevertheless, 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 offers 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 dear.
- Prior to now, Bitcoin Gold and Ethereum Traditional went by profitable 51% assaults, ensuing within the theft of cash by double-spending. All through historical past, the Bitcoin blockchain has been secure from the 51% assaults.
- In keeping with 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 doable 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 going through its particular threats: quantum computer systems and, what’s extra necessary, a doable 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 items.
What’s a 51% assault?
As Bitcoin mining is dear and requires particular {hardware}, miners don’t have a possibility to mess with the ledger knowledge. Every node “votes” through 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 right knowledge as they rely upon the Bitcoin blockchain’s integrity, which supplies it worth.
Nevertheless, as soon as half of the entire hashrate within the system is managed by a single entity (an individual or a bunch of plotters), it has the ability to vary the information within the Bitcoin ledger. It would 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 realize management over the Bitcoin blockchain.
Within the early days of Bitcoin, mining was accessible to any PC proprietor. Nevertheless, as mining is predicated on competitors the place the luckiest miner has to have a better hashrate stage than most rivals, computer systems and even GPUs and FPGAs shortly turned out of date for mining. In 2013, the primary ASICs (units specialised for Bitcoin mining) hit the market. Quickly, Bitcoin mining became a multi-million-dollar business, requiring a lot funding and services stuffed with buzzing ASIC units. In October 2025, Bitcoin mining problem reached a brand new most.
It makes hacking Bitcoin through a 51% assault a tough and costly job. Because the mining problem goes up, every year the prices of a 51% assault are getting greater.
Campbell Harvey’s findings
Whereas a 51% assault is dear, its worth will not be unthinkable. Such networks as Bitcoin Gold and Ethereum Traditional suffered a number of 51% assaults after 2017. Every certainly one of them resulted in a single million plus value of crypto stolen in every separate case. In August 2025, Qubic mining pool claimed it acquired 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 price “solely” $6 billion:
“{Hardware} is the biggest 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 information heart about $0.13 billion per week. All instructed, a one-week assault would price about $6 billion, or 0.26% of the bitcoin community’s complete worth.”
The analysis is predicated on the next metrics:
- Bitcoin’s annual output is 164,363 BTC
- Power utilization is 166.4TWh
- Whole price is $12 trillion
- Whole power price is $8.4 trillion
- Whole price 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 each day quantity at $60 billion and standard BTC futures each day quantity at $10 billion. Harvey believes that opening a brief place on these markets earlier than a 51% assault might end in excessive income for attackers on high of returning $6 billion. Harvey provides that the motive might not be profit-related.
Nevertheless, 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 arduous, because the trade will in all probability 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 angle is that financial feasibility kills the 51% thesis. I reside in the actual world, and I’m not involved.”