How to implement Digital Signature in J2ME

[jayantb]

What i want to do is :

1) Install digital signed testing certificate in my mobile device (using S60).

2) Create a SMS sending form in midlet.

3) Digitally signed the information using installed certificate before sending via SMS sending form.

How would do this??

What i've done till:

1) I've installed a certificate from this link http://www.aloaha.com/wi-software-en/aloaha-pki.php.

2) I used following midlet as example:

import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;
import javax.microedition.securityservice.CMSMessageSignatureService;
import javax.microedition.securityservice.CMSMessageSignatureServiceException;
import javax.microedition.io.file.FileConnection;
import javax.microedition.io.file.FileSystemRegistry;
import java.io.OutputStream;
import java.util.Enumeration;
import javax.microedition.io.Connector;

public class PaymentAuthorization extends MIDlet implements CommandListener {

    Display display = null;
    List employeeList = null;
    String[] employeeArray = {"Derrick Johnson, 40 hrs", "James Williams, 44 hrs", "Tirrell Payton, 42 hrs", "William Bean, 20 hrs"};
    Form progressForm = null;
    Command authCommand = null;
    Command denyCommand = null;
    Command exitCommand = null;
    String originalMessage = null;
    byte[] signedMessage = null;
    String signedMessageFile = "paymentAuthorization.dat";

    public PaymentAuthorization(){
        employeeList = new List("Payment Authorization", List.IMPLICIT, employeeArray, null);
        employeeList.setCommandListener(this);
        authCommand = new Command("Authorize", Command.OK, 0);
        denyCommand = new Command("Deny", Command.OK, 0);
        exitCommand = new Command("Exit", Command.EXIT, 1);
        employeeList.addCommand(authCommand);
        employeeList.addCommand(denyCommand);
        progressForm = new Form("Signing Progress");
        progressForm.addCommand(exitCommand);
        progressForm.setCommandListener(this);
    }

    public void startApp() {
        display = Display.getDisplay(this);
        display.setCurrent(employeeList);
    }

    public void pauseApp() {
    }

    public void destroyApp(boolean unconditional) {
    }

    public void commandAction(Command command, Displayable d) {
        if (command == exitCommand) {
            destroyApp(true);
            notifyDestroyed();
        } else {

            display.setCurrent(progressForm);
            originalMessage = employeeArray[employeeList.getSelectedIndex()] + ", " + command.getLabel();

            new Thread() {
                    public void run() {
                        progressForm.append("Sign test started ...\n");
                        System.out.println("Sign test started...");
                        signMessage();
                        progressForm.append("Sign test finished.\n");
                        System.out.println("Sign test finished.");
                    }
           }.start();
        }

    }

    private void signMessage() {       
        String caName = "c=US,o=Aloaha Certification Authority,cn=Aloaha Certification Authority";
        String[] caNames = new String[1];
        String userPrompt = "Please insert the proper security element ";
        caNames[0] = caName;
        try {            
            signedMessage = CMSMessageSignatureService.sign(originalMessage,CMSMessageSignatureService.SIG_INCLUDE_CERTIFICATE | CMSMessageSignatureService.SIG_INCLUDE_CONTENT, caNames, userPrompt);
           
            FileConnection fileConnection = null;
            OutputStream outputStream = null;
            try{
                Enumeration e = FileSystemRegistry.listRoots();
                String rootName = (String) e.nextElement ();
                String galleryPath = System.getProperty("fileconn.dir.photos");
                fileConnection = (FileConnection)Connector.open(galleryPath + signedMessageFile);
                if (fileConnection.exists() == false){
                    fileConnection.create();
                }
                outputStream = fileConnection.openOutputStream();
                outputStream.write(signedMessage);
                outputStream.flush();
                outputStream.close();
                fileConnection.close();
            } catch (Exception e){
                System.out.println("Error creating file");
                e.printStackTrace();
            }

        } catch (IllegalArgumentException iae) {
            // Perform error handling
            iae.printStackTrace();
        } catch (CMSMessageSignatureServiceException ce) {
            if (ce.getReason() == CMSMessageSignatureServiceException.CRYPTO_FORMAT_ERROR) {
                System.out.println("Error formatting signature.");
            } else {
                System.out.println(ce.getMessage());
            }
        } catch (Exception e) {
            System.out.println("Other exception: " + e);
        }
    }
}

3) While running this midlet. I'm unable to create .dat file. Even, file connection code is not executing.. as it is not showing any security exception regading file connection.


Thanks!!!