Parent Blockchain โ๏ธ: We assume the existence of a parent-ledger, an integrity protected and immutable root of trust (e.g. a blockchain), that allows for the convenient deployment of tamper-proof smart contracts and which acts as timestamping service. The ledger contains a global view of accounts, their balances and transactions, and extra associated data. Each account in the ledger is controlled by a private key, which authorizes transactions from the account.