I am using Alethio block explorer in an IBFT2 based chain. I am trying to understand some fields there.

Does anyone know what they mean?

  • Are the COMMITSEALS the signature of the validators?
  • What is MIX HASH?
  • What is LOGS BLOOM? Are the logs of the blocks? Is it a kind of processing using a bloom filter?
  • I also do not understand what SHA3UNCLES. It also appears on EtherScan with the following description: "The mechanism which Ethereum Javascript RLP encodes an empty string". I know RLP but I still could not understand why this info is relevant to be presented in a block explorer.

Thank you

1 Answer 1


Here is a description to some of the changes to the Ethereum's block header for IBFT. In particular:

  • mixHash: Fixed magic number 0x63746963616c2062797a616e74696e65206661756c7420746f6c6572616e6365 for Istanbul block identification.
  • ommersHash (SHA3_UNCLES): Must be UNCLE_HASH as uncles are meaningless outside of PoW. UNCLE_HASH is a constant defined as Keccak256(RLP([])) as uncles are meaningless outside of PoW.
  • CommittedSeal: The list of commitment signature seals as consensus proof.

LogsBloom isn't mentioned so it should have the same purpose than in Ethereum. It is a bloom filter constructed from the events to facilitate search.

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