Creating native coins by native-to-native bridge using RewardByBlock contract

[varasev]

Title

  Title: Creating native coins by native-to-native bridge using RewardByBlock contract
  Layer: Bridges

Abstract

When the bridge needs to generate native coins on POA Network side, it will be able to use RewardByBlock (BlockReward) smart contract, the support of which was added in Parity 1.11: openethereum/parity-ethereum#8419.

RewardByBlock contract allows pointing Parity at how many coins must be generated after creating of each block and on which addresses these coins must be accrued.

Rationale

It is the easiest and possibly only way native coins can be generated for the bridge.

Implementation

We need to complement RewardByBlock by the possibility of accruing coins to the specified address(es).

Smart contract of the bridge has to call some function of RewardByBlock, which will write the specified addresses and appropriate amounts of coins into contract's state. When a new block is being generated, and reward function is being called, those addresses and amounts will have to be in return statement of reward function and will have to be removed from contract's state.

RewardByBlock contract must control the address (msg.sender) of the bridge's contract.

[varasev]

Prototype: https://gist.github.com/rstormsf/9d1d6386885ba9cc3ae8821060b11014

[varasev]

Small test: https://gist.github.com/rstormsf/16f6abab066d3c28215fb3ca8cab1363

[varasev]

RewardByBlock contract was supplemented by addExtraReceiver function in poanetwork/poa-network-consensus-contracts#144.

Unit tests were also added: https://github.com/poanetwork/poa-network-consensus-contracts/blob/35a618d1ebb60db60c6fd006f8a153be695c2cef/test/reward_by_block_test.js

That function may only be called once for the same receiver until a new block is created (reward function is called).

addExtraReceiver may only be called by bridge contract which address is stored in the bridgeContract constant: https://github.com/poanetwork/poa-network-consensus-contracts/blob/35a618d1ebb60db60c6fd006f8a153be695c2cef/contracts/RewardByBlock.sol#L23

[varasev]

https://github.com/varasev/test-block-reward repo has been updated to be able to rebuild contracts with npm run build.

Now if some contract code changes, we can recompile contracts with npm run build and completely restart setup with npm run restart.

I'm going to update contracts in that setup to the current versions available in https://github.com/poanetwork/poa-network-consensus-contracts/tree/35a618d1ebb60db60c6fd006f8a153be695c2cef and make send.js demo script showing how RewardByBlock.addExtraReceiver function works.

[varasev]

https://github.com/varasev/test-block-reward has been updated with the latest versions of smart contracts and complemented with npm run accrue 1 command that allows accruing one coin to a test address. Instructions are in README.