Revisiting secp256r1 signatures (i.e. P256, mobile HSM support)

The conversation begins by acknowledging the challenges associated with this integration, including achieving community consensus and the technical hurdles of implementing a high-quality solution comparable to the current libsecp256k1 library. Despite these challenges, the dialogue underscores the potential benefits of P256 integration, such as improving the onboarding experience for new users, enhancing the security of hot wallets, and reducing costs associated with collaborative multisigs. However, concerns about the timing of such an integration are raised, considering the ongoing development of post-quantum cryptographic solutions that may shift the community's focus away from P256.

Further discussion delves into the WebAuthn standard's compatibility with Bitcoin's security needs, particularly in the context of hardware security modules (HSM) and post-quantum cryptography. The discourse suggests that researching how to adapt WebAuthn's signature formats for Bitcoin might offer a productive path toward ensuring long-term security and utility. Nonetheless, there are significant concerns regarding WebAuthn's suitability for Bitcoin, given its design for centralized web authentication and the lack of support for key features like deterministic backup seeds for user recovery and compatibility with hierarchical deterministic wallets.

In addition to exploring the technical and practical aspects of integrating P256 and WebAuthn standards into Bitcoin, the conversation also revisits historical apprehensions within the Bitcoin community regarding P256. These include fears over potential backdoors introduced by NIST, although such concerns have diminished over time. The argument for adopting P256 centers on its promise to enhance user experience and security, despite its slower validation times compared to secp256k1. The potential for P256 to enable secure access to platform APIs for HSMs on mobile devices is highlighted as a significant advantage, suggesting a compelling case for reevaluating P256 support within the Bitcoin ecosystem.

Concurrently, the discussion touches upon the apprehensions around reintroducing the OP_CAT vulnerability through the guise of secp256r1 support. This concern points to broader issues of security and the relevance of certain technical arguments to the core functionality and safety of the Bitcoin protocol. The mention of existing technologies like Samsung's Blockchain Keystore indicates that solutions for secure cryptocurrency management on mobile devices already exist, challenging the necessity and relevance of some proposed changes.

Overall, the exchange on the mailing list reflects a deep and multifaceted debate over the future of Bitcoin's cryptographic standards, balancing the need for advancement and compatibility with modern technologies against the imperatives of security, user autonomy, and the preservation of fundamental features that define the cryptocurrency. The discussion encapsulates a broad spectrum of viewpoints and considerations, from the technical specifics of cryptographic curves to the philosophical underpinnings of Bitcoin's design and use.