Hashed keys are actually fully quantum secure

The discussion across the Bitcoin Development Mailing List highlights a proactive approach to addressing potential threats from quantum computing (QC) to Bitcoin's security. The strategy involves the possibility of implementing a soft fork that would disallow the spending of bare public keys, thereby mitigating the risks associated with quantum computing attacks without requiring immediate action from users. This idea leverages the inherent security benefits of Taproot keys, which are technically hashed keys, offering a more secure alternative to traditional public key exposure.

Taproot keys present a significant advantage in this context as they do not reveal the internal key even when used for external spends, unlike other methods that might expose public keys through address reuse. This characteristic of Taproot keys is pivotal in reducing vulnerability to QC attacks since it ensures that the internal key remains undisclosed. In anticipation of a QC threat materializing, users are advised to transition to Taproot wallets, a move that simplifies protection against such threats while minimizing user confusion that could arise from recommendations to revert to p2pkh addresses. The concern here is that p2pkh addresses, while seemingly secure, may already have exposed public keys due to past transactions or address reuse, thus compromising their security in the face of QC.

Furthermore, embedding the QR signature scheme within a Taproot leaf before its activation is proposed as a means to prepare for QR spending paths, ensuring readiness for a transition without necessitating immediate actions by users. This approach underscores the importance of normalization of Taproot addresses to streamline the process.

The challenge extends beyond the technical realm into achieving social consensus on when to trigger the protective soft fork. The timing is delicate; it must occur after it becomes evident that constructing a secp256k1 DLOG QC is possible but before such a computer is actually built. This preemptive action complicates the situation due to the current uncertainty surrounding the feasibility of constructing a QC capable of threatening Bitcoin's cryptographic foundation. Furthermore, there's an acknowledgment of the potential for malicious actors to influence the decision-making process regarding the timing of the soft fork, either by delaying or precipitating its implementation.

This dialogue reflects a nuanced understanding of the intersection between technology and community consensus in safeguarding Bitcoin against emerging threats, emphasizing a strategic rather than reactionary posture towards quantum computing challenges.