Google has cautioned that a sufficiently powerful quantum computer could intercept and steal funds from a live Bitcoin transaction in about nine minutes. The company said this could be done by deriving a private key from the briefly exposed public key before the payment is finalized. It estimated the chance of success for such an attack at just under 41% and urged a sector-wide shift to post-quantum cryptography by 2029.
The Google-led study described its hardware assumptions as conservative while withholding full algorithmic detail for security reasons and concluded that cryptocurrency transactions could be intercepted before recording on-chain, according to New Scientist.
While the company stressed that no such machine exists today, its researchers said new findings reduce the resources thought necessary to break protections used by Bitcoin and other digital assets. They said the new estimates shorten the time the industry has to settle on and execute a defensive roadmap.
"Momentous day for quantum computing"
The company’s paper said roughly 6.9 million Bitcoin may already be exposed, including around 1.7 million coins from the Satoshi era. By contrast, networks such as Ethereum that finalize transactions faster are deemed less susceptible to this real-time interception vector, the researchers said.
“Today is a momentous day for quantum computing and cryptography,” Justin Drake of the Ethereum Foundation wrote on X in response to the new estimates.
Google said it has worked since 2016 on a companywide transition to post-quantum protections and reiterated the need for the broader ecosystem to follow.