The most common method used for authentication istextual password, graphical passwords, biometrics etc. .Thevulnerabilities of this method like eves dropping, dictionaryattack, social engineering and shoulder surfing are wellknown. The alternative techniques are graphical passwordsand biometrics. But these two techniques have their owndisadvantages. Biometrics, such as finger prints, iris scan orfacial recognition have been introduced but not yet widelyadopted as major drawback of this approach is that suchsystems can be expensive and the identification process can beslow. There are many graphical password schemes that areproposed but the drawback to this is most of them suffer fromshoulder surfing and usability issues or taking more time foruser to login or having tolerance. Personal Digital Assistantsare being used by the people to store their personal andconfidential information like passwords and PIN numbers.Authentication should be provided for the usage of thesedevice. In this Project, a new authentication scheme isproposed for PDAs. These schemes authenticate the user bysession passwords. Session passwords are passwords that areused only once. Once the session is terminated, the sessionpassword is no longer useful. For every login process, usersinput different passwords. The session passwords providebetter security against dictionary and brute force attacks aspassword changes for every session. The proposedauthentication schemes use text and colors for generatingsession passwords.