At the end of March 2026, a white paper released by Google's quantum artificial intelligence team revealed that a sufficiently powerful quantum computer could theoretically crack Bitcoin's underlying encryption with only one-twentieth of the resources previously estimated, and the cracking time could even be shortened to about 9 minutes.This discovery significantly lowers the threat threshold of "quantum doomsday". Currently, approximately 6.9 million Bitcoins (approximately one-third of the total supply) are at direct risk because their public keys have been permanently exposed on the blockchain.
It is worth noting that Google has significantly advanced the deadline for "quantum doomsday" emergency preparation to 2029. The so-called "quantum doomsday" refers to the moment when quantum computers can break public key cryptography algorithms.
By then, almost all daily passwords such as bank cards and social media accounts will be at risk, and the foundation of passwords we rely on will be shaken.
The Google report provides a specific attack scenario: when a Bitcoin transaction is broadcast to the network and waits for confirmation in the "memory pool", an attacker can use a quantum computer to launch an attack.
Bitcoin’s average transaction confirmation time is approximately 10 minutes. Google research has found that under certain conditions, the attack process for a quantum computer to derive a private key from a public key only takes about 9 minutes. In this race against transaction confirmation time, an attacker will have about a 41% chance of stealing the private key and "cutting off" the funds before the transaction is officially recorded.
Most cryptocurrencies, including Bitcoin and Ethereum, use elliptic curve cryptography as the underlying algorithm. Under traditional computing, exhausting all possible keys would take far longer than the lifetime of the universe.But instead of trying each one one by one, a quantum computer explores all possibilities simultaneously and filters out the correct answer through interference.
The Google report also revealed another more immediate and pressing threat: approximately 6.9 million Bitcoins are currently stored in wallets whose public keys have been permanently exposed, including 1.1 million belonging to Bitcoin founder Satoshi Nakamoto. For this part of the assets, once a sufficiently powerful quantum computer comes out, attackers can easily crack and steal funds at any time without a 9-minute "race".
A few weeks before the release of the Google report (March 12, 2026), Ark Investment released a report stating that today’s quantum computers are far from reaching the threshold of posing a threat in terms of computing power, and any meaningful breakthrough is likely to first affect the broader Internet security field, not just Bitcoin.