It is not hard to find cases where bitcoin's price hits a record high and then immediately plunges. On Dec. 5 last year, it surpassed $100,000 for the first time, but it began to fall the next day and dropped to $95,000. In Aug., after hitting an all-time high of $124,000, it fell 13% over two weeks.
There were various reasons for the price drop, including selling pressure from profit-taking. But in just those two cases, some analysis pointed to quantum computers. Google announced the launch of its next-generation quantum computer chip "Willow" in Dec. last year, and IBM announced a quantum supercomputing development plan in Aug. The idea is that when there is positive news for quantum computers that could hack bitcoin in the future, bitcoin's price goes down.
Doubts about cryptocurrency security are growing as quantum computers advance. Anatoly Yakovenko, the founder of Solana, which has risen to No. 6 in market capitalization in the virtual asset market, said at the "All-in Summit 2025 conference" on the 18th that there is a 50% chance quantum computer systems will become strong enough to threaten bitcoin security within five years. Deloitte, one of the world's top consulting groups, also analyzed that 4 million bitcoins, or 25% of all bitcoins, are vulnerable to quantum attacks.
Owners of virtual assets such as bitcoin store their assets in wallets. When a wallet is created, a "private key" is generated that functions as a password. It is analogous to opening an account (wallet) at a bank and setting a password (private key).
The difference is that an "elliptic curve cryptography" is applied to the private key to create one more "public key." As the name suggests, a public key is made accessible to anyone. If the private key is a password known only to the virtual asset owner, the public key serves to verify the authenticity of a virtual asset transaction.
If Mr. A wants to send bitcoin to Ms. B, Mr. A signs with the private key, the password, saying "send 1 bitcoin to Ms. B's wallet." The network automatically uses Mr. A's public key to verify that the signature is genuine, and if it deems there is no issue, it records the data in the bitcoin ledger (blockchain) that "Mr. A sent 1 bitcoin to Ms. B."
In the bitcoin transfer process, the core of security is the private key. Because virtual assets can be sent with the private key, if only the private key is hacked, all stored virtual assets can be stolen. But with current technology, it is impossible. That is because one would have to compute backward from the public key to obtain the private key. While it is easy to create a public key by applying elliptic curve cryptography to a private key, it is difficult to compute backward from the public key to find the private key. It is like how it is easy to find the product of 23 and 71, but it takes time to reverse-calculate which two numbers multiply to 1,633.
In particular, cryptocurrencies use very large numbers with more than 1,000 digits, not four digits. Rather than being an unsolved mathematical conundrum, it is a task that takes time because each possibility must be checked and computed. For this reason, it is said that even if a supercomputer were used to hack a private key and steal bitcoin, it would take an unimaginably long time.
But the emergence of quantum computers has changed the situation. According to Google, the Willow quantum computer chip can solve in five minutes a problem that would take the fastest current supercomputer 10 to the 25th power (10 septillion) years. As quantum computers continue to advance, claims have begun to emerge that hacking bitcoin, which would otherwise take an infinite amount of time, could become possible.
However, the consensus is that current quantum technology has limits. To hack a private key in a day would require 13 million qubits (the basic unit of quantum information), while Willow is at the level of 105 qubits. The virtual asset industry does not see quantum as an imminent major threat, as developers are considering various countermeasures, such as creating new encryption algorithms in preparation for quantum technology.