Abstract
At present, to access to email account or bank account, a network user has to remember the
registered account number of the user and the corresponding password for every service with which
they are registered. However, when multiple systems are involved, the user is then required to
authenticate to each system individually and repeatedly. It results in inconvenience to each
authentication. Recently, to overcome the problem, a single-sign-on (SSO) scheme was proposed to
achieve user identification and authentication to multiple security-protected systems simultaneously
through a single operation. We surveyed various papers to know the basic concept of SSO. In this paper
we have to use cloud model, its key challenges and short intro of SSO.