The issue gained fresh attention after Galaxy Digital pledged up to $5 million on July 21 to help strengthen Bitcoin’s resistance to future quantum attacks. While computers capable of breaking Bitcoin’s current cryptography do not exist today, some experts believe they could become a reality within the next decade.
The potential danger lies not in Bitcoin’s mining system or its blockchain history, but in the technology used to prove ownership of coins.
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Bitcoin relies on the SHA-256 hashing system for mining and maintaining its ledger. Even a powerful quantum computer would not be expected to efficiently break that system or rewrite Bitcoin’s historical transaction record.
The more significant vulnerability is Bitcoin’s elliptic curve digital signature algorithm, or ECDSA. The system is used to verify that someone controlling a wallet has the right to spend its coins.
A sufficiently powerful quantum computer could theoretically use a wallet’s publicly exposed information to calculate its private key. If that became possible, an attacker could potentially take control of vulnerable Bitcoin holdings.
That threat could be enormous. About one-third of existing Bitcoin is estimated to have public keys exposed on the blockchain, creating a potential target for future quantum attacks.
The timing, however, remains highly uncertain.
Some estimates suggest quantum computers capable of breaking Bitcoin’s cryptography could emerge in as little as five years. Others are considerably more optimistic. Blockstream CEO Adam Back has estimated that the technology could still be 20 to 40 years away.
Bitcoin developers are already considering ways to prepare for the possibility.
One proposal, BIP-360, would introduce a new type of Bitcoin address designed to protect coins against quantum attacks. But it would not automatically solve the problem for older wallets whose public keys are already exposed.
That includes the Bitcoin holdings believed to belong to the cryptocurrency’s pseudonymous creator, Satoshi Nakamoto. Estimates put those holdings at around 1.1 million BTC, a substantial portion of Bitcoin’s maximum supply of 21 million coins.
Another proposal, BIP-361, has proved far more controversial. It would potentially force the retirement of coins associated with older signatures after a five-year transition period. Supporters argue that such a move could protect the network from a future quantum attack, while critics say it could effectively override the property rights of people whose Bitcoin has remained untouched for years.
That highlights what may ultimately be Bitcoin’s biggest quantum problem.
The technology needed to create quantum-resistant cryptography already exists. The much harder challenge could be convincing Bitcoin’s decentralized developer and user community to agree on how — and when — to implement it.
For now, the quantum threat remains theoretical. There is no known quantum computer capable of breaking Bitcoin’s ECDSA protection, meaning the technology is not an immediate reason for investors to panic.
But Galaxy Digital’s $5 million commitment underscores why the issue is increasingly being treated as a long-term security problem rather than merely a science-fiction scenario.
