> the identity is as secure as a password in a password keeper or authentication key So, not very secure. Passwords aren't very secure on its own and practical

> the identity is as secure as a password in a password keeper or authentication key So, not very secure. Passwords aren't very secure on its own and practically always supplemented by human support systems and alternative factors of authentication. In really critical systems like government, these supplements extend all the way to a physical meeting with a bureaucrat. What's my recourse if I lose my blockchain secret? All of that is the main cost of a serious user authentication system. Who cares if the msg.sender field is guaranteed to be consistent with the sender of a transaction if no one knows who the sender actually is.