[BIP Proposal] OP_TWEAKADD

This opcode, suggested as part of an OP_SUCCESSx upgrade, emphasizes simplicity and efficiency in blockchain operations. The primary design considerations for OP_TWEAKADD include opting for push semantics over verification to streamline data on-chain, prioritizing the arrangement of arguments with the key on top for ease of tweak application in witness data, and choosing plain tweaks for flexibility, allowing users the option to hash if needed. This approach is seen as most adaptable, with the possibility of future enhancements to incorporate TapTree opcodes for constructing taproot tweaks. For further details, the draft BIP writeup can be explored at GitHub.

Among the notable examples left out of the main BIP discussion but mentioned later include the use of OP_TWEAKADD in combination with other proposed opcodes like OP_CSFS and OP_IKEY for tweak reveal scripts. These tweaks can facilitate various functionalities such as proof-of-signing-order, where one signature is bound and committed to another, ensuring transaction refinement. Additionally, delegation scenarios are covered where one key signs a message tweaked by another key, thus allowing for limited sighash mode operation. Another application is the Target Tweak, demonstrating the knowledge of a tweak that satisfies specific elliptic curve mathematics, essential for Taproot output disclosure or presence indication. Lastly, the Key Reveal example uses the Target Tweak concept to prove the knowledge of a discrete logarithm, showing the potential of OP_TWEAKADD in creating flexible, secure, and efficient cryptographic contracts within the Bitcoin protocol.

These examples collectively underscore the versatility of the OP_TWEAKADD opcode in enhancing Bitcoin’s scripting capabilities, offering insights into how it could improve transaction privacy, security, and flexibility. As the conversation around this proposal continues, feedback from the development community will be crucial in refining its implementation and integration into the broader Bitcoin protocol.