MAC, KDF & password hashingRecommended

Argon2id

Memory-hard password hashing

How it works

Argon2 won the Password Hashing Competition in 2015 and is specified in RFC 9106. It has three variants: Argon2d (resists GPU cracking), Argon2i (resists side-channel attacks) and Argon2id, a hybrid that RFC 9106 recommends as the default. Defenders tune memory, time and parallelism to make each guess costly.

Sizes: Configurable memory, iterations and parallelism

Strengths

Memory-hard and tunable
First choice in the OWASP Password Storage Cheat Sheet
Hybrid variant balances side-channel and GPU resistance

Weaknesses and known attacks

Not FIPS-approved
Memory settings must be sized against server capacity and login rate limits

Use it for

Password storage in new systems
Deriving keys from passphrases

Don't use it for

FIPS-only systems (use PBKDF2)

Exam tip

Argon2id is the modern recommended password hash. Hashing passwords with plain SHA-256, even with a salt, is the wrong answer.

References

Go deeper

scrypt

Memory-hard password hashing and key derivation

bcrypt

Password hashing

PBKDF2

Password-based key derivation and password hashing

Salt

Making every password hash unique

Key stretching

Making weak passwords costly to guess