First Quantum Hack in Crypto Is Here, but Bitcoin Pioneer Adam Back Labels It as Fake
TL;DR
Researcher Giancarlo Lelli cracked a 15-bit ECC key using a quantum computer, earning 1 BTC from Project Eleven. Bitcoin pioneer Adam Back dismissed the claim as misleading, arguing it doesn't pose a real threat to classical encryption.
Key points
- Giancarlo Lelli cracked a 15-bit ECC key on a quantum computer
- He received 1 BTC from Project Eleven for this achievement
- Adam Back dismissed the claim as misleading and not a real threat
- The complexity of cracked keys has increased significantly
- Breaking Bitcoin encryption is viewed as a matter of engineering refinement
Mentioned in this story
The crypto industry is discussing a high-profile precedent as researcher Giancarlo Lelli received a reward of 1 BTC from Project Eleven for successfully cracking a 15-bit ECC key on a quantum computer. While some see this as the beginning of the end for classical encryption, Adam Back has led the camp of skeptics, stating that behind the loud headline lies ordinary statistics.
Lelli used a cloud-based quantum computer and a modified Shor's algorithm to derive the key. Project Eleven highlights the progress over the past seven months - the complexity of cracked keys has increased from 6 to 15 bits, a 512-fold jump.
By their logic, breaking Bitcoin becomes merely a matter of engineering refinement.
Why Bitcoin pioneer Adam Back isn't worried about the 15-bit key breach
The head of Blockstream, Adam Back, dismissed the claim entirely. According to him, the researcher did not solve the problem using a quantum method such as discrete logarithm computation, but simply checked outputs classically that are indistinguishable from noise.
Back agrees with the explanation that Lelli's method is equivalent to simple guessing. At such a small key size of 15 bits, the probability of success through brute force is so high that the involvement of a quantum computer becomes an expensive decoration.
read the community note: it means it doesn't do what they have been claiming it does. it does not compute the discrete log of anything using quantum.
— Adam Back (@adam3us) April 26, 2026
Adam Back remains confident regarding quantum resistance. His view as of April 2026 is that quantum machines will first break state secrets and banking systems, not Bitcoin.
The criticism was supported by former Bitcoin Core developer Jonas Schnelli, who provided specific numbers: out of a total keyspace of 32,497 possibilities, the researcher tested around 20,000. "This is a 50% probability, like flipping a coin. Quantum computing contributed nothing useful here", Schnelli concluded.
As of now, the "first-ever quantum hack" is regarded by experts as more of a marketing move than a technical breakthrough. Back maintains that as long as Bitcoin keys remain 256 bits long, such experiments remain nothing more than a sandbox exercise.
Q&A
What did Giancarlo Lelli achieve with the quantum computer?
Giancarlo Lelli successfully cracked a 15-bit ECC key using a cloud-based quantum computer.
Why does Adam Back consider the quantum hack claim to be fake?
Adam Back argues that Lelli's method did not utilize true quantum techniques but rather classical checks that resemble noise.
What is the significance of cracking a 15-bit ECC key in crypto?
Cracking a 15-bit ECC key suggests potential vulnerabilities in encryption, but the increase in complexity from 6 to 15 bits is seen as a minor step in quantum computing advancements.
