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Validator-contracts.md

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Validator Contracts

Majority List

This contract starts with an initial set of validators supporting each other. Validator can add or remove support given to as many addresses as they want. If an address is supported by more than a half of validators then it becomes a validator, similarly if support for a validator falls below a half then they are removed. Support can not be added once MAX_VALIDATORS is reached. Validators are automatically reported if they misbehave and support is removed after MAX_INACTIVITY period.

The following is the user facing ABI that can be used to interact with the contract:

[{"constant":true,"inputs":[{"name":"validator","type":"address"}],"name":"highSupport","outputs":[{"name":"","type":"bool"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"validatorsList","outputs":[{"name":"","type":"address"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"validator","type":"address"}],"name":"removeValidator","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"validator","type":"address"}],"name":"addValidator","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"validator","type":"address"}],"name":"getRepeatedBenign","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"validator","type":"address"}],"name":"getSupported","outputs":[{"name":"","type":"address[]"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"MAX_VALIDATORS","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"getValidators","outputs":[{"name":"","type":"address[]"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"reporter","type":"address"},{"name":"validator","type":"address"}],"name":"firstBenignReported","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":true,"inputs":[{"name":"validator","type":"address"}],"name":"getSupport","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"validator","type":"address"}],"name":"addSupport","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"validator","type":"address"}],"name":"absolveFirstBenign","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"MAX_INACTIVITY","outputs":[{"name":"","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"validator","type":"address"},{"name":"blockNumber","type":"uint256"}],"name":"reportBenign","outputs":[],"payable":false,"type":"function"},{"inputs":[],"payable":false,"type":"constructor"},{"payable":true,"type":"fallback"},{"anonymous":false,"inputs":[{"indexed":true,"name":"parent_hash","type":"bytes32"},{"indexed":true,"name":"nonce","type":"uint256"},{"indexed":false,"name":"new_set","type":"address[]"}],"name":"ValidatorsChanged","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"reporter","type":"address"},{"indexed":true,"name":"reported","type":"address"},{"indexed":true,"name":"malicious","type":"bool"}],"name":"Report","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"name":"supporter","type":"address"},{"indexed":true,"name":"supported","type":"address"},{"indexed":true,"name":"added","type":"bool"}],"name":"Support","type":"event"}]

Inspecting the state

  • getValidators method lists the current validators
  • getSupport returns the number of validators what support a given validator
  • getSupported lists all addresses supported by the given validator

Adding support

To support an address to become a validator execute the addSupport with that address.

Removing support

Removing support should be done by executing reportBenign twice, second time being after MAX_INACTIVITY seconds.

Absolving a validator

After executing reportBenign a validator may change their mind. They should then execute absolveFirstBenign to forget about it.

Inactivity

If a validator misses a block nodes will automatically execute reportBenign, thus if inactivity exceeds or repeats after MAX_INACTIVITY period, support will be removed.

Malicious behaviour

If a validator runs two signing nodes or modifies the code to attempt to create forks other nodes will automatically remove support for them.