Signature élèctronique +jdk1.6

Bonjour,
en effet, j'ai une applet java qui vérifie la signature client, cette dernière est fonctionnel avec un jdk1.5 et tout qui le précédent, mais en utilisant le jdk1.6 l'exception de signature suivante est générée:

sun.security.validator.ValidatorException: Netscape cert type does not permit use for code signing
at sun.security.validator.EndEntityChecker.checkCodeSigning(Unknown Source)
at sun.security.validator.EndEntityChecker.check(Unknown Source)
at sun.security.validator.Validator.validate(Unknown Source)
at sun.security.validator.Validator.validate(Unknown Source)
at com.sun.deploy.security.TrustDecider.isAllPermissionGranted(Unknown Source)
at com.sun.deploy.security.TrustDecider.isAllPermissionGranted(Unknown Source)
at sun.plugin.security.PluginClassLoader.getPermissions(Unknown Source)
at java.security.SecureClassLoader.getProtectionDomain(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at sun.applet.AppletClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadCode(Unknown Source)
at sun.applet.AppletPanel.createApplet(Unknown Source)
at sun.plugin.AppletViewer.createApplet(Unknown Source)
at sun.applet.AppletPanel.runLoader(Unknown Source)
at sun.applet.AppletPanel.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

merci de vérifier avec moi cette erreur et de votre aide