Hi guys, I have been working on a new tx protocol called Seraphis. An outline is here: gist.github.com/UkoeHB/24f6be6125684046c5c4d9f49351bccf. I am planning to write a preprint for it, but that is weeks or months away from now.

With a Groth/Bootle (Grootle) ring signature for membership proof, this would look similar to Triptych/etc in terms of size/verification costs. The main functional difference is how key images (linking tags) are constructed.

Grootle one-of-many proof*

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The Seraphis key images are Grootle-friendly (fixed base point), multisig-friendly (linear on private spend key), and allow full balance recovery with the private view key (inversion component based on private view key).

The essential difference compared to previous tx protocols is membership proofs sign a commitment to zero on the output address, instead of proving knowledge of the private key and constructing key images directly.