does the block gets signed by all authorities in aura?

Question

I have read their official documentation and I'm not sure I completely understand the process of block creation or finalization.

I know that after each period of time, there is a block author that creates a block and broadcast it to the other validators, does the others need to sign the block and resend it and only after 2/3 collected signatures the block gets added? or they simply accept it based on the BlockImport rules?

In other words is it like proof of work where when you receive a block you need to verify its validaity based on some rules and you don't care whether others added it or not, or is it that you need another round to make sure everyone received the same block from the author and then add it?

Answer 1

The 2/3 number actually comes from another mechanism, grandpa, which achieves finality. The logic of block authoring and block finalization is split between aura and grandpa. The aura authorities take turns producing blocks, and each authority indeed seals the block. Then the grandpa authorities take votes on the correct block and that's where the 2/3 threshold appears.

This talk by Bill Laboon about hybrid consensus (one that uses a finality gadget) is very helpful, although it talks about BABE rather then AuRa (another block production mechanism).