Ethash

Ethash is the planned PoW algorithm for Ethereum 1.0. It is the latest version of Dagger-Hashimoto, although it can no longer appropriately be called that since many of the original features of both algorithms have been drastically changed in the last month of research and development. ¹

Ethash PoW is memory hard, making it basically ASIC resistant. This basically means that calculating the PoW requires choosing subsets of a fixed resource dependent on the nonce and block header. This resource (a few gigabyte size data) is called a DAG. The DAG is totally different every 30000 blocks (a 100 hour window, called an epoch).²

[1] https://github.com/ethereum/wiki/wiki/Ethash

[2] https://ethereum.gitbooks.io/frontier-guide/content/mining.html