Experts warn quantum computers could forge Bitcoin digital signatures, enabling unauthorized transactions.
Macro & Markets ·
Quantum computers could eventually forge Bitcoin's digital signatures, enabling attackers to authorize transactions from addresses whose public keys have been exposed, according to experts cited in recent analysis. Current quantum systems remain too small and unstable to pose an immediate threat to the network's cryptography, but advances from major tech companies have narrowed the timeline to what researchers call "Q-Day"—the moment when a sufficiently powerful machine could compromise older Bitcoin addresses holding more than $452 billion in vulnerable funds.
A successful attack would exploit a "harvest now, decrypt later" strategy, in which attackers copy public keys from the blockchain and later process them through quantum computers using Shor's algorithm to derive private keys. Once recovered, an attacker could move coins from compromised addresses, and the forged signatures would appear legitimate to the Bitcoin network, allowing miners to include such transactions in blocks without detecting the fraud.
Upgrading Bitcoin to resist post-quantum attacks will require years of development, yet the exact timeline of when quantum computers may achieve sufficient capability remains unknown. Developers are exploring post-quantum signature schemes and potential migration paths, but the cryptocurrency community has struggled to reach consensus on implementation, leaving uncertainty about whether the network will be ready before the threat materializes.