Quantum calculations are still a little bit away from the real threat of bitcoin, but progress is making this risk a reality from a long-term issue. The term “Q-Day” usually refers to the point where a quantum computer is strong enough to break the existing encryption system.

The wallet with the exposed public key is weaker.

Bitcoin signs with an elliptical curve. Most addresses do not disclose the complete public key before the first expenditure, but the public key will remain on the chain as soon as the transfer occurs. In earlier address formats, some public keys were made public even before the first expenditure.

This means that older wallets, reused addresses, early miners ' output and long-term sleeping accounts can be priorities for the future. It was mentioned that the size of assets already exposed to the public key could exceed $45.2 billion, including bitcoin in part of the bright age.

It's hard to identify at the time of the attack.

If a quantum attack does occur, the process does not necessarily have a clear warning. The assailant can first select the address where the public key has been exposed, then run the Shor algorithm using quantum calculations, reverse the release of the corresponding private key and use it to forge a valid signature to transfer the asset.

This type of transaction does not appear to be different in the chain from a normal transaction. Node will accept and miners may also pack it into blocks. If multiple high-value addresses are attacked at the same time, funds may be transferred in a short period of time, and the market response may be even faster than the event confirmed.

Google and policy moves to focus. degrees

Over the past year, progress in the area of quantum computing has clearly accelerated. The institutions Google, IBM, Microsoft and Caltech publish new developments in chips, logical quantum bits and error resolution. In March 2026, research papers by Google and Caltech further raised market concerns, as they suggested that future quantum resources needed to decipher the elliptical curve could be lower than previously estimated.

  • Coinbase established the Quantum Safety Advisory Board in January 2026
  • The US Department of Commerce announced $2 billion in May 2026.
  • Trump signed two quantum-related executive orders in June 2026.

France also indicated in June 2026 that the certification of technical products not considered to be quantum safety would be discontinued and that a direct link between the security certification and the back quantum password requirements would begin.

Bitcoin migration won't be done soon.

The real challenge lies in the fact that it takes years for Bitcoin to move to a later quantum signature system, even if it is now ready. Developers must not only design new programmes, but also facilitate the gradual migration of wallets, infrastructure and users.

The most difficult of these are those that have lost private keys or long-term uncontrollable addresses. The article cites the view that the size of such assets may be approximately $180 billion, a significant part of which is considered to belong to the Chinese-hearing age address. As no one has voluntarily moved, these currencies may remain under the old encryption system for a long time in the future.

The current consensus is not that quantum calculations can break bitcoin, but that preparation windows may not be as long as they used to be. After-quant signatures, address migration and compatibility programmes are being studied by developers, but community consensus on specific routes is still lacking.