The core security proposition of Plasma revolves around honest users being able to exit the child chain (in other words, withdraw funds to the root chain) at any time. To exit the child chain, a user submits an exit transaction – along with an exit bond – to the root chain. The exit is subject to a challenge period, during which any user can prove, if applicable, that the exit is invalid. If successfully shown to be invalid, the exit is not processed, and the challenger is awarded the exit bond. This exit game is entirely dependent on the root chain.