Skip to main content

Data loading

⚠️ This step will be executed by Horizen admins and does not require actions for ZEN holders

The scope of this step is to load the balances obtained in the previous dump step into the vault smart contracts used for the migration.
This operation is performed by firing a batch of transactions, only by an authorized Horizen admin (its address is whitelisted in the vault contracts).

Detailed instructions are in the README.md file of the horizen-migration Git repository, together with the scripts to be executed (they use the Hardhat framework).

Migration data cumulative hash​

The concept of "cumulative hash" is used as a "fingerprint" of the dump data.
Assuming we have a list of dump tuples composed by [address,balance], ordered by address, we define it with the following pseudo-code rule:

cumulative_hash = "0x0000000000000000000000000000000000000000000000000000000000000000"
for each dump tuple:
    overall_hash = keccak-256-hash(overall_hash, tuple.address, tuple.value)

In the data loading process, it is:

  • first calculated off-chain
  • fed into the smart contract
  • Inside the solidity code:
    • recalculated during the batch data loading
    • compared with the initial one, to check the correctness of the loading and to receive confirmation that the loading has been completed (claiming methods will be enabled only at this point)

Furthermore, in the migration check step, the same hash can be recomputed off-chain by any third-party, and compared with the one stored in the smart contract.