Quantum computers are knocking on the blockchain: record-breaking ECC key hack

Independent researcher Giancarlo Lelli conducted a demonstrative experiment using a real quantum computer and was able to select a private 15-bit key in the elliptic cryptography system. The experiment was conducted on publicly available quantum equipment through a cloud service and is currently the largest practically implemented quantum hacking of a cryptographic key based on ECC. For his work, Lelli received a reward of 1 BTC from the AMeleven project, which deals with post-quantum security.

A variant of Shor's algorithm, adapted for the task of discrete logarithm on elliptic curves, was used for the attack. The researcher only knew the public key, and the task was to restore the corresponding private key. A key of only 15 bits in length was chosen as the target - this means a search space of 32,767 possible values. Despite the tiny size by the standards of real cryptography, it is precisely the successful recovery of a private key from an open one that makes the experiment a full-fledged quantum attack on ECC, not a theoretical demonstration on paper.

Before this, the record belonged to engineer Steve Tippeconnic, who in 2025 demonstrated the hacking of a 6-bit ECC key on a 133-qubit IBM Torino processor. The transition from 6 to 15 bits looks modest, but in terms of combinatorics, this is an increase in the space of possible keys by 512 times. Against this background, the current result is logically positioned as a new public frontier for really working quantum attacks, conducted not in laboratories with closed access, but on commercially available "hardware".

At the same time, the news does not pose an immediate threat to cryptocurrencies and traditional financial systems. In Bitcoin, Ethereum and other popular blockchains, 256-bit keys are used on basic elliptic curves, which is colossally more than the values of the conducted experiment.

Nevertheless, the significance of the experiment goes beyond pure mathematics. In fact, the community has received a clear confirmation: a quantum attack on elliptic cryptography is not only theories and estimates, but a working prototype, albeit on a "toy" bitness. Against this background, pressure on the industry is increasing in terms of transitioning to post-quantum signature and encryption schemes, especially for systems where data confidentiality must be maintained for decades. Banks, government structures and large corporations are increasingly including the quantum factor in their information protection roadmaps.

There is traditionally a lot of hype around the topic of quantum hacking, and such news is easily presented in the spirit of "the end of cryptography" or "a quantum computer is already breaking bitcoin". In practice, the current record is a technological milestone and a demonstration of principle, not a catastrophic leap towards hacking real crypto wallets. The key conclusion for the market is that the transition to post-quantum cryptography needs to be prepared in advance, while threats remain theoretical for combat systems, and not wait for the moment when quantum hardware catches up with the scale of real keys.