  Password authentication is a common approach to the system security and it is
also a very important procedure to gain access to user resources. In the
conventional password authentication methods a server has to authenticate the
legitimate user. In our proposed method users can freely choose their passwords
from a defined character set or they can use a graphical image as password and
that input will be normalized. Neural networks have been used recently for
password authentication in order to overcome pitfall of traditional password
authentication methods. In this paper we proposed a method for password
authentication using alphanumeric password and graphical password. We used Back
Propagation algorithm for both alphanumeric (Text) and graphical password by
which the level of security can be enhanced. This paper along with test results
show that converting user password in to Probabilistic values enhances the
security of the system
