Key Points
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Bitcoin is the biggest cryptocurrency.
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If it becomes compromised by a quantum computer, it would be a weaker investment than coins that are secure.
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A few of the crypto majors are ahead of the game in planning for that possibility.
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Today, Bitcoin (CRYPTO: BTC) has a market cap of $1.6 trillion, making it the biggest cryptocurrency and also one of the biggest assets in the world. That might not be the case within five years: Ethereum (CRYPTO: ETH), Solana (CRYPTO: SOL), or Zcash (CRYPTO: ZEC) could be worth more. But as of Nov. 4, none of those coins were worth even 20% of it.
Closing a market cap gap that large will take some serious problems for Bitcoin and also a few important victories for the contenders. Here is one scenario to consider.
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Bitcoin’s quantum problem could be a major drag, and sooner than anticipated
Theoretically, a powerful enough quantum computer could crack Bitcoin’s encryption and enable the theft of users’ funds. No such computer exists today. However, in March 2026, Google’s Quantum AI division estimated that breaking Bitcoin would be substantially easier than previously believed, and it wasn’t the first to suggest this.
Crypto experts believe that over 34% of all Bitcoin could be vulnerable to this kind of attack, and the coin’s value would take serious punishment if a quantum attack were ever confirmed. That punishment would also hit the institutions holding it through spot Bitcoin exchange-traded funds (ETFs).
There are a few plans to patch Bitcoin’s blockchain to guard against quantum risk, but they’re still in draft form and are highly controversial among the Bitcoin developer community. The authors of one such plan, called BIP-361, say that implementing it would take five years, and even starting that process would require a lot of consensus building that is only getting started.
In contrast, Bitcoin’s challengers have clearer timelines for mitigating the quantum threat, though none of their plans are finished yet, either.
The Ethereum Foundation is planning to have core quantum protections in place by about 2029. Solana’s developers chose a quantum-resistant signature scheme in April 2026, an important precursor to immunizing their blockchain, though they still have no plans to make near-term changes. At the front of the pack are Zcash’s developers, who aim to start protecting some transactions from quantum attacks by January 2027.
So the basic conditions for a scenario in which one of those coins surpasses Bitcoin’s value in the next five years are that quantum computing continues to become more sophisticated in terms of the available hardware, the available quantum code-breaking algorithms, and the possible attack routes. As a result of either a quantum computing breakthrough or an actual quantum attack on Bitcoin, the market could flee the cryptocurrencies that are thought to be insecure and instead pile into whatever safe havens exist.
Which coin is best positioned?
Widespread fear of Bitcoin being compromised by a quantum attacker probably wouldn’t, in itself, be enough for one of its competitors to surpass it in value. That competitor would also need better economics for holders and a stronger investment thesis, not to mention a decent track record of delivering on its stated objectives.
Zcash is currently in the lead on that front. Its supply policy is largely a copy of Bitcoin’s 21-million-coin supply cap, so it can also serve as a scarce store of value. And, starting on Nov. 5, its NU7 upgrade will remove 60% of each block’s crypto transaction fees from circulation until about February 2031, when the removed coins will be used to pay miners.
In October, Ethereum shelved a plan to slow the creation of new coins, while Solana’s community voted to slow its own coin creation, though that change hasn’t taken effect yet.
But neither coin has a supply cap, which means both see their supplies inflate slowly over time. So for either one to have a strong shot at becoming larger than Bitcoin, its ecosystem would need to take off and generate a huge amount of activity, and it would have to implement more supply reforms.
So the most likely outcome is that none of these coins will pass Bitcoin by 2031.
Still, of the contenders, Zcash has the best chance, given its early start on quantum defenses and the similarities that it already shares with Bitcoin.
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Alex Carchidi has positions in Bitcoin, Ethereum, Solana, and Zcash. The Motley Fool has positions in and recommends Bitcoin, Ethereum, and Solana. The Motley Fool has a disclosure policy.
