How does mixHash be used in qbft consensus?

[kth-tw]

I tried to use quorum-genesis-tool build a quorum network. The genesis.json include a value mixHash, ant it is always set to 0x63746963616c2062797a616e74696e65206661756c7420746f6c6572616e6365 in here
If I choose qbft as consensus, what does this value mean to?

[baptiste-b-pegasys]

Hello, from our code, this value is the istanbul digest.

	// IstanbulDigest represents a hash of "Istanbul practical byzantine fault tolerance"
	// to identify whether the block is from Istanbul consensus engine
	IstanbulDigest = common.HexToHash("0x63746963616c2062797a616e74696e65206661756c7420746f6c6572616e6365")

In ethereum, mixHash is used for the mining PoW consensus (https://gist.github.com/0mkara/b953cc2585b18ee098cd#file-genesis-md), for our PoA, it's for identifying the consensus engine, that's the same function.

You may try a different value and see if it is possible to change it as you want to.

[kth-tw]

I guess mixHash is used here

If I am interested in this part(genesis file, istanbul digest, ...etc) , is there a document to refer to?

[baptiste-b-pegasys]

Ok therefore it's not possible to change the mixHash for istanbul consensus.
I found ethereum/EIPs#650 (mixHash: Fixed magic number 0x63746963616c2062797a616e74696e65206661756c7420746f6c6572616e6365 for Istanbul block identification.)

#1084

[kth-tw]

Thank you for your help finding reference. It seems I had a big misunderstood. This is the parameter of geth, not added by quorum.