  In this paper, we present Zecale, a general purpose SNARK proof aggregator
that uses recursive composition of SNARKs. We start by introducing the notion
of recursive composition of SNARKs, before introducing Zecale as a privacy
preserving scalability solution. Then, we list application types that can
emerge and be built with Zecale. Finally, we argue that such scalability
solutions for privacy preserving state transitions are paramount to emulate
"cash" on blockchain systems.
