Modern information and distributed systems runs for extensive periods of time and are being constantly improved in service objectives under evolving technologies and changing regulations and standards. These systems have become extremely complex and therefore, it is very important that they are to be dependable in order for them to execute their functionalities and purposes correctly or to an acceptable level of services. However, due to the ever-growing complexity of information and distributed systems, it is very difficult to achieve dependability by relying only on conventional technologies such as development processes and formal methods. And therefore the idea of Assurance Case or D-Case (dependability case) has become more and more a popular notion. Recently, D-Case which is an extension form of Assurance Case, is more commonly associated with the safely aspect of dependability. And because of this regard, safety cases are more well known in comparison to other aspects of dependability such as availability, integrity and confidentiality witch are all related to the security domain. In this paper, we introduce our new approach to the development of a dependable security case.