Skip to main content


header is a sub-structure of Block and UncleBlock, including raw and nonce.

Structure of header

Fields & Description

rawRawHeaderThe payload of the block header. For more, see RawHeader.
nonceuint128The solution of the PoW puzzle. Similar to Bitcoin nonce.

Verification Process for Header

This following snippet describes the process to validate the PoW for a block header in the Nervos CKB blockchain:

  1. Serializing and hashing the block's raw data.
  2. Concatenating the hash with the nonce.
  3. Running the concatenated result through the Eaglesong algorithm.
  4. (Optional) Re-hashing for the Testnet.
  5. Converting the final output to an integer and ensuring it meets the required difficulty target.
pow_hash := ckbhash(molecule_serialize(raw))
pow_message := pow_hash || to_le(nounce)
pow_output := eaglesong(pow_message)
// for Testnet, there is another round of hash
// pow_output = ckbhash(pow_output)

from_be(pow_output) <= compact_to_target(raw.compact_target)

Functions used in the pseudocode

  • :=: assignment
  • ||: binary concatenation
  • ckbhash: Blake2b hash with CKB specific configuration
  • to_le: converts unsigned integer to bytes in little-endian. The bytes count is the same with the integer width.
  • from_be: converts bytes encoded in big-endian to an unsigned integer
  • molecule_serialize: serializes a structure into binary using its schema
  • eaglesong: CKB’s Proof-of-Work consensus algorithm. See RFC0010: Eaglesong
  • compact_to_target: restores the target from its compact form, which is the difficulty target encoded by raw.compact_target

Header Hash Derivation & Usage

The header is hashed to produce a unique header_hash. This header_hash is then used to reference the block.

header_hash := ckb_hash(molecule_serialize(header))