Java Card is a Java running environment developed for lowend embedded systems such as smart cards. In this context of scarce resources, ROM size plays a very important role and compression techniques help reducing program sizes as much as possible. Dictionary compression is the most promising technique and has been taken in consideration in this field by several authors.Java Card can adopt a dictionary compression scheme, substituting repeated sequences of bytecodes with new macros stored into a dictionary. This approach does not break the Java Card standard, but requires the use of an ad hoc Java virtual machine and an additional custom component in the converted applet (CAP) file. This paper presents two derived compaction techniques and discusses two scenarios: the first adopts an adaptive (dynamic) dictionary, while the second uses a static one. Although the base dictionary compression technique performs better with an adaptive dictionary, the two proposed techniques perform very close to the base one with a static dictionary. Moreover, we present a different compression mechanism based on re-engineering the CAP file through subroutines. This last technique achieves a higher compression rate, but it is fully compliant with the existing Java Card environments.

Java Cards [4][5] are small resource-constrained embedded systems that have to fulfill rigorous security requirements. Multiple application scenarios demand diverse product performance profiles which are targeted towards markets such as banking applications and mobile applications. In order to tailor the products to the customer's needs we implemented a Software Product Line (SPL). This paper reports on the industrial case of an adoption to a SPL during the development of a highly-secure software system. In order to provide a scientific method which allows the description of research in the field, we apply Action Research (AR). The rationale of AR is to foster the transition of knowledge from a mature research field to practical problems encountered in the daily routine. Thus, AR is capable of providing insights which might be overlooked in a traditional research approach. In this paper we follow the iterative AR process, and report on the successful transfer of knowledge from a research project to a real industrial application.

Java Card is a Java running environment tailored for smart cards. In such small systems, resources are limited, and keeping application size as small as possible is a first order issue. Dictionary compression is a promising technique taken into consideration by several authors. The main drawback of this technique is a degradation in the execution speed. In this paper we propose combining the dictionary compression with another compression technique based on the folding mechanism; the latter is less effective in terms of space savings, but has the advantage of speeding up the execution. A combination of the two techniques leads to higher space savings with a very low decrease in execution time compared with the plain dictionary compression.

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