idate message: <ValidateRequest> 4: Request status information of X.509 certificate 5: Response status information of X.509 certificate 6: SOAP response message - signed certificate status result 7: Verification of XML signature 8: Parsing the result response message and gets <StatusValue= .."> Figure 11.6 Procedure for validation of X.509 certificate using the XKMS server. On Secure JAVA Mobile Application 4. In order to validate the received X.509v3 certificate, the XKMS server com- municates with the PKI server beyond that publishes CRL (or uses the OCSP). 5. PKI server responds with status information about received X.509v3 certificate. 6. The XMKS server creates the XML response message and generates a corre- sponding XML signature and sends it to the mobile user. 7. The mobile application receives the ValidateResult message and verifies the XML signature. 8. If the signature verification is successful, the secure JAVA mobile application parses the received result message and gets information about a StatusValue of the requested X.509v3 certificate. If the received StatusValue of the requested X.509v3 certificate is correct, then the secure JAVA application finalized successfully the verification of the signature of the received signed document. If the signer's certificate is not included in the signed message, the Locate request function should be done (based on some appropriate information about a location where this certificate could be found (e.g., some URL)) before using the Validate request function in order to get the appropriate PKI certificate from the XKMS server. Also, the Locate request could be used to request a corresponding PKI certifi- cate from the XKMS server in order to be able to perform encryption functionality (encryption part of the WS-security or XML-security) of some XML or SOAP messages. All testing and simulations of the mentioned functionalities of the XKMS pro- tocol are implemented by using a simulator for the development of JAVA applica- tion supporting also the mobile phones: 