← GlossaryMining
What Is Auxiliary Proof of Work (AuxPoW)? How Merge Mining Is Verified
Auxiliary proof of work (AuxPoW) is the mechanism that lets a blockchain accept a parent chain's proof of work as its own, by checking a commitment to the auxiliary block inside the parent block.
Key takeaways
- The auxiliary chain accepts proof of work performed on a different, parent chain.
- The parent block commits to the auxiliary block, so one hash effort can count for both.
- Each merge-mined chain has its own chain ID so commitments cannot be reused across chains.
- Dogecoin's code defines a merged-mining marker and a chain ID of 98 (0x0062).
What it solves
A new proof-of-work chain is easy to attack because it has little hashing power. Auxiliary proof of work lets such a chain borrow security from a larger one. Miners of the parent chain can also mine the auxiliary chain without extra hashing, and the auxiliary chain accepts that work as valid for its own blocks.
How a block is verified
A merge-mined block carries an AuxPoW structure instead of a plain nonce solution. It contains the parent block's header and the parent's coinbase transaction, plus merkle branches linking them. The coinbase includes a commitment to the auxiliary chain's block, so the proof says: this parent header meets the auxiliary chain's target, and its coinbase commits to this auxiliary block. A verifier checks the links and the work, and does not need to trust anyone.
The marker and the chain ID
To find the commitment inside the parent's coinbase, the protocol uses a recognisable byte pattern. Dogecoin's source defines a merged-mining header constant beginning with the bytes 0xfa 0xbe followed by the letters 'mm'. Each auxiliary chain also has a chain ID, which in Dogecoin's parameters is 98 (0x0062), and the code enforces it strictly. The ID prevents a proof prepared for one chain from being replayed on another.
Why it matters to miners
Litecoin is the typical parent for the Scrypt family, and Dogecoin accepts its proof of work through this mechanism. A miner pointed at a pool that supports merged mining earns on each chain separately, using the same hashes. Each chain keeps its own difficulty, rewards and block times.
Example
A Litecoin-compatible miner builds a Litecoin block whose coinbase also commits to a Dogecoin block. If the hash meets Dogecoin's easier target but not Litecoin's, the miner submits the same work to Dogecoin and earns a Dogecoin block reward without hashing again.
Put it into practice
Get paid on every merged chain
A merged-mining payout needs a receive address for each coin. Scrypt Wallet gives you one per coin so Litecoin and Dogecoin rewards both land under keys you hold.
Create a free wallet Get Scrypt for AndroidFrequently asked questions
Is AuxPoW the same as merged mining?
Merged mining is the practice; AuxPoW is the data structure and rules that make the auxiliary chain accept the parent's work.
Does the parent chain change?
No. Parent-chain nodes see an ordinary block with extra bytes in the coinbase and do not need to know about the auxiliary chain.
Does the auxiliary chain share the parent's difficulty?
No. Each chain sets its own target, so the same hash can satisfy one chain and not the other.
Written by the Scrypt Wallet team · Updated 2026-10-02. General education, not financial, tax or legal advice.