Proof of Authority

AuthorityRound (AuRa)

Aura is one of the Blockchain consensus algorithms available in OpenEthereum (previously Parity). It is capable of tolerating up to 50% of malicious nodes with chain reorganizations possible up to a limited depth, dependent on the number of validators, after which finality is guaranteed. This consensus requires a set of validators to be specified, which determines the list of blockchain addresses which participate in the consensus at each height. Sealing a block is the act of collecting transactions and attaching a header to produce a block.

At each step the primary node is chosen that is entitled to seal and broadcast a block, specifically step modulo #_of_validatorsthe validator is chosen from the set. Blocks should be always sealed on top of the latest known block in the canonical chain. The block's header includes the step and the primary's signature of the block hash.

Block can be verified by checking that the signature belongs to the correct primary for the given step. Finality of the chain can be achieved within at most 2 x #_of_validator steps, after more than 50% of the nodes are signed on a chain and then they are signed again on those signatures.

History of POA

On March 6, 2017, a group of blockchain companies announced new blockchain based on Ethereum protocol with Proof of Authority consensus . Spam attack on the Ropsten testnet was the reason to create a new public test network. This network was named Kovan, for a metro station in Singapore, where companies who founded the network are located. It is a common name convention for Ethereum test networks, for example, Morden, Ropsten, and Rinkeby are names of metro stations.

Adoption of Kovan blockchain

In the table below we show stats for Main (Homestead) and Test (Kovan) Ethereum networks.

Network	Type	Blocks mined	Tx created	Contract created	Accounts created
Kovan	Testnet	3,417,527	2,859,549	54,384	18,082	Text
Homestead	Mainnet	4,203,319	50,374,359	1,488,072	4,957,479	Text

Large numbers of transactions, smart contracts, and accounts on the test network show adoption from the community and proven utility benefit.