Argon2id is a memory-hard password-processing function that makes each attempted secret more costly to evaluate by requiring both computation and memory.
Why a vault needs more than a fast hash
A device may need to derive access from a pattern or password. If each guess were extremely cheap, an attacker with suitable encrypted data could try many candidates quickly. Argon2id is designed to impose a memory and processing cost on that work. RFC 9106 describes the function, its variants, and implementation test vectors.
The chosen parameters matter. The function's name alone does not reveal the memory allocation, number of passes, platform constraints, or rate-limiting behavior of an app. Those details belong in an implementation assessment rather than a marketing promise.
More expensive guesses are still guesses
A common pattern can remain a poor secret. A person who saw you draw it may not need to perform an offline attack at all. Neither Argon2id nor a large pattern grid protects a recovery phrase photographed beside the phone.
Use an uncommon pattern and protect it from observation. Keep the recovery material separate, and treat suspected device compromise as a different problem from guessing resistance.
How this relates to NullVault
NullVault describes Argon2id as part of local pattern processing, alongside encryption and platform-protected key material. It is not an online account password reset mechanism. Read the architecture for the documented boundaries and PBKDF2 versus Argon2id for the broader comparison. The pattern access feature explains what a pattern selects in the interface.