On March 9, during the Ethereum Community Conference, Vitalik Burenin, co-founder of Ethereum presented scaling solution called Plasma Cash, an even “more scalable” version of an existing solution called Plasma.
"In Traditional Plasma you can still make quadratic scaling but it cannot go exponential" Vitalik said. The main challenge is that every user must download and authenticate each Plasma block which appears to be very expensive.
The solution: Plasma Cash only require users to pay attention to the blocks that contain coins they want to keep track of.
Using the ERC721 is going to give serial number to particular tokens at different denomination. This is where the "cash" part comes in. In other words the only thing the user have to check is data availability.
How Plasma Cash works?
• Each deposit creates a "coin" with a unique ID
• Coins cannot be split or merged
• A transaction spending must be included in the position in the Merkle tree corresponding to the coin ID
Basically no one can take another user’s coin without the owner of the coin being alerted. This is a good news for the users because they can run their money through the Plasma exit procedure and get their money out even and exchange gets hacked.
You can watch Vitalik's entire presentation here: