Proposal: OP_STARK_VERIFY - Native STARK Proof Verification in Bitcoin Script

This initiative aims at enabling a range of applications from Validity rollups and post-quantum signatures to privacy-preserving transactions, leveraging the advantages of STARK (Scalable Transparent ARgument of Knowledge) proofs. These proofs are favored for their transparent, post-quantum secure assumptions, and their poly-logarithmic verification complexity coupled with sublinear proof sizes, making them particularly attractive for scaling Bitcoin's Layer 1, enabling signature aggregation, and facilitating shielded transactions.

However, the proposal acknowledges substantial challenges, including the issue of credible neutrality in selecting a specific STARK protocol, the inherently large proof sizes when compared to other systems like SNARKs, and the technical and consensus risks associated with embedding a specific proof system directly into Bitcoin's consensus layer. Alternative verification methods such as OP_CAT-based verifiers and arithmetic opcodes are discussed for comparative analysis, demonstrating various trade-offs in efficiency, flexibility, and the degree of protocol enshrinement.

The exploration further delves into the nuances of implementing STARK proofs within Bitcoin, highlighting the intricate balance between proving speed, proof size, and verification efficiency. The discussion emphasizes the technical considerations involved in optimizing these parameters through a multistage pipeline designed to process and compress proofs for verifier-friendly interaction. This detailed examination sheds light on the computational strategies and on-chain cost implications of different proof compression methodologies.

An alternative approach to integrating ZK verification into Bitcoin is proposed via a metaprotocol layered over Bitcoin, which would utilize existing witness space for embedding STARK proofs while managing verification and system state off-chain. This method aims to mitigate risk by avoiding direct alterations to the Bitcoin base protocol, fostering market-driven adoption without necessitating contentious soft forks, and allowing for the evolution of competing proof systems.

Despite acknowledging the potential of metaprotocols and the proven track record of technologies like Starknet on other platforms, concerns are raised regarding the security and practical application of cryptographic proofs in permissionless exits from multiparty systems. The discussion highlights vulnerabilities in the current methodology that could allow misuse of proofs across unauthorized transactions. Proposed solutions involve incorporating public parameters or utilizing Schnorr signatures to tightly couple proofs with their intended transactions, enhancing security and integrity within the blockchain ecosystem.

In conclusion, while the integration of OP_STARK_VERIFY presents a forward-thinking approach to augmenting Bitcoin's capabilities, it also surfaces significant questions about maintaining the protocol's core principles of simplicity, security, and stability. The discussion underscores the importance of cautious consideration regarding the irreversible risks of embedding complex, specific systems into Bitcoin's consensus layer and suggests a preference for retaining such complexity within higher layers or adopting more generic, composable primitives to preserve adaptability and future-proofing against evolving cryptographic advancements.