To login your password + username + public salt are hashed using scrypt hashing function (with parameters 17, 8, 1, 64). The output of this is your login keypair and a symmetric key. The login keypair is used to auth with your server and retrieve your encrypted login data, which is decrypted using the aforementioned symmetric key. The login data contains your identity keypair, social keypair, and the root capability to your filesystem.