Table 2.

Solution to attack methods in PoW and PoA.

Attack	PoW	PoA
Malicious contributor	Malicious miner needs 51% of hashing power for successful attach	Any signer may only mint 1 block out of every K. Damage is limited. Signer can be voted out.
Censoring contributor	Miner censoring blocks is penalized and their blocks are rarely included in the chain	Signers censoring blocks with negative votes are limited to 1 block out of N/2 block.
Spamming contributor	Spamming transactions requires money to be spent on transaction fees	Signers injecting new vote proposals inside every block they mint is mitigated by placing a limit on the vote window.
Concurrent contributors	Concurrent block discovery is rare. In this case best fork is selected for chain continuation.	As at any point in time N-K + 1 miners are allowed to mint. To avoid racing we add a small random “offset” to the time it releases a new block.