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