Concept Review: B-SSL (Bitcoin Secure Signing Layer) — Covenant-Free Vault Model Using Taproot, CSV, and CLTV

Francesco Madonna introduces a novel vault construction concept titled B-SSL — Bitcoin Secure Signing Layer. This design is aimed at self-custody solutions, specifically addressing the issue of permanent key loss while ensuring the enforceability of transactions directly on the blockchain. The B-SSL leverages existing Bitcoin technologies such as Taproot, CHECKSEQUENCEVERIFY, and CHECKLOCKTIMEVERIFY to create a secure framework. It outlines three distinct spending paths to facilitate user-initiated transactions, fallback recovery, and custodian recovery or inheritance protection. These paths are defined as follows: a user-initiated path that can be activated after a delay ranging from 2 hours to 15 days using CHECKSEQUENCEVERIFY (CSV), a fallback recovery path accessible after 1 year with CHECKLOCKTIMEVERIFY (CLTV), and a custodian recovery or inheritance safeguard available after 3 years, also through CHECKLOCKTIMEVERIFY.

A significant aspect of the B-SSL architecture involves mirrored backups labeled A₁ and B₁ for keys A and B, enhancing the security and redundancy of the system. An optional feature of this concept is the "Convenience Service" (CS), an off-chain mechanism designed to implement delays and send secret notifications to guard against physical threats or coercion attempts.

The purpose behind sharing the B-SSL concept, including its whitepaper, is to invite peer review and discussion regarding its Miniscript structure, the expressiveness of its policy, and operational safety features. Francesco encourages feedback from the community to refine and ensure the robustness of B-SSL before its practical implementation.