[bitcoindev]

A new version, v2.1, of the co-signer spending policies draft has been published, presenting several key updates and improvements relevant to multi-signature policy specification in Bitcoin. The draft is accessible on GitHub, and further technical discussion can be found at Delving Bitcoin. Among the primary enhancements are the implementation of fail-closed policy validation, explicit field requirements, and a revised commitment structure that prioritizes version-first identification for CSP (Co-Signer Policy) and its associated commitments.

Additional contributions address aspects such as signed statement finality, which ensures that once a statement is signed it cannot be altered, as well as the introduction of mechanisms for finality-aware evidence and escrow procedures. The treatment of exact-byte vectors remains an open issue pending further clarification. Corrections have also been made to the k-of-n safety condition, along with updates to citations and document headers for improved clarity and accuracy.

Despite these advancements, some significant areas remain unresolved, including the decision between JSON and TLV for data serialization, the completion of the wire schema, and the provision of a reference implementation. Community feedback and further critique are actively solicited to refine and finalize the proposal.