Quick answer: use Argon2i, unless you have very special needs.<p>&quot;Argon2i uses data-independent memory access, which is preferred for password hashing and password-based key derivation. Argon2i is slower as it makes more passes over the memory to protect from tradeoff attacks.&quot;<p>&quot;Argon2d is faster and uses data-depending memory access, which makes it suitable for cryptocurrencies and applications with no threats from side-channel timing attacks.&quot;<p>The IETF draft is here: <a href="https:&#x2F;&#x2F;tools.ietf.org&#x2F;html&#x2F;draft-josefsson-argon2-00" rel="nofollow">https:&#x2F;&#x2F;tools.ietf.org&#x2F;html&#x2F;draft-josefsson-argon2-00</a>