QRMVL: Modular Verification Layer for Post-Quantum Hash-Based Signatures

This method is favored as a safer, incremental step compared to an immediate shift to full quantum-safe (PQ) signature schemes. Commencing with a commit and reveal strategy is advantageous as it facilitates the evolution of a quantum-resilient vault mechanism alongside a covenant primitive, sidestepping early trust assumptions. Additionally, this approach allows the ecosystem ample time to refine a performance-optimized library dedicated to quantum-safe commitments, preparing for a more intricate transition to PQ signatures. This cautious progression is contrasted against the haste in moving directly towards full PQ signatures, considering the current developmental maturity of quantum-safe signature libraries relative to established cryptographic standards like secp256k1, which have been optimized extensively against vulnerabilities such as timing side channels.

Parallel to these discussions, a novel framework named Quantum-Resilient Modular Verification Layer (QRMVL) has been introduced, aimed at addressing verification bottlenecks and scalability challenges posed by hash-based PQ signatures within Bitcoin's infrastructure. QRMVL proposes a soft-fork-compatible, gradual pathway towards PQ validation while maintaining existing validation semantics. The framework encompasses hybrid hash-based signatures, integrating both stateful and stateless components, and introduces a STARK-style Linear Hash Tree (LHT) for efficient Merkle verification. It also features a deterministic UTXO-bound index to prevent state-reuse issues and designs a fail-fast node pipeline to minimize PQC Denial-of-Service (DoS) exposure. Moreover, QRMVL suggests tiered P2PQS levels to cater to varying security needs and ensures full backward compatibility with witness extensions without altering transaction identifiers (txid).

To further develop QRMVL, feedback is sought on several fronts including the practicality of implementing a soft-fork activation path, implications on script versioning and witness layout, mempool policy adjustments for PQ witness sizes, risks entailed by deterministic LMS index derivation, and the potential impact on Initial Block Download (IBD) and low-power validation hardware. The community's input is deemed crucial for refining specifications and ensuring the framework's alignment with user requirements and technical constraints. For those interested in delving deeper into the QRMVL framework or contributing feedback, resources such as the draft whitepaper and a repository containing examples and pseudocode are available at https://github.com/karinCrypto/bitcoin-quantum-scaling/blob/main/whitepaper/QRMVL%20v1%20A%20First%20Edition%20Framework%20for%20Quantum-Resilient%20Verification%20in%20Bitcoin_.pdf and https://github.com/karinCrypto/bitcoin-quantum-scaling.