Quantum Threat to Bitcoin May Be Closer Than Expected, Google Says

Highlights:

• Google warned that quantum computers may break Bitcoin-era encryption sooner than many in crypto expected.
• The company urged blockchain developers to begin shifting toward post-quantum security standards now.
• Google said Bitcoin is not at immediate risk, but future transaction attacks remain possible.

Google researchers have issued a timely warning that quantum computers could break the cryptographic security protecting Bitcoin and other cryptocurrencies sooner than many experts anticipated. In a new research paper published on 31 March, the tech giant revealed that future quantum machines may need far fewer resources to crack the elliptic curve cryptography currently securing most blockchain networks.

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The company urged blockchain communities to start moving toward post-quantum cryptography before the risk becomes real. In its new whitepaper, Google said a future quantum computer might be able to break that protection. The paper explained two possible ways this could happen. One method would need fewer than 1,200 logical qubits and 90 million Toffoli gates. The other would need fewer than 1,450 logical qubits and 70 million Toffoli gates.

Google also said that, under normal hardware assumptions, this kind of attack could happen in minutes on a superconducting quantum computer with fewer than 500,000 physical qubits. That is a big change because it is around 20 times lower than earlier estimates.

🚨BREAKING: GOOGLE WARNS 6.9M BITCOIN WILL BE VULNERABLE WHEN QUANTUM COMPUTERS BECOME POWERFUL ENOUGH

A new Google Quantum AI whitepaper has identified approximately 6.9 million Bitcoin $BTC vulnerable to future quantum at-rest attacks.

Around 1.7 million BTC sits in old… pic.twitter.com/pCwKrhXL4e

— BSCN (@BSCNews) March 31, 2026

Google Says the Crypto Industry Should Prepare Now

Google said the crypto industry should not wait until quantum computers become a real threat. Instead, the company urged blockchain communities to start moving to post-quantum cryptography, or PQC. This is a new type of security designed to protect systems from quantum computer attacks.

In its blog post, Google said workable solutions already exist. However, it also warned that the shift will take time. Because of that, the company said early action is important. Google also advised users and developers to avoid reusing wallet addresses that could be exposed more easily. In addition, it said the industry should start a wider discussion about what to do with abandoned coins in a post-quantum future.

The company did not say BTC is about to collapse. Instead, Google said the risk is more complex, and some parts of blockchain systems are stronger than many people think. In the whitepaper, the company explained that Bitcoin’s proof-of-work system is not directly exposed to this same kind of quantum attack. Google also noted that many public keys stay hidden until someone spends their coins. That means not every wallet is openly exposed all the time.

The paper says that about 6.9 million Bitcoins may already be vulnerable to future quantum attacks because their public keys have been exposed. That includes over 1.7 million Bitcoin in early wallets that show the public key by default, along with more coins exposed through repeated address use.

Still, the company warned about a possible future risk known as an “on-spend” attack. In simple terms, this could happen if a powerful quantum computer spots a public transaction, breaks the key fast enough, and sends a fake transaction before the real one is confirmed. 

Google Outlines Safe Disclosure and 2029 Post-Quantum Shift

Google said it shared the research carefully to avoid giving hackers a clear roadmap. Instead of publishing the full technical details of the attack, the researchers used something called a zero-knowledge proof. This method allows other experts to verify that the research is valid without revealing sensitive technical information that could be misused.

Google also said it worked with the U.S. government on how to release this research safely. The company added that other research teams should follow a similar approach when sharing sensitive discoveries, so the public can be informed without increasing security risks.

The warning also matches Google’s wider security plan. In a separate blog post published on 25 March, Google said it aims to switch its own systems to post-quantum cryptography by 2029. The company said this timeline reflects recent progress in quantum hardware, better error correction, and new estimates showing that quantum attacks may need fewer resources than once thought.

🚨JUST IN: GOOGLE SETS 2029 DEADLINE AS QUANTUM THREAT LOOMS OVER BITCOIN

Google has set a 2029 deadline for post-quantum cryptography migration, warning quantum risks are approaching faster than expected.

The company says current encryption standards could eventually be… pic.twitter.com/LbGSmms3RQ

— BSCN (@BSCNews) March 26, 2026

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