The crypto industry has been stirred by claims of a 'first-ever quantum hack' against Bitcoin, but prominent figures, including Bitcoin pioneer Adam Back, have forcefully refuted the narrative. On April 26, 2026, researcher Giancarlo Lelli announced he had successfully cracked a 15-bit elliptic curve cryptography (ECC) key using a cloud-based quantum computer and a modified version of Shor's algorithm. This achievement was supported by Project Eleven, which highlighted that the complexity of cracked keys had increased 512-fold from 6-bit to 15-bit over the past seven months, suggesting that breaking Bitcoin's encryption was merely a matter of engineering refinement.
However, Adam Back, CEO of Blockstream, quickly dismissed the claim. He argued that Lelli did not compute a discrete logarithm using quantum methods, but instead checked outputs classically that are indistinguishable from noise. Back stated, "It does not compute the discrete log of anything using quantum." He equated the method to simple guessing, emphasizing that at a 15-bit key size, brute force probability is so high that the use of a quantum computer is an expensive decoration. Former Bitcoin Core developer Jonas Schnelli supported this criticism with specific numbers: out of a total keyspace of 32,497 possibilities, Lelli tested around 20,000. Schnelli concluded, "This is a 50% probability, like flipping a coin. Quantum computing contributed nothing useful here."
Back remains confident in Bitcoin's quantum resistance, stating that quantum machines will first break state secrets and banking systems before threatening Bitcoin. He maintains that as long as Bitcoin keys remain 256 bits long, such experiments are merely a 'sandbox exercise' and a marketing move rather than a genuine technical breakthrough.
