In what order is the blockheader hashed?

Question

In what order are the hash of the previous block, the root of the merkle and the nonce hashed to produce the hash of the next bitcoin block?

Answer 1

They are hashed in the order they appear in the network serialisation:

block

The block message is sent in response to a getdata message which requests transaction information from a block hash.

Field Size	Description	Data type	Comments
4	version	int32_t	Block version information (note, this is signed)
32	prev_block	char[32]	The hash value of the previous block this particular block references
32	merkle_root	char[32]	The reference to a Merkle tree collection which is a hash of all transactions related to this block
4	timestamp	uint32_t	A Unix timestamp recording when this block was created (Currently limited to dates before the year 2106!)
4	bits	uint32_t	The calculated difficulty target being used for this block
4	nonce	uint32_t	The nonce used to generate this block… to allow variations of the header and compute different hashes
1+	txn_count	var_int	Number of transaction entries
?	txns	tx[]	Block transactions, in format of "tx" command

The block header is hashed. So from version to nonce inclusive.

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Related:

• What data is hashed to produce the block hash?
• What are the components of the raw block shown in this image?
• https://medium.com/hackergirl/how-to-calculate-the-hash-of-a-block-in-bitcoin-8f6aebb0dc6d