IBM chief’s quantum warning reheats scrutiny of Bitcoin’s exposed legacy supply
Jim Cramer's vow to sell Bitcoin over quantum fears puts fresh focus on the 9.6% of BTC supply flagged as cryptographically exposed.
Bitcoin traded near $63,700 on 4 August, up around 1.6% on the day, after CNBC host Jim Cramer said he intended to sell his holdings on concerns that quantum computing could eventually undermine the network’s cryptography. The remarks, made in response to comments from IBM chairman and chief executive Arvind Krishna, have reignited a long-running debate over the timeline for so-called “cryptographically relevant” quantum machines and their implications for digital asset custody.
An IBM warning with a three-to-four year horizon
Krishna told CNBC that investors should become “paranoid” about cryptocurrency security within three to four years, a comment Cramer cited directly when announcing his intention to exit his position. “I’m going to sell mine,” Cramer said. Neither the size of his holdings nor any evidence that a sale has actually taken place has been disclosed.
IBM’s own published roadmap is more conservative than the tone of Krishna’s warning suggests. The company’s large-scale, fault-tolerant system, named Starling, is targeted for 2029 and is designed around 200 logical qubits capable of roughly 100 million quantum operations. IBM has not claimed that Starling, once built, would be capable of recovering Bitcoin private keys.
Google’s tightened estimate and Glassnode’s exposure count
The broader technical debate has been shaped by Google Quantum AI, which in March revised its own estimate of the hardware needed to break the elliptic curve cryptography underpinning Bitcoin and much of the wider digital asset ecosystem. Under its stated assumptions, fewer than 500,000 physical qubits could eventually be sufficient — a figure roughly 20 times lower than earlier calculations. Google described this as a future risk rather than a present capability, and has urged blockchain developers to begin migrating toward post-quantum cryptographic standards ahead of any such breakthrough.
On-chain analytics firm Glassnode has already attempted to quantify the scale of the potential exposure. Its May analysis classified 1.92 million bitcoin, equivalent to 9.6% of issued supply, as structurally vulnerable to a future quantum attack — largely coins sitting in older address formats that expose public keys directly on-chain. For institutional custodians and treasury allocators, that figure represents a live risk-management question long before any quantum machine capable of the attack actually exists.
Price holds range as market absorbs mixed signals
Bitcoin’s reaction to Cramer’s comments was muted. The asset moved between an intraday low near $62,387 and a high of $64,117 before easing back, leaving it broadly within the trading band that has held since June’s decline. Support has clustered near $60,000, with resistance in the $65,000 to $67,000 region; trading volume of roughly 5,950 BTC was comparatively modest against earlier selloff periods, suggesting the bounce lacked strong conviction.
The market was also digesting other developments, including Strategy’s recent share sale, estimates of miner distribution, and the fallout from the Coldcard security incident. Separately, a transfer of roughly 16,400 bitcoin — worth close to $1 billion at current prices — moved between wallets without landing on any identified exchange, a pattern typically read by analysts as custodial reshuffling rather than an imminent sell order.
For now, quantum risk to Bitcoin remains a forward-looking engineering problem rather than an active threat, but the exposure figures published by Glassnode and the tightened hardware estimates from Google are likely to keep post-quantum migration on the agenda for custodians, exchanges and institutional holders well before any machine capable of the attack is built.
Read more: Coldcard drain nears $89m, reviving debate over Bitcoin self-custody risk
