Truebit Contracts

Truebit seeks to extend the class of computations that can, with high probability, be performed 'correctly' in a decentralized network of financially rational processors.

This working sketch follows section 4 of the whitepaper in an implementation of the Incentive layer contracts.

Implementation

There are many ways in which this can be implemented; this first draft assumes a library-driven structure, consisting of three core structs: Jackpot, Task, and TaskBook.

Jackpot

To incentivize verifiers, a progressive jackpot is established prior to the negotiation of Tasks. The idea here is to collect a verification tax as a fixed multiple of a Task's difficulty, awarding a fixed fraction of its holdings when a 'forced error' is in effect.

In order to facilitate multiple methods of payment, the rules and operation of the Jackpot are defined here in terms of arbitrary quantities of type uint256. The intention here is to enable the construction of Jackpots, and subsequently Tasks, whose payment structure is defined in separate contracts.

Properties

Type	Name	Description
address	addr	Address of the Jackpot repository.
uint	tax	Universal Tax rate to be applied for this jackpot.
uint	fe_rate	Forced error rate, determining the frequency of payouts.
bool	active	Set when this Jackpot is initialized in a contract.

Methods

init(uint tax, uint fe_rate)

deposit (uint amount)

Events

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Task

The main item encapsulating the properties, operations, and events appearing across the lifecycle of a Task.

Thought - Perhaps the numerous uint's can be collected into a list of 'critical block times'.

Properties

Type	Name	Description
State	state	The current state of this Task.
Jackpot	jackpot	Jackpot repository with which this Task is associated. This is important for when Jackpot actions are triggered.
address	giver	The address responsible for the creation of this Task.
address	solver	The address elected to solve this Task.
uint	reward	The reward offered for correct solution of this Task. The method of payment is to be determined by the importing contract.
uint	min_deposit	The minimum deposit required from a solver of this Task.
uint	created	The block number at which this Task was created.
uint	elected	The block number at which a solver is first elected.
uint	commited	The block number at which a solver submit his solution hashes.
uint	challenged	The block number at which a challenge is initiated.
uint	timeout	The timeout period between state transitions. Failure to comply with the protocol in a timely manner results in deposits forfeited to the Jackpot.
bytes32	init	Keccak-256 hash of the initial VM state, supplied by Giver.
bytes32[2]	solution_hashes	Keccak-256 hashes of correct and incorrect terminal VM states, supplied by Solver.
bytes32	rand_hash	Keccak-256 hash of the solver's random bits r.
bytes32	solution	Keccak-256 hash.
bool	solution_choice	Choice of one of the two above solution hashes, provided by the Solver upon revelation of the block hash following the submission of solution_hashes.
mapping (address => uint)	deposits	Deposit amounts supplied by solver and verifiers.

Methods

init()

bid()

commit()

reveal()

challenge()

Events

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TaskBook

A TaskBook simply collects Tasks together in order to expose a unified interface for prospective solvers and verifiers.