c signature in the JAVA application using the private key stored either in JAVA keystore or in PKI SIM smart card. Data are encrypted using a crypto MIDlet or Xlet JAVA application installed on mobile phone with CLDC or Connected Device Configuration (CDC) configura- tions. The user uses standard WS-Signature mechanism (WS-security) to wrap a cryp- tographic signature into the SOAP request and sends the request over to the remote Web Service endpoint implementation. Web Service performs request processing and sends SOAP response back to the JAVA-based mobile phone application. The mobile application processes the SOAP response and displays the status to the mobile user. All servers mentioned in this chapter are deployed as SOAP-based Web Service using the Sun Glassfish application server. On Secure JAVA Mobile Application The user registration process through XMKS service was implemented in J2ME CDC 1.1 environment. We partly modified and used an open-source Apache Trust Services Integration Kit (TSIK) package (http://svn.apache.org/viewvc/incubator/ tsik/) for the implementation of digital signature of XML documents. In the XML signature procedure, we used the 1024-bits RSA key. This document was then sent to an XKMS server using HTTP protocol. For the implementation of HTTP communication, we used mobile phone J2ME- embedded methods that implemented the javax.microedition.io.HttpConnection interface. 11.3.3 Certification Validation Schema XML Key Information Service Specification (X-KISS) is a second part of the XKMS protocol which supports a delegation of the processing of PKI certificates for a purpose of XML-security or WS-security from an application (in this case, it is the secure mobile application) to the XKMS server. In this sense, the secure mobile application will include the following function- alities: Locate or Validate requests as specified by the X-KISS. The Validate request of the X-KISS protocol will be used by the secure mobile application in order to be able to complete the verification of an 