App

We discussed the basic blocks needed for creating a channel in the payment channel example. Additional fields in the channel parameters and state are required to define the app logic and state: An app field in the parameters stores the address of an on-chain app contract and a data field in the state is used to insert arbitrary data for describing app states.

We will implement two components in this section:

1. An on-chain contract implementing Perun’s Ethereum App interface. Most notably, the interface requires a validTransition function to validate the transition between app states to make the app logic enforceable without full consensus.

2. An off-chain app implementing Perun’s Core App interface. It mirrors the on-chain validTransition function for sanity checks and implements app data encoding.

Note

The contract will act as an on-chain reference to validate the game’s state transitions. This procedure is only needed in case of disputes. The primary point of interaction is still the off-chain app channel.