With the proliferation of mobile, wireless and internet enabled devices (e.g. PDAs, cell phones, pagers, etc.), Java is emerging as a standard execution environment due to its security, portability, mobility and network support features. The platform of choice in this setting is J2ME CLDC.
The typical most widely deployed J2ME CLDC platform consists of several components that can be classified into: Virtual machine, APIs and tools. The virtual machine is the KVM. The APIs are CLDC and MIDP. The tools are the pre-verifier and the Java Code Compacter (JCC). KVM (Kilobyte Virtual Machine) is an implementation of the Java Virtual Machine (JVM).
It lies on top of the host operating system and its main goal is to execute compiled program units (class files). CLDC provides the most basic set of libraries and virtual-machine features for resource-constrained, network-connected devices. MIDP is a layer on top of CLDC configuration.
It extends the latter with more specific capabilities, namely, networking, graphics, security, application management, and persistent storage. The preverifier checks all the Java classes to enforce object, stack and control-flow safety. This is done off-line and the result is stored as attributes in the compiled program units.
The Java code compactor (JCC) is in charge of the romizing process. The latter is a feature of KVM that allows loading and linking Java classes at startup. The idea is to create an image of these classes in a file and finally to link the image with KVM. With the large number of applications that could be available for Java enabled devices, security is of paramount importance.
Currently, viruses for phones start to emerge (e.g. Cabir), a number of model specific attacks has been reported (e.g. Nokia 6210 DoS, Siemens S55 SMS, etc.), and mobile attacks.
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