Changes to BIP-360 - Pay to Quantum Resistant Hash (P2QRH)

The primary adjustment involves transitioning from Pay to Quantum Resistant Hash (P2QRH) to a script-only version of Taproot (P2TR), effectively removing pathways vulnerable to quantum attacks. This change ensures that P2QRH outputs are directly committed to the tapleaf merkle root computed by taproot, thus enhancing security. The scriptPubKey for P2QRH has been defined as OP_PUSHNUM_3 OP_PUSHBYTES_32, indicating this update. These adjustments utilize the existing taproot infrastructure, which simplifies implementation and enhances protection against long-exposure attacks—those expected to be viable before short-exposure ones.

Moreover, BIP-360 introduces a forward-looking strategy concerning Post-Quantum (PQ) signatures, separating their specification from the BIP to allow independent consideration and development. An informational section suggests incorporating tapscript PQ signature verification opcodes for various algorithms through OP_SUCCESSx opcodes. This method extends flexibility in activating PQ signature algorithms and sets a blueprint for future integration without requiring new tapleaf versions. A comprehensive specification for these PQ signatures is slated for a forthcoming BIP.

The discussion around the naming and conceptual framing of the proposal highlights a shift in focus from solely quantum resistance to broader applicability across different ecosystem segments. Suggestions for renaming the proposed soft-fork to either pay-to-tapscript (p2ts) or pay-to-mast reflect a preference for terminology that captures its broad utility rather than being narrowly quantum-specific. Further discussions emphasize the importance of clear, user-friendly labeling strategies like Segwit version 3, which incorporates an 'r' to signify resistance (e.g., bc1r.), aiding users in identifying quantum-resistant addresses and preventing losses due to quantum advancements.

Critiques of the terminology "pay-to-quantum-resistant-hash" argue that it might miscommunicate the proposal's intentions and mechanics, suggesting a possible hindrance to immediate interest and adoption until quantum threats become more imminent. There are also concerns about the practical implications of using specific letters in addresses to indicate quantum resistance, potentially setting a confusing precedent not aligned with current standards or expectations for address formatting.

These discussions underline a broader apprehension regarding the utility and timing of adopting technological advancements predicated on speculative future threats. The suggestion to rename the concept to "Pay to Tap Script Hash" or P2TSH shows a playful yet strategic approach to gaining approval within the community, reflecting interpersonal dynamics and creative persuasion alongside the technical aspects of proposing improvements within the Bitcoin ecosystem.

In summary, the evolution of BIP-360 reflects both technical advancements and strategic considerations aimed at preparing Bitcoin's infrastructure for future quantum computing challenges while ensuring broad applicability and ease of integration within the current ecosystem.