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What if a miner just broadcasts the header and never broadcasts the body?
For example: A miner, after having successfully mined some block, just broadcasts the header for all other miners and hide the body or never give the information of the body. Under this situation, what will happen? Will all other miners just start the mining based on that header?
Since nobody can determine that the block is valid, they will treat it just like anything else that they cannot determine is valid -- they will ignore it.
Miners can't start mining based on the header because without the body, they do not know the valid UTXO set. I guess they could, but they couldn't put any transactions in the block except for a transaction to reward themselves. But they still won't. What if the block body is later revealed and it's invalid? They could be wasting time trying to mine blocks for an invalid chain.
Full nodes will want to see the body in order to maintain their UTXO set.
The miners block headers alone are not enough.
Also, the miner would never be able to spend the block rewards, because that depends on the UTXO state.
