CTV + CSFS: a letter

The ongoing discussion within the Bitcoin development community, specifically concerning the TXHASH proposal and its implications for future protocol upgrades, highlights a multifaceted debate on the direction of Bitcoin's technological evolution. The TXHASH proposal, as articulated by one of its signers and authors, has sparked considerable interest and controversy, underscoring the community's desire for Core contributors to prioritize and deliberate on this proposition with urgency. This request comes from a place of seeking constructive engagement rather than confrontation, aiming to integrate Core contributors more closely into the conversation about potential protocol enhancements.

Notably, the TXHASH proposal is still in its nascent stages, lacking the extensive review and engagement initially anticipated by its proponents. Despite this, the proposal has been recognized for its innovative approach, though it necessitates further scrutiny and consideration due to its opinionated design. Such an opcode, which significantly alters transaction handling, invites a broader discussion on its implementation specifics, including the possibility of introducing similar semantics through a top-level sighash flag system, referred to as TXSIGHASH. This concept has been explored through simulations, offering insights into how it could facilitate fee sponsoring and stacking, as detailed in a comprehensive analysis available at DelvingBitcoin.org.

Moreover, the dialogue surrounding TXHASH touches upon the broader potential for innovation within the Bitcoin ecosystem. The introduction of templating and rebindable signatures, as exemplified by developments like BitVM and Ark, represents a significant step forward in enabling new use cases and functionalities. These advancements are not limited to specific applications but serve as foundational building blocks that can spur further innovation and improvement across the network.

In addition to TXHASH, there is ongoing consideration of other opcodes, such as CSFS and CTV, which are viewed as less contentious and more straightforward in their design. These proposals aim to enhance transaction id stability and provide a groundwork for future advancements, including those enabled by TXHASH. Despite the anticipation of TXHASH, there remains a recognition that demand for simpler variants like CTV/TEMPLATEHASH will persist, given their intuitive appeal and practical benefits for certain developers and applications.

The discourse also acknowledges concerns related to modifying legacy script elements and the necessity of optimizing for rebindable signature use cases. Proposed adjustments, such as replacing CTV with a TEMPLATEHASH opcode and introducing an INTERNALKEY opcode, reflect a willingness to adapt and refine the proposal based on community feedback and technical considerations. These suggested changes emphasize a pragmatic approach to evolving Bitcoin's scripting capabilities while minimizing contention and facilitating consensus within the developer community.