Update Protocol
Last updated
Last updated
Once an application has been installed into the state channel, the multisignature wallet has transferred control over the installed amount from the free balance to the application's resolve
function, a mapping from application state to funds distribution. For example, in the case of Tic-Tac-Toe, a possible payout function is: if X wins, Alice gets 2 ETH, else if O wins Bob gets 2 ETH, else send 1 ETH to Alice and Bob.
As the underlying state of the application changes, the result of the payout function changes. It is the job of the Update Protocol to mutate this state, independently of the rest of the counterfactual structure.
Using our Tic-Tac-Toe example, if Alice decides to place an X on the board, Alice would run the Update Protocol, transitioning our state to what is represented by the figure above. Notice how both the board changes and the local nonce for the app is bumped from 0 to 1. To play out the game, we can continuously run the update protocol, making one move at a time.
For the below messages, the digest that is signed is represented as the following:
Type: UpdateParams
SetState
MessageTODO: Add a field for the encoded action
SetStateAck
MessageCommitment for SetState
and SetStateAck
:
The commitment can be visually represented like:
This transaction invoke the setState
function with the signatures exchanged during the protocol.
Field
Type
Description
appInstanceId
bytes32
Hashed App Identity
newState
AppState / JSON-like
New state to set to
Field
Description
protocol
"update"
params
An UpdateParams
object
fromAddress
The address of Alice
toAddress
The address of Bob
seq
1
signature
Alice's signed commitment digest
Field
Description
protocol
"update"
fromAddress
The address of Alice
toAddress
The address of Bob
seq
2
signature
Bob's signed commitment digest