The cat's out of the bag with the newest episode of TFTC - announcing here first on Nostr:

Sigbash v2 is live! We've switched to a new approach that I've decided to call Oblivious Signing: thanks to the power of MuSig2, WebAssembly, and zero knowledge proofs, our signer never sees your signing key *or* the transactions you want us to sign.

instead, when you register a key, first you commit to a signing policy (anything - input and output amounts, destination addresses, time windows allowed for signing, you name it) - and we'll only sign transactions that match your policy.

Policies are as complex as you need and as private as we could possibly make them. Our beta is live on signet now at https://www.sigbash.com!