Is there any constrain forced on Parachains for block authoring logic?

Question

I am reading Cumulus PDK and Parachain documentations, and looking forward to converting our project to a parachain and join the Polkadot ecosystem.

However, I am confused regarding the parachain consensus mentioned in the documents. In FAQ section of parachains it is specified that "Parachains cannot use other consensus algorithms that provide their own finality", I am assuming it's about GRANDPA and not Aura or BABE. Refer to Parachains FAQ

Since Aura/ BABE are only block authoring side of the consensus, according to the FAQ mention above it should not impact the development of parachain even if I have a different block authoring logic.

Now, The document from Cumulus PDK, which specifies that the "Parachain will be able to use Aura, BABE, etc. (Not supported at the moment)". The focus is on the text in bold "Not supported at the moment". So according to Cumulus document I wont be able to use other block authoring consensus for the parachain node.

So if I want to join polkadot parachain ecosystem, can I use any consensus for authoring blocks as long as the finality is using the GRANDPA or is it not supported yet as mentioned in the Cumulus document.

Thank you,

Answer 1

Polkadot Consensus is known as hybrid consensus. Unlike other protocols, Hybrid consensus splits up the finality gadget from the block production mechanism.

As for block production, this happens both on the relay chain and the parachains' side. For a parachain it is possible to use AURA or BABE (or any other custom block production logic) to determine who is allowed to produce a block and send the PoVblock to the assigned validators. This probably isn't as easy as it sounds though.

Regarding finality, this is solely determined on the relay chain (Polkadot's shared security). Thus, a parachain doesn't have to and shouldn't implement its own finality.