Time's Running Out for Bitcoin to Thwart Quantum Computing Threat, 6.9 Million BTC at Risk

Not all aspects of bitcoin are vulnerable to quantum computers. The bitcoin mining process, which involves adding new blocks to the blockchain, relies on a type of mathematics known as hashing that quantum computers are unable to crack. As a result, the blockchain itself and the rule that new bitcoins can only be created through mining would remain intact in the event of a quantum attack. New blocks would continue to be produced, and the chain would remain operational. However, ownership would be severely impacted. Bitcoin wallets are secured by a different type of mathematics that converts a private key into a public address that can be seen by anyone. This mathematics works effortlessly in one direction but not at all in the other, and it is the only thing that prevents a stranger from spending your coins. The first part of this series on quantum computing delved into the physics behind it. A quantum computer is not simply a faster version of a regular computer; it is a fundamentally different type of machine that begins with a very cold, very small loop of metal where particles behave in ways that they do not anywhere else on Earth. The second part explored what happens when this machine is directed at bitcoin. Bitcoin wallets rely on a one-way mathematical problem. Converting a private key into a public address takes milliseconds, but reversing the process, from public address back to private key, would take a regular computer longer than the age of the universe. A quantum algorithm known as Shor's algorithm reduces this gap. A recent paper by Google demonstrated that this attack could be carried out with significantly fewer resources than previously estimated, within a time frame that competes with bitcoin's block times. This final piece in the series focuses on the response. It examines what is actually at risk, what bitcoin has done to address the issue, and whether a network designed to resist coordinated change can implement the largest security upgrade in its history before the necessary hardware is developed. The pool of exposed bitcoin is substantial, with approximately 6.9 million bitcoin, or about one-third of all mined bitcoin, stored in wallets whose public keys are permanently visible on the blockchain. Most of this bitcoin is from the network's early years, stored in an address format that published the public key by default. It also includes any wallet that has ever been spent from, as spending reveals the key for whatever remains. A quantum attacker would not need to compete with an ongoing transaction. Instead, they could work through the wallets with already exposed keys at their leisure, one by one. Bitcoin's pseudonymous creator, Satoshi Nakamoto, holds roughly 1 million bitcoin, which has remained untouched since the network's early days and now falls into the exposed category. The 2021 Taproot upgrade expanded the problem. Taproot is a modification to how bitcoin addresses function, intended to make transactions more efficient and private. A side effect was that any bitcoin spent since Taproot's activation has published the key protecting whatever remains at that address. This was not an error but a reasonable trade-off at the time, when quantum timelines appeared much longer than they do now. Several initiatives are underway to address the quantum threat. Ethereum, which can be considered one of Bitcoin's largest competitors among institutional investors, has had a formal quantum-resistant program in place since 2018. The Ethereum Foundation operates four teams working full-time on the migration, with over ten independent developer groups releasing weekly test networks. The plan outlines specific upgrades across four upcoming network-wide changes, transitioning Ethereum's security to new mathematics that quantum computers cannot crack. It has even launched a dedicated website, pq.ethereum.org, to track its progress. Bitcoin does not have an equivalent strategy at this time. That does not mean there are no efforts to solve the issue. One formal proposal, BIP-360, from a group of developers and researchers, would introduce new quantum-safe address types that holders could voluntarily migrate to. A competing proposal from BitMEX Research would implement a detection system that triggers defensive action if a quantum attack is observed on the network. However, neither proposal has broad support from bitcoin's core developers, and they address different aspects of the problem. Nic Carter, a prominent bitcoin advocate, has highlighted the issue in recent months. "Elliptic curve cryptography is on the verge of becoming obsolete," Carter wrote, referring to the mathematics that secures bitcoin wallets. He described Ethereum's approach as "best in class" and bitcoin's as "worst in class," citing developers who "deny, gaslight, gatekeep, bury heads in sand" rather than engage with the problem. Adam Back, the CEO of Blockstream and a prominent early bitcoin contributor, disagrees on the urgency but agrees on the direction. "Quantum computing still has a lot to prove. Current systems are essentially lab experiments," Back said at a conference earlier this month. However, he also stated that bitcoin should prepare now, with optional upgrades built in advance so the network can migrate when needed, rather than scrambling in a crisis. The biggest challenge in implementing effective solutions against Bitcoin's quantum threat is coordination. Bitcoin's migration is more difficult than Ethereum's for reasons unrelated to the actual mathematics. Ethereum has a foundation that funds engineering work and a governance process that regularly passes major upgrades. Bitcoin has neither. Its development culture views any central authority as a failure mode, and its social consensus holds that changes to the protocol should be rare and difficult. These principles have kept the network stable for nearly two decades but also make the quantum problem structurally harder for bitcoin to solve. Migrating the 6.9 million exposed coins requires decisions the network has spent twenty years avoiding. Should old address formats be frozen after a certain date to protect coins from future theft? Should exposed coins be allowed to move to new quantum-safe addresses using their original keys? What happens to coins whose owners cannot or will not migrate? Satoshi's coins are the most striking example. Freezing old formats protects the coins from theft but makes them permanently inaccessible, including to Satoshi. Leaving the old formats open means those coins remain a standing prize for whoever builds the first working quantum computer or has access to a quantum computer and wants to attack. Setting a migration deadline forces Satoshi to either move the coins, revealing their ownership, or lose them. Every option changes bitcoin's character in ways the network has historically refused to change it. The Google paper's own framing is a summary of where the industry stands. A successful attack on the mathematics bitcoin uses "should not be seen as a wake-up call to adopt post-quantum cryptography as much as a potential signal that PQC adoption has already failed." This means that by the time the threat becomes visible, the window to respond may already have closed. Developers now face a question of whether a network built to resist coordinated change can coordinate the biggest security upgrade in its history before the hardware catches up to the theory. Ethereum's eight-year head start suggests the correct answer is to start now. Bitcoin's governance culture suggests the likely answer is to wait until the threat is demonstrated, then move. Only one of those answers works if the timeline turns out to be shorter than the optimists' estimate.