Clean UI/UX and really neat exploration of how to map pubkey auth to existing expectations.
Security details are here: https://github.com/bigmarh/nostrpass/blob/main/docs/SECURITY_AND_PERMISSIONS.md
afaict they password encrypt a private key and store it in indexeddb. They use BIP32 to derive multiple identities. When the password is provided they decrypt the private key in a web worker which has a simple interface.
They also support traditional recovery questions whose answers are composed into some kind of recovery key.