The brief exposure relates to the mempool, which serves as the holding area for unconfirmed transactions. While transactions linger there, waiting to be added to a block, your public key and signature remain accessible to the entire network.
A quantum computer could potentially access this information, but it would have a limited timeframe—before the transaction receives confirmation and gets buried beneath additional blocks—to determine the related private key and exploit it.
Proposals
BIP 360: Eliminating Public Key Exposure
As previously mentioned, each new Bitcoin address generated through Taproot currently exposes a public key on-chain indefinitely, presenting a constant target for future quantum computing attacks.
Bitcoin Improvement Proposal (BIP) 360 aims to eliminate the public key that is permanently visible on-chain by introducing a novel output format known as Pay-to-Merkle-Root (P2MR).
It’s important to remember that a quantum computer can analyze the public key, reverse-engineer the structure of the private key, and create a functioning copy. By removing the public key, the attack loses its basis. Meanwhile, all other functionalities, including Lightning payments, multi-signature configurations, and additional Bitcoin features, remain unchanged.
Nevertheless, if this proposal is enacted, it would only safeguard newly generated coins moving forward. The existing 1.7 million BTC already stored in older, exposed addresses represents a different challenge, which is addressed by other subsequent proposals.