Cool application of isogeny crypto! I wonder if isogenies could allow us to solve the problem of efficiently detecting stealth transactions on the blockchain. This might be a great food for thought for isogeny senseis like @asanso.
The problem was originally posed by Vitalik on ethresearch here.
So far, we do not have many solutions to this problem. I will refrain from mentioning engineering-based solutions that do not really improve the asymptotic complexity of detecting stealth transactions in the
total number of stealth transactions on the blockchain, e.g., viewtags. We really want, at minimum a sublinear detection complexity, but obviously, the best would be constant work on the recipients’ end. A super dense literature review:
- Fuzzy Message Detection: a delicate tradeoff between efficiency and privacy.
- Private Signaling: strong privacy assumptions: either a TEE or two non-colluding servers are needed.
- Oblivious Message Retrieval: FHE-based solution with large detection keys. Zcash and Penumbra are going to deploy it soon.
Two really recent works:
4) Group Oblivious Message Retrieval: extends and improves on Oblivious Message Retrieval by supporting tags for groups.
5) Scalable Private Signaling: applies TEEs and Oblivious RAMs.
Can isogenies help us solve this problem? Does isogeny-based crypto allow us to build a detection scheme, where both the sender’s and recipient’s work is low, say polylogarithmic in the number of total stealth transactions on the blockchain?