This is the reference C implementation of Argon2, the password-hashing function that won the Password Hashing Competition (PHC). Argon2 is a password-hashing function that summarizes the state of the art in the design of memory-hard functions and can be used to hash passwords for credential storage, key derivation, or other applications. It has a simple design aimed at the highest memory filling rate and effective use of multiple computing units, while still providing defense against tradeoff attacks (by exploiting the cache and memory organization of the recent processors).