I have a question for @ebfull specifically but figured I’d ask in a thread rather than DM in case the answer is useful to the rest of the community.
In the Halo 2 explainer post, it says:
Recursive proof composition allows a single proof to attest to the correctness of practically unlimited other proofs, effectively allowing a large amount of computation (and information) to be compressed. This is an essential component for scalable Zcash, not least because it allows us to horizontally scale the network while still allowing pockets of participants to trust the integrity of the remainder of the network.
Emphasis mine.
Regarding the bold section in the quote above, I’m wondering if this is describing a sidechains approach that is at all similar to that implemented by Zendoo? From the Zendoo whitepaper abstract:
In this paper, we introduce Zendoo, a construction for Bitcoin-like blockchain systems that allows the creation and communication with sidechains of different types without knowing their internal structure. We consider a parent-child relationship between the mainchain and sidechains, where sidechain nodes directly observe the mainchain while mainchain nodes only observe cryptographically authenticated certificates from sidechain maintainers. We use zk-SNARKs to construct a universal verifiable transfer mechanism that is used by sidechains.
Moreover, we propose a specific sidechain construction, named Latus, that can be built on top of this infrastructure, and realizes a decentralized verifiable blockchain system for payments. We leverage the use of recursive composition of zk-SNARKs to generate succinct proofs of sidechain state progression that are used to generate certificates’ validity proofs. This allows the mainchain to efficiently verify all operations performed in the sidechain without knowing any details about those operations.
In any case, I am quite interested in learning more about the “horizontal scaling” technique described in the Halo 2 post!
Edit: oops tagged wrong Sean 
