Researcher Cracks 15-Bit Key on Quantum Hardware, 512 Times Larger Than Prior Record

Independent researcher Giancarlo Lelli broke a 15-bit elliptic curve key on publicly accessible quantum hardware, 512 times larger than the previous public demonstration in September 2025. Lelli won Project Eleven’s one bitcoin Q-Day Prize for the feat.

CoinDesk reported that while this is far from threatening bitcoin’s 256-bit elliptic curve security, it highlights advancing quantum capabilities relevant to cryptocurrencies.

Google's paper this month showed a quantum attack could be run with far fewer resources than previously estimated, in a window that races against bitcoin's own block times. The paper indicated that such attacks could break the cryptography protecting bitcoin wallet ownership.

Quantum computers cannot disrupt bitcoin mining or the blockchain ledger itself, but they could eventually break the cryptography that protects bitcoin wallet ownership.

9 million bitcoin, about one-third of everything ever mined, sits in wallets whose public keys are already permanently visible onchain. This includes Satoshi Nakamoto’s early holdings and any coins spent from since 2021’s Taproot upgrade, which are exposed to future quantum attacks because their public keys are visible on-chain.

Satoshi Nakamoto holds roughly 1 million bitcoin, untouched since the network's early days, in the exposed category.

9 million exposed bitcoin is from the network's first years, stored in an address format that published the public key by default. Any bitcoin wallet that has ever been spent from reveals the key for whatever remains. The 2021 Taproot upgrade activated and expanded the exposure problem by publishing the key protecting remaining bitcoin when spent since activation.

Bitcoin mining uses hashing that quantum computers cannot meaningfully break. The bitcoin ledger and the rule that new bitcoin can only be created through mining would survive a quantum attacker. Blocks would still get produced and the bitcoin chain would keep running despite a quantum attacker.

Bitcoin wallets are protected by math that turns a secret private key into a public address. Turning a secret private key into a public address takes milliseconds. Going from public address back to the private key would take a regular computer longer than the age of the universe.

A quantum algorithm called Shor's collapses the gap between deriving public address from private key and the reverse. Nic Carter wrote on X that 'Elliptic curve cryptography is on the brink of obsolescence,' referring to the math that secures bitcoin wallets.

Carter described Ethereum's approach as 'best in class' and bitcoin's as 'worst in class,' citing developers who 'deny, gaslight, gatekeep, bury heads in sand' rather than engage with the problem.

Ethereum has had a formal quantum-resistant program since 2018. The Ethereum Foundation runs four teams working on the post-quantum migration full-time, with more than ten independent developer groups shipping weekly test networks. Ethereum's plan maps specific upgrades across four upcoming network-wide changes to new math that quantum computers cannot break.

Org, to publish its progress. BIP-360 is a formal proposal from a group of developers and researchers to add new quantum-safe address types that holders could voluntarily migrate to. BitMEX Research proposed a system that would install detection to trigger defensive action if a quantum attack is observed on the network.

Adam Back said at a conference earlier this month that 'Quantum computing still has a lot to prove. ' Back said bitcoin should prepare now with optional upgrades built in advance so the network can migrate when needed.