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A quantum computer has for the first time cracked a 15-bit cryptographic key
Independent researcher Giancarlo Lelli used a publicly accessible quantum computer to crack a 15-bit elliptic curve key — the mathematical foundation of digital signature schemes that secure the networks of Bitcoin, Ethereum, and most blockchains.
The post-quantum security startup Project Eleven called the event “the largest quantum attack on cryptography to date.” Project Eleven awarded Lelli the Q-Day Prize of 1 BTC. Representatives of the startup said that Lelli derived the private key from the public one within a search space of 32,767 possibilities, using a variant of Shor’s algorithm, which helps solve discrete logarithm problems on elliptic curves (ECDLP).
Last September, engineer Steve Tippeconnic cracked a six-bit elliptic curve key on a 133-qubit IBM quantum computer. According to Project Eleven, this was the first public demonstration of such a hack on quantum hardware. However, Lelli’s result surpasses Tippeconnic’s achievement by 512 times. Nevertheless, the achieved result is still far from breaking Bitcoin: the blockchain of the leading cryptocurrency uses 256-bit elliptic curve cryptography to protect wallets.
“The distance from 15 bits to 256 bits is large, but the gap is increasingly being viewed as an engineering problem rather than a fundamental physical one. Lelli’s demonstration highlights the need to transition to post-quantum cryptography as soon as possible,” Project Eleven stated.
According to the project, about 6.9 million bitcoins are stored in wallets whose public keys are visible on the blockchain and therefore vulnerable to future truly powerful quantum attacks.
Project Eleven is developing solutions intended to help protect digital assets and infrastructure from threats related to the development of quantum computing. Its investors include Castle Island Ventures, Coinbase Ventures, and Variant.
Previously, Google Research estimated that breaking 256-bit elliptic curve cryptography could require fewer than 500,000 physical qubits (the basic units of information in quantum computing). Later, in a joint study by the California Institute of Technology and the quantum startup Oratomic, an even lower estimate was given — just 10,000 qubits. At the same time, modern quantum systems are still far from even the second threshold.
