Argon2 for local master password hashing (not encryption key derivation)

Hello! First of all, I really appreciate for this great port of Bitwarden in Rust! I am a bit new to here, but I read the source code and found that (somewhat legacy) PBKDF2 is used for "local master password hashing." Of course, I really understand that the encryption key is still derived by PBKDF2 due to compatibility with original Bitwarden and for compatibility with various frontends like iOS/Android Apps (see So I know it is tough to quickly change the algorithm to modern one for the encryption key derivation. On the other hand, I think that in current era, since local password hashing has no compatibility issue with Bitwarden, Argon2 could be better in terms of "modern" cryptography, whereas PBKDF2 is still no problem. I actually implemented the Argon2 version of Vaultwarden by myself in my forked repo ( and it works with no problem at this point. It can also compatible with existing users with PBKDF2 password hashing, and they can migrate to Ar…