Hashed keys are actually fully quantum secure

In a recent exchange on the Bitcoin Development Mailing List, an intriguing discussion unfolded concerning Taproot's hashing and its implications for security and usability within the Bitcoin framework. The conversation highlighted the unique aspect of Taproot that, despite disallowing spending with a null tweak, still facilitates the creation of a proof similar to previously suggested methods. This characteristic of Taproot opens up a nuanced perspective on address reuse. Contrary to common beliefs around the pitfalls of address reuse, it was pointed out that with Taproot, this practice might not pose as significant of an issue as it does with other protocols.

The dialogue further delved into the intricacies of implementing QR signature schemes in tapleaf scripts. One critical point raised was the necessity for these schemes to be predefined, which currently presents a challenge due to the absence of consensus on which scheme is most suitable. This predicament underscores a broader flexibility concern within Taproot, suggesting that there may need to be more time allocated to thoroughly vet and decide on the most effective and secure implementation strategies.

Moreover, the discussion ventured into a comparison between Taproot and traditional pay-to-pubkey-hash (p2*pkh) mechanisms, focusing on their relative safety. A compelling argument was made against measuring Taproot's security through the lens of historical coin losses. Such losses, while impactful, do not directly equate to a systemic failure that would render Bitcoin valueless but rather influence market dynamics by altering the perceived value of the cryptocurrency. This distinction is crucial in understanding the real-world implications of security breaches within these systems. The conversation underscored the importance of individual practices, such as avoiding address reuse, in maintaining security. However, it also acknowledged the varying degrees of success individuals have with such practices, highlighting the complex social dynamics at play in the realm of cryptocurrency security.