S15 E17: Andrew Poelstra on Covenants (OP_CAT vs OP_CTV)
Feb 2, 2024
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Andrew Poelstra, mathematician and head of research at Blockstream, discusses covenants in Bitcoin Script, including op CAT and op CTV. The chapter explores the functionalities of op codes dupe and cat, the limitations of CTV, and the potential solution of CAT for more flexible transactions. They also discuss personal experiences with Wasabi and JoinMarket, the integration of Wasabi and Shop N Bit, and the future improvements needed in Bitcoin.
Op Cat enables the creation of covenants, adding security and flexibility to Bitcoin transactions.
Op Cat is a potential next soft fork in Bitcoin, with larger covenant proposals expected to follow.
Mimblewimble extension blocks have not gained much traction in Bitcoin, with focus on Op Cat and covenants instead.
Deep dives
Op Cat and covenants
Op Cat is a powerful opcode that allows users to concatenate and split data in Bitcoin script. It enables the creation of covenants, which are controls over where coins can be moved. One example is the use of vaults, where coins are required to sit in a staging area before being moved to their final destination. This provides additional security against theft. Another example is in the efficient withdrawal of coins from exchanges, where users can choose when and at what fee rate to claim their coins. While Op Cat is a small and simple addition, it is seen as an important step towards enabling covenants in Bitcoin and improving the flexibility and control users have over their funds.
The Next Soft Fork and Upcoming Proposals
Op Cat is likely to be the next soft fork in Bitcoin, with its small code size and potential benefits for users. It is seen as a way to flex the soft fork deployment process, but a larger covenant proposal is expected to follow. Proposals like CTV, Ellen Hance, or TX Hash could be potential candidates for a future soft fork, enabling more complex and powerful covenants in the Bitcoin protocol. While these changes may introduce some drama and technical challenges, they offer tangible benefits for users such as improved custody solutions and more efficient fee management.
Litecoin's Mimblewimble Extension Blocks
The implementation of Mimblewimble extension blocks in Litecoin back in 2016 generated excitement, but the idea hasn't gained much traction in the Bitcoin space. Mimblewimble extension blocks allow for privacy enhancements and improved scalability by compressing transaction data. However, in Bitcoin, there hasn't been significant push or development towards implementing this technology despite its successful implementation in Litecoin. The focus in Bitcoin has been on other proposals and improvements such as Op Cat and covenants.
Summary of Main Points
In this podcast episode, the speaker discusses various topics related to Bitcoin, including the implementation of soft forks like Taproot and Cat.Op and the challenges involved in introducing new features. The speaker explains that Cat.Op is a simpler and safer alternative to CTV (Controlled Time Value), providing a scripting capability without the need for extensive cryptography. They highlight the technical aspects of Cat.Op, such as its small code footprint and its ability to perform hash challenges, making it suitable for lightning and other applications. The speaker expresses concerns about drive chains and extension blocks, stating that they can potentially disrupt the incentive structure of miners and pose risks to the integrity of the Bitcoin network.
Andrew's Work and Social Media Presence
To follow Andrew's work, one can check Blockstream Research's Twitter feed at BLKResearchxfeed. Andrew is also active on GitHub with the username apolstra. While he does not use mainstream social media platforms, he can be found on IRC with the username AndyToshi, where he engages in discussions related to Bitcoin and cryptography.
Personal Experiences with Wasabi and JoinMarket, Integration of Wasabi and Shop N Bit, Discussion on Covenants and Benefits for Businesses and Developers
Andrew Poelstra is a mathematician who heads the research department at Blockstream. Over the years, he experimented with many Bitcoin OP codes – some of which are also enabled on Liquid. In this episode, he explains why he likes and prefers OP_CAT.
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