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).

Argon2 has three variants: Argon2i, Argon2d, and Argon2id.

• Argon2d is faster and uses data-depending memory access, which makes it highly resistant against GPU cracking attacks and suitable for applications with no threats from side-channel timing attacks (eg. cryptocurrencies).
• Argon2i instead uses data-independent memory access, which is preferred for password hashing and password-based key derivation, but it is slower as it makes more passes over the memory to protect from tradeoff attacks.
• Argon2id is a hybrid of Argon2i and Argon2d, using a combination of data-depending and data-independent memory accesses, which gives some of Argon2i's resistance to side-channel cache timing attacks and much of Argon2d's resistance to GPU cracking attacks.