go-ethereum/docs/xdc/validator.md

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The `XDCValidator.sol` contract helps with decentralized identity checks (called KYC) and managing validators. It does these tasks: handles user identity verification, lets users suggest and choose validators, and allows the community to vote on whether to accept identity checks that might not pass the standards.
## Become a masternode
The process of becoming a masternode is shown in the diagram below:
```text
User
O
/|\
/ \
|
| Upload KYC information to participate
| in the candidate process.
v
+-----------------+
| uploadKYC() |
+-----------------+
|
| Become an owner by depositing XDC
| (minCandidateCap) and proposing
| a candidate address.
v
+-----------------+
| propose() | Propose an address as a candidate
+-----------------+
|
|
v
Now you are a candidate node owner
```
## Kick out the masternodes
An invalid KYC will cause a owner to lose all of his candidate node. The process is shown in the diagram below:
```
+-----------------+
| Candidates |
| (Node) |
+-----------------+
|
|
|
v
+-----------------+
| voteInvalidKYC()| Report invalid KYC for other candidates
+-----------------+
|
| Check the invalid vote percentage
| using `invalidPercent()`
|
v
+---------+---------+
| |
v v
75% against (else)
invalid KYC valid KYC
the owner of KYC Candidate remains valid.
Lost his candidates
and funds
```
## Resign
If you want to resign from candidacy. The process is shown in the diagram below:
```text
Owner
O
/|\
/ \
|
|
v
+----------+
| resign() |
+----------+
| Withdraws candidacy
|
|
| Locking Period
| 30 days lock-up
|
|
v
+------------+
| withdraw() |
+------------+
Withdraw funds from contract
```
## Functions
Implementing KYC management and Validator management through several functions, with specific roles as follows:
### uploadKYC
Uploads user KYC. This operation only stores the user's verification details and does not confer owner status.
Function Signature:
```solidity
function uploadKYC(string memory kychash)
```
Who can use: Anyone(msg.sender)
Modifers: none
Parameters:
- `kychash` : The hash of the user's KYC information.
### propose
Owner proposes `_candidate` to become a masternode.
Function Signature:
```solidity
function propose(address _candidate)
```
Who can use: Anyone who has uploaded KYC (or is the owner) and has paid enough deposit.
Modifers: `onlyKYCWhitelisted`, `onlyValidCandidateCap`,`onlyNotCandidate`
Parameters:
- `_candidate` : The address of the nominee.
### vote
Deposits an amount not less than minVoterCap into the contract to cast a vote for the candidate.During voting, the candidate's total cap value will be updated.If it's the first time voting:
- The voter will be added to the candidate's voter list.
- The voter's stake for that candidate will be updated.
Function Signature:
```solidity
function vote(address _candidate)
```
Who can use: Anyone (msg.sender) who has paid enough voting amount
Modifers: `onlyValidVoterCap`,`onlyValidCandidate`
Parameters:
- `_candidate` : The address of the candidate receiving the vote.
### unvote
Revokes a vote for a candidate, with the corresponding funds refunded after X blocks.
Function Signature:
```solidity
function unvote(
address _candidate,
uint256 _cap
)
```
Who can use: Anyone (msg.sender) who has a valid vote for a specific candidate node
Modifers: `onlyValidVote`
Parameters:
- `_candidate` : The address of the candidate for whom the vote is to be revoked.
- `_cap` : The amount to be refunded.
### voteInvalidKYC
Allows the masternode, through a vote among masternode owner , to decide if another owner's KYC information meets the requirements. If over 75% of the owners deem it invalid, the KYC is considered Unqualified, leading to the forfeiture of funds from that owner and all their candidates.
Function Signature:
```solidity
function voteInvalidKYC(address _invalidCandidate)
```
Who can use: Candidate
Modifers: `onlyValidCandidate`,`onlyValidCandidate`
Parameters:
- `_invalidCandidate` : The address of the candidate whose owner's KYC validity is under judgment.
### invalidPercent
Checks the percentage of "Invalid KYC" votes for a particular owner, indicating the level of community approval regarding that owner's KYC information.
Function Signature:
```solidity
function invalidPercent(address _invalidCandidate) returns (uint)
```
Who can use: Anyone(msg.sender)
Modifers: `onlyValidCandidate`
Parameters:
- `_invalidCandidate` : The address of the candidate whose owner's KYC recognition level needs to be queried.
The user can withdraw from candidacy and reclaim their funds upon meeting certain conditions.
### resign
Withdraws candidacy, with the corresponding deposit refunded after X blocks. This function can only be called by the owner.
Function Signature:
```solidity
function resign(address _candidate)
```
Who can use: Owner
Modifers: `onlyOwner`,`onlyCandidate`
Parameters:
- `_candidate` : The address of the candidate wishing to withdraw their candidacy.
### withdraw
This function allows for the withdrawal of funds from the contract, exclusively available to approved candidates.
Function Signature:
```solidity
function withdraw(uint256 _blockNumber, uint _index)
```
Who can use: Addresses that have previously staked (as owner or voter) and have unlocked funds
Modifers: `onlyValidWithdraw`
Parameters:
- `_blockNumber` : The block height associated with the withdrawal request. This is used to link the withdrawal action to a specific point in the blockchain's history.
- `_index` : An index pointing to the user's current withdrawal request in the record. This helps in locating and processing the correct withdrawal operation for the candidate.
## Modifers
The contract incorporates several Modifiers to govern the execution conditions of functions, serving specific purposes as outlined below:
- **onlyValidCandidateCap**: The deposited amount (`msg.value`) must exceed `minCandidateCap`.
- **onlyValidVoterCap**: The amount deposited into the contract (`msg.value`) must be greater than `minVoteCap`.
- **onlyKYCWhitelisted**: A KYC record is required, or the address must have proposed or owns another candidate.
- **onlyOwner(address _candidate)**: restricts calls to the owner associated with the specified candidate.
- **onlyCandidate(address _candidate)**: allows calls only from the candidate specified.
- **onlyValidCandidate(address _candidate)**: permits calls exclusively from a legitimate candidate.
- **onlyNotCandidate(address _candidate)**: permits calls only from addresses that are not candidates.
- **onlyValidVote(address _candidate, uint256 _cap)**: requires the vote to be legitimate with respect to the candidate and the cap.
- **onlyValidWithdraw(uint256 _blockNumber, uint _index)**: demands that the block number is reasonable and valid for the withdrawal operation.