Jim Cramer to sell Bitcoin after IBM CEO's 3-year quantum warning

Bitcoin traded at $63,808 as Jim Cramer said he would sell Bitcoin after IBM's CEO warned of a quantum threat in three to four years.

"I think that you should give yourself three or four years, and at that point, I would get rather paranoid about it," Arvind Krishna, chief executive at IBM, said during a July 31 interview on CNBC's Mad Money.

Cramer, who hosts Mad Money, said on Aug. 3 he would sell his Bitcoin, telling viewers "I am going to sell my Bitcoin." He added that he trusted Krishna's assessment because "he knows Bitcoin and quantum." The size of Cramer's holdings was not disclosed. Galaxy Digital pledged up to $5 million on July 21 to help strengthen Bitcoin's resistance to future quantum attacks, the asset manager said.

The threat centers on Bitcoin's elliptic curve digital signature algorithm, or ECDSA, which verifies ownership when coins are spent. A sufficiently powerful quantum computer could work backward from a wallet's public details to recover its private key. About one-third of existing Bitcoin has public keys exposed on the blockchain, creating a target for future attacks, while estimates of when such a machine could emerge range from five years to Blockstream chief executive Adam Back's 20-to-40-year forecast.

The cryptography at risk

Bitcoin's mining and ledger run on SHA-256, a hash function that quantum computers cannot efficiently break, meaning no attacker could rewrite the chain's history or mine all remaining coins at once. The vulnerability sits in ECDSA, the digital signature system used to prove ownership. A quantum computer could theoretically use a wallet's publicly exposed information to calculate its private key and drain the coins inside.

The exposure is concentrated. Roughly one-third of all Bitcoin already has public keys visible on the chain, including the roughly 1.1 million BTC believed to belong to pseudonymous creator Satoshi Nakamoto, a substantial share of the 21 million-coin maximum supply.

Proposals and the consensus problem

Bitcoin developers have floated two improvement proposals. BIP-360 would introduce a new address type designed to protect coins against quantum attacks, but it would not automatically secure older wallets whose public keys are already exposed. BIP-361, far more contentious, would retire coins tied to older signatures after a five-year transition period, a move critics say would override the property rights of dormant holders.

The technical fix already exists — quantum-resistant cryptography is available today. The harder challenge is getting Bitcoin's decentralized developer and user community to agree on how and when to implement it. Google researchers said in March that advances could reduce the hardware required to attack Bitcoin's cryptography by roughly 20-fold compared with earlier estimates, though the technology remains years from practical deployment.

The quantum threat has already entered mainstream risk disclosures. BlackRock's iShares Bitcoin ETF lists it among risks, and Ethereum researchers are targeting a transition to quantum-safe cryptography later this decade. For now, no known quantum computer can break Bitcoin's ECDSA protection, and the market has shown little reaction — Bitcoin was up 0.49 percent over 24 hours as of the Aug. 3 broadcast.

This article is for informational purposes only and does not constitute investment advice.