  Plasma is a framework for scalable off-chain computation. We describe and
evaluate Plasma Cash, an improved Plasma construction which leverages
non-fungible tokens and Sparse Merkle Trees to reduce the data storage and
bandwidth requirements for users. We analyze the cryptoeconomic exit and
challenge mechanisms used to keep user funds secured, even when the Plasma Cash
chain's consensus algorithm is compromised. A reference implementation is
provided for evaluation. Finally, we briefly discuss further improvements that
can be made to the Plasma Cash protocol such as arbitrary denomination
payments, less user data checking, fast and optimistic exits.
