Researcher uses quantum computer to crack key that protects Bitcoin
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The theoretical threat that quantum computers pose to the Bitcoin network moved a step closer to reality on Friday. Project Eleven, a startup focused on quantum security, awarded its "Q-Day Prize" to an independent researcher named Giancarlo Lelli.
The award follows the largest public demonstration of a quantum attack on the "elliptic curve" cryptography that currently secures over $2.5 trillion in digital assets, including Bitcoin and Ethereum.
Lelli successfully broke a 15-bit encryption key using publicly available quantum hardware. In simple terms, he used a variant of Shor’s algorithm to find a secret "private key" using only its public counterpart.
While this is supposed to be impossible for traditional computers, Lelli found the answer across a search space of 32,767 possibilities.
Related: After Google, largest U.S. crypto exchange warns of quantum threat
A rapid increase in difficulty
While Bitcoin operates at a much higher 256-bit scale, the speed of progress is accelerating. Lelli’s achievement represents a 512-fold jump in difficulty compared to the previous record set just seven months ago in September 2025, when Steve Tippeconnic cracked a 6-bit key.
Most notably, the winning entry did not come from a national laboratory or a private supercomputer. Instead, it was completed by an independent researcher using cloud-accessible hardware that anyone can rent.
Project Eleven CEO Alex Pruden highlighted that the winning entry did not come from a government laboratory, but from an independent researcher using cloud-based hardware.
"The resource requirements for this type of attack keep dropping, and the barrier to running it in practice is dropping with them," Pruden noted.
He added that with Google recently committing to being quantum-secure by 2029, the window for the rest of the industry to upgrade its security is closing.
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Millions of Bitcoin in the crosshairs
The risk is most acute for older "static" wallets that have already revealed their public keys on the blockchain.
Project Eleven estimates that roughly 6.9 million Bitcoin—nearly one-third of the entire supply—sit in these vulnerable addresses. This includes the legendary 1 million Bitcoin held by the creator of the network, Satoshi Nakamoto, which have remained untouched since the early years of the project.
As the capabilities of quantum hardware grow, developers across the industry are racing to build "post-quantum" defenses. A new proposal for the Bitcoin network, known as BIP-360, aims to introduce safer address types that can resist these emerging machines.
Other major blockchain platforms, including Ethereum, Ripple, and Tron, have also begun publishing their own transition plans to ensure their networks remain secure in the coming years.
