Hyperledger Burrow is a re-implementation of the Ethereum Virtual Machine (EVM) and blockchain technology, but with a few key changes. First, instead of using the proof-of-work consensus algorithm used by the public Ethereum chain, Burrow is designed around the Tendermint consensus algorithm (See Chapter 7, Achieving Consensus). This means there are no miners and no mining to be done on Burrow-based projects.

Second, Hyperledger Burrow is permissioned—the computers allowed to participate in a Hyperledger Burrow network are known and granted access, and the computers signing blocks (called validators, as in Tendermint) are all known. This is very different than Ethereum, where anyone can anonymously download the Ethereum software and join the network.

Smart contracts written for the EVM will still mostly work. Due to the change in consensus, there are also changes in the way Gas is used. In the public Ethereum blockchain, each transaction costs Gas, depending on the complexity of the transaction, and each block has a Gas limit. Depending on the network load, participants have to pay a variable cost in Ether for the Gas needed for their transactions. In Burrow, these complexities are mostly dispensed with. Each transaction is gifted a basic amount of Gas automatically. Because the Gas is still limited, Burrow is able to guarantee that all transactions eventually complete—either by succeeding or failing—because they run out of Gas.

For more on the EVM, solidity language, and other aspects of Ethereum shared with Hyperledger Burrow, please see Chapter 12, Ethereum 101.