Quantum Computer vs Bitcoin: The Real Threat Behind the Buzz
📋 En bref (TL;DR)
- A researcher wins a 1 BTC bounty for breaking a 15-bit elliptic curve key on an IBM quantum computer
- Google Quantum AI publishes a whitepaper showing it would take fewer than 500,000 qubits to break Bitcoin — 20 times less than previously estimated
- Controversy: a Bitcoin developer replicates the bounty result using /dev/urandom (classical random noise)
- Bitcoin uses 256-bit keys — the gap from 15 bits represents a factor of 2241
- Several defense proposals exist: BIP-360, SPHINCS+, and the commit/reveal scheme
A researcher just won 1 bitcoin by cracking a cryptographic key on a quantum computer. Should you panic? No. But this result, combined with a whitepaper from Google published on March 31, 2026, has reignited the debate. The quantum threat is no longer science fiction. It is getting closer.
The “Q-Day Prize”: 1 BTC for Breaking an Elliptic Curve Key
Project Eleven, a post-quantum security startup founded by Alex Pruden, launched the “Q-Day Prize.” The challenge: break the largest possible ECC key on a real quantum computer. The reward: 1 BTC.
Researcher Giancarlo Lelli won the prize in April 2026. He successfully extracted a private key from a public key on a 15-bit elliptic curve. He used a 15-qubit circuit (10 logical + 5 ancillary) on IBM’s 133-qubit quantum computer.
The previous record belonged to Steve Tippeconnic. He had broken a 6-bit key in September 2025 on the same type of machine. Lelli thus improved performance by a factor of 512 in just seven months.
The Controversy: Quantum Noise or Real Breakthrough?
The result immediately sparked debate. Bitcoin developer Yuval Adam reproduced the experiment by replacing the quantum computer with /dev/urandom — a simple classical random number generator. The result was identical.
Adam explained: “I forked the winning repo, removed the IBM quantum calls, and replaced them with random bytes. Every recovered key is identical byte for byte.” According to his analysis, with 20,000 attempts against a modulus of 65,173, random chance alone gave a 26% probability of success.
Developers Jonas Schnelli and James O’Brien confirmed this analysis. The “community note” on X sums up the situation: the results are indistinguishable from random noise. In plain terms, the quantum machine demonstrated no real advantage over a simple coin flip.
Google Reduces the Resources Needed to Break Bitcoin by 20x
Meanwhile, a far more serious publication has cryptographers worried. On March 31, 2026, Google Quantum AI published a whitepaper in collaboration with the Ethereum Foundation and Stanford University.
Their conclusion: breaking Bitcoin’s secp256k1 cryptography would require fewer than 500,000 physical qubits. That is roughly 20 times fewer than previous estimates. More precisely, the computation would need either 1,200 logical qubits and 90 million Toffoli gates, or 1,450 logical qubits and 70 million gates.
Crucial caveat: no current machine has even 1% of that capacity. The largest existing quantum processor has roughly 1,000 qubits, far from the 500,000 required. Google has set 2029 as the deadline to migrate its own infrastructure to post-quantum cryptography.
1.7 Million BTC Exposed: Bitcoin’s Achilles’ Heel
The real problem does not affect all bitcoins. Modern addresses (P2PKH and later) only reveal their public key when spending. A quantum attacker would have just a few minutes to act.
However, 1.7 million BTC sit in legacy P2PK addresses. These addresses permanently expose their public key on the blockchain. Among them are Satoshi Nakamoto’s bitcoins — approximately 1.1 million BTC, worth over $85 billion at current prices.
If a sufficiently powerful quantum computer were to emerge, these funds would be the first at risk. That is why the Bitcoin community is already working on solutions.
Solutions in Development: BIP-360, SPHINCS+, and Commit/Reveal
Several proposals aim to protect Bitcoin against the quantum threat:
BIP-360 (Pay-to-Merkle-Root) introduces a new transaction type that removes the public key from the blockchain. Without a visible public key, a quantum computer has nothing to attack. However, this protection only applies to new funds.
SPHINCS+ (SLH-DSA), standardized by NIST in August 2024, is a quantum-resistant signature algorithm. Its drawback: signatures grow from 64 bytes to 8 kilobytes or more, significantly increasing block size.
Tadge Dryja, co-creator of the Lightning Network, proposes a commit/reveal scheme. The idea: split each transaction into two steps. First publish an encrypted hash, then reveal the transaction. This protects the mempool from quantum attacks.
Finally, Hunter Beast has proposed “Hourglass V2” for the 1.7 million BTC already exposed. The controversial idea: limit sales to one bitcoin per block to prevent a market crash. Some view this as an infringement on the fundamental right to spend your own coins.
Should You Worry Today?
No, not right now. The gap between 15 bits and Bitcoin’s 256 bits represents a factor of 2241. That is an engineering chasm no one will cross tomorrow. Google’s whitepaper is a resource estimate, not a timeline.
That said, the trend is clear. Progress is exponential. Project Eleven, backed by $26 million from Coinbase Ventures and Castle Island Ventures, is actively building post-quantum infrastructure. Justin Sun has announced a quantum transition for TRON by the end of 2026.
The message is simple: Bitcoin is not in immediate danger, but the community must act now to avoid being caught off guard. Bitcoin’s decentralized governance, which requires consensus for every change, makes this transition particularly slow. And that is precisely what worries experts.
Glossary
- ECC (Elliptic Curve Cryptography): a cryptographic method used by Bitcoin to secure transactions with public and private key pairs
- Qubit: the basic unit of quantum information, equivalent to a classical bit but capable of existing in multiple states simultaneously
- secp256k1: the specific elliptic curve used by Bitcoin to generate public/private key pairs
- Blockchain: a decentralized and immutable digital ledger that records all Bitcoin transactions
- Mempool: the waiting area where unconfirmed Bitcoin transactions queue until they are included in a block
Frequently Asked Questions
Can a quantum computer break Bitcoin today?
No. The largest current quantum processor has roughly 1,000 qubits. Breaking Bitcoin’s cryptography would require at least 500,000 physical qubits according to Google. We are very far from that. Learn more about Bitcoin’s security
What does the 15-bit record broken by a quantum computer mean?
A researcher extracted a private key from a 15-bit elliptic curve on an IBM machine. Bitcoin uses 256-bit keys. The gap represents a factor of 2^241 — an immense technological chasm.
Are Satoshi Nakamoto's bitcoins at risk?
The ~1.1 million BTC attributed to Satoshi sit in P2PK addresses that expose their public key. They would be among the first vulnerable if a sufficiently powerful quantum computer emerged. Discover who Satoshi Nakamoto is
How can Bitcoin protect itself against the quantum threat?
Several solutions are under development: BIP-360 hides the public key, SPHINCS+ offers quantum-resistant signatures, and the commit/reveal scheme protects pending transactions.
When will the quantum threat become real for Bitcoin?
No one can give a precise date. Google is targeting 2029 to migrate its own infrastructure. Experts estimate that a quantum computer capable of breaking Bitcoin could emerge within the next 10 to 15 years.
Sources
This article is based on the following sources:
- Google Research – Safeguarding cryptocurrency by disclosing quantum vulnerabilities
- The Block – Researcher breaks 15-bit elliptic curve key, wins 1 bitcoin bounty
- Bitcoin.com News – IBM Quantum cracks 15-bit ECC key, but devs say random bits match
- CoinDesk – Bitcoin’s $1.3 Trillion Security Race
- Cryptoast – Researcher wins 1 BTC for breaking an elliptic curve key
How to cite this article:
Fibo Crypto. (2026). Quantum Computer vs Bitcoin: The Real Threat Behind the Buzz. Retrieved from https://fibo-crypto.fr/en/blog/quantum-computer-bitcoin-real-threat-secp256k1
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