The notion that quantum computing poses an imminent threat to bitcoin's security has been a topic of discussion in recent times. However, according to recent research papers, the idea of a quantum computer attacking the bitcoin blockchain is more complex than initially thought.
Two key types of math underpin bitcoin's security, and quantum computers pose a threat to them in different ways. One method, known as Shor's algorithm, targets wallet security by allowing a powerful quantum computer to derive a private key from a public key.
On the other hand, Grover's algorithm applies to mining and offers a theoretical speedup on the trial-and-error search miners perform. Nevertheless, the advantage of Grover's algorithm largely disappears when attempting to build the machine. Two recent papers highlighted the challenges of a quantum computer attack on the bitcoin blockchain. The first paper, published in March 2026, examined whether a quantum computer could out-mine BTC using Grover's algorithm.
The researchers found that running Grover against SHA-256, the math formula bitcoin miners use to add new blocks to the blockchain, would be physically impossible. The energy required to power such a machine would be equivalent to a small star. Another paper, which used a 1981 VIC-20 home computer and a dog, replicated every major quantum factoring breakthrough of the past two decades. The authors demonstrated that the quantum factoring records are mostly exaggerated and that the underlying point is serious.
Factoring is the math problem at the heart of most modern encryption, and Shor's algorithm is the reason people worry that quantum machines could eventually break it. However, the authors found that nearly every demonstration so far has cheated by picking numbers whose hidden prime factors were only a few digits apart or by running the hard part of the problem on a regular computer first. The takeaway is not that quantum computing is harmless, but rather that the threat is more nuanced. The real vulnerability is bitcoin wallets, not mining, and millions of bitcoin sit in older or reused addresses where key information is already exposed on the blockchain.
Recent research suggests that the computing power needed for a quantum attack could fall sharply, but building such a machine is currently physically impossible and requires engineering advances that haven't been done yet. Developers are already working on fixes, including ways to reduce key exposure and new types of signatures designed to withstand quantum attacks.