s of development the secure JAVA Mobile Application we have used the J2ME development environment. The J2ME is a runtime environment for On Secure JAVA Mobile Application resource-constrained environments and development. J2ME includes specific virtual machines, configurations, and profiles for various environments and needs. With an appropriate configuration and profile, J2ME applications could be exe- cuted within pagers, mobile phones, Personal Digital Assistants (PDAs), set-top boxes, and automobile navigation systems, just to mention some [2]. This chapter mainly identifies the need for security in mobile communications, such as mentioned in [3]. It mainly presents a secure mobile framework that is based on widely used XML-based standards and technologies such as XML-Signature, XML-Encryption (XML-security), and Web Services Security (WS-security). It describes the main entities that participate in the communication, and illustrates its operation with a fully deployed mobile scenario. Besides security aspects of the XML communication, a possible Federation ID system based on Security Token Service (STS) is considered. The security token represents a collection of claims about an entity. Typically, this token is used to authenticate the sender or responder in a message transaction. In this work, Security Assertion Markup Language (SAML) tokens/assertions have a role of security tokens. Communication between JAVA mobile application, or the SOA-Based plat- form itself, and STS server is realized by using WS-Secured Simple Object Access Protocol (SOAP) communication. The communication flows in the following way. The JAVA mobile application (or the platform itself) sends the Request for Security Token (RST) to the STS server and, if everything is ok (if the user is successfully authenticated and authorized for using the particular Web Service), receives back the RST Response (RSTR) which consists of the SAML token with the user's role on the proposed e/m-government platform. We also investigated the possibility o