The long-term security of the Bitcoin network is under scrutiny from tech billionaires and crypto enthusiasts, who are questioning its resilience against quantum computing threats. However, former Mt. Gox CEO Mark Karpelès contends that the primary challenge isn't a direct quantum attack on the network's core hashing but rather the immense logistical hurdle of successfully upgrading every user to quantum-resistant standards. Karpelès recently warned on X (formerly Twitter) that such a comprehensive migration of the entire Bitcoin supply would span years and likely prove impossible to achieve 100% completion.

This critical distinction was highlighted when Tesla and SpaceX CEO Elon Musk prompted his Grok AI chatbot to assess the probability of Bitcoin's SHA-256 hashing algorithm being compromised by quantum computers by 2035. Grok estimated the risk at less than 10%, concluding that Bitcoin was safe "for now." Karpelès quickly interjected, pointing out that Musk and his AI were misidentifying the vulnerable component. He clarified that while SHA-256, used for mining, is highly resistant to quantum attacks, the digital signatures used to authorize Bitcoin transactions, specifically ECDSA (Elliptic Curve Digital Signature Algorithm), are not.

The real threat to Bitcoin's integrity stems from the potential for a fault-tolerant quantum computer, employing Shor's algorithm, to reach a sufficient scale. Such a machine could theoretically derive a user's private key from their exposed public key. This capability would enable an attacker to forge digital signatures, thereby allowing them to steal funds by authorizing fraudulent transactions on the network.

Addressing this vulnerability presents a significant migration nightmare for the Bitcoin ecosystem. While Bitcoin developers could theoretically introduce new post-quantum signature schemes via a soft fork, deploying the updated code is merely the first step. As Karpelès explained, "Bitcoin will need to not only upgrade its cryptography but also have everyone using the current cryptography by moving their coins to new quantum-safe addresses." He emphasized that this monumental task would likely require years and would never achieve full completion across all users.

A unique vulnerability exists with early Bitcoin addresses, particularly those using the P2PK (Pay-to-Public-Key) script, where public keys are directly exposed on the blockchain by design. The owners of lost or dormant coins associated with these addresses cannot manually move them to new quantum-safe addresses, leaving these funds entirely exposed to potential quantum theft. Karpelès starkly warned, "At some point, untouched coins will have to be locked... This is not going to be an easy migration."

The suggestion of locking or "burning" these vulnerable coins at the protocol level, while potentially preventing a massive market dump by a quantum thief, introduces a profound dilemma. Such a measure would fundamentally violate Bitcoin's core tenets of immutability and absolute property rights. Despite this, Karpelès believes the network will ultimately be forced to confront this difficult choice. He concluded, "Locking will not be happening at first, but considering it's impossible for 100% of coins to be moved (especially Satoshi coins), only options will be either letting an attacker take ownership or lock. Not a question of if but when."