1. KVM Class File Verification On Board Verification of Untrusted Classes

2. So no RMI, and no JINI, J2EE, or other RMI based technologies. No sharing of applications among friends No discovery and use of network services which require downloading classes to the client No Mechanism for establishing trustworthiness of classes obtained from untrusted sources

3. Loaded Classes The KVM does minimal verification Loads class file into class data structure Verifies symbolic references Does some checking of byte code Relies on an offline preverifier to check classes before they are put on the device KVM Trusted Classes Class Loader

4. Preverifier Performs the majority of class verification Taken directly from the Sun JVM source code and converted to a standalone program

5. Our Plans

6. On Board Verification Only classes from untrusted sources will need the extra verification All other classes will be managed as they are currently Loaded Classes KVM Trusted Classes Class loader verifier Untrusted classes

7. On Board Verification We will move the preverifier into the KVM for use as a verifier Once a foreign class has been run though it, it is fed to the existing mechanism just like any other class Loaded Classes KVM Trusted Classes Class loader verifier Untrusted classes

8. The preverifier is not optimized for memory savings We will optimize our verifier’s memory usage as much as possible We will use simple measurement tools to determine memory savings We will use a set of test classes to verify that behavior doesn’t change

9. KVM has no mechanism for loading foreign classes We will implement a very simple mechanism in VmExtra In addition to the class path, the desktop version will read from a separate foreign class path Any classes loaded from the foreign class path are subject to verification

10. Things To Do Testing and measurement tools Integrate preverifier with KVM Optimize verifier Add foreign class path to VmExtra Select verification by class source Deliver fully functional and optimized application