How Do Merged Mining and Auxiliary Proof-of-Work (AuxPoW) Help Secure Smaller Coins?

Merged mining allows a miner to mine two different cryptocurrencies simultaneously using the same hashrate, provided the coins share the same mining algorithm. AuxPoW is the technical implementation that enables this.

The smaller coin (AuxPoW chain) piggybacks on the security of the larger coin (parent chain). This dramatically increases the hashrate securing the smaller coin at minimal extra cost to the miners, making a 51 percent attack against the smaller coin significantly more expensive and less likely.

Litecoin and Dogecoin use this mechanism.