This PR integrates the hashchain feature into the Aurora Engine contract (see https://github.com/aurora-is-near/AIPs/pull/8). This change is fully backwards compatible because by default there is no hashchain present in the contract state and therefore no hashchain computation is done.
The method to activate the hashchain is start_hashchain requires the contract to be paused and can only be called by a privileged account (I chose to use the key manager instead of introducing a new role). These restrictions are necessary because the hashchain is initialized with a value based on the Engine's transaction history (to enable validating Aurora blocks starting from the deployment of the contract).
Performance / NEAR gas cost considerations
After activating the hashchain there will be a small increase in gas usage because of the hashchain computation. It's not very much for most transactions (as seen in the performance regression tests), but the amount of gas is proportional to the size of the input + output of the transaction (because we compute a hash from this data).
Testing
The tests have been changed to enable the hashchain by default. Therefore all existing tests are running the hashchain code and testing that the Wasm and Standalone results match (this is important because the Refiner will be computing hashchain values off-chain using the Standalone Engine). An additional test has been added for the hashchain feature itself.
Additional information
Note: the diff in contract_methods is relatively large, but the code changes are minimal. All that happened is the existing function bodies were wrapped in with_hashchain, which changed the indentation. Viewing the PR with whitespace changes ignored may make this section easier to review.
Description
This PR integrates the hashchain feature into the Aurora Engine contract (see https://github.com/aurora-is-near/AIPs/pull/8). This change is fully backwards compatible because by default there is no hashchain present in the contract state and therefore no hashchain computation is done.
The method to activate the hashchain is
start_hashchainrequires the contract to be paused and can only be called by a privileged account (I chose to use the key manager instead of introducing a new role). These restrictions are necessary because the hashchain is initialized with a value based on the Engine's transaction history (to enable validating Aurora blocks starting from the deployment of the contract).Performance / NEAR gas cost considerations
After activating the hashchain there will be a small increase in gas usage because of the hashchain computation. It's not very much for most transactions (as seen in the performance regression tests), but the amount of gas is proportional to the size of the input + output of the transaction (because we compute a hash from this data).
Testing
The tests have been changed to enable the hashchain by default. Therefore all existing tests are running the hashchain code and testing that the Wasm and Standalone results match (this is important because the Refiner will be computing hashchain values off-chain using the Standalone Engine). An additional test has been added for the hashchain feature itself.
Additional information
Note: the diff in
contract_methodsis relatively large, but the code changes are minimal. All that happened is the existing function bodies were wrapped inwith_hashchain, which changed the indentation. Viewing the PR with whitespace changes ignored may make this section easier to review.