Although the password authentication has been a popular solution so far, it still has many shortages. Users must remember a lot of passwords which are easily shared with other people. Passwords can be stolen when the encrypted transmission line is not used. Besides, if users set passwords with insufficient length or special symbols passwords will be cracked by brute or dictionary attack techniques. The password solution is not able to prevent sniffing and key-logger attacks. It doesn’t guarantee deniability because users register passwords for the service providers who save the passwords. The password authentication solution is one-factor authentication.
This is two-factor authentication solution which does not support non-denial function and digital signatures.