arbedout first posted about Sigbash back in 2024 (#481416), but he's made a lot of progress since then.

Now he's released to signet a new version of sigbash that feels a lot more polished.

Sigbash is a cosigning service where you give Sigbash one of the keys in your multisig and they promise to sign when you ask them to. You can read about the tradeoffs of v1 here: #1196802

Sigbash v2 looks like an improvement on this.

From their FAQ:

Sigbash is a cryptographic co-signing service for Bitcoin that enables policy-based spending controls that keep transaction and policy details private.

You define spending policies (approval workflows, vendor whitelists, rate limits, etc.), and we cryptographically verify policy satisfaction while remaining blind to transaction amounts, recipients, or policy details. Institutional-grade policy enforcement meets self-custody privacy.

They've done a cool job with how they present the templates:

Or you can use their chat agent to help you draft the policy:

I think the idea is that you can specify certain spending conditions you want the key you give sigbash to enforce and it will only sign if those conditions are met. So it's not necessarily a failsafe kind of situation so much as a way of enacting a spending policy. You would still want to have a fallback spending path in case sigbash is offline or turns malicious.

I'm definitely not ready to start using something like this, but as these things get built out, they're starting to look more and more attractive to me.