BIP-352: Limiting the number of per-group recipients (K_max)

These issues are exacerbated in scenarios involving adversarial transactions, leading to the proposal of implementing a "K_max" protocol limit. This proposed limit aims to cap the maximum number of recipients per group in a single transaction, which, although marking a shift from existing protocols, is expected not to affect current Silent Payment wallets if the K_max value is set to a sufficiently high figure, such as 1000. The rationale and specifics behind this proposed change have been detailed in a draft Bitcoin Improvement Proposal (BIP), available for review here.

To facilitate community engagement and gather feedback on the proposed K_max protocol adjustment, various channels have been utilized for communication. Direct notifications were sent to SP wallet developers, and information was disseminated across developer mailing lists. This approach aimed at capturing insights and concerns from a broad audience to ensure that diverse perspectives and expertise are considered in refining the proposal. Interested parties are encouraged to contribute to the ongoing discussions and voice potential implications for existing or future wallet implementations through the GitHub issue link provided here.

Following the lack of objections to the proposed protocol change, a corresponding Pull Request (PR) has been opened in the BIPs repository to continue the discussion. This PR can be viewed and contributed to at this link, signifying an important step towards consolidating community feedback and furthering the development of the Silent Payments module in libsecp256k1. This process underscores the collaborative effort to address the performance challenges identified and enhance the overall functionality of Silent Payments within the Bitcoin ecosystem.