Lessons learned on implementing ECDSA on a Java smart card

Many companies have designed and manufactured smart cards, which vary greatly in both the hardware they use and software development environments they provide. Java Card promises to make smart card programming easier, by introducing a common programming language and run–time environment. Also as a member of the Java family, Java Card raises up hopes of easy software portability from PCs to smart cards. Our work demonstrates, that this promise is not fulfilled in the majority of the cases because of different memory models. The portability of code from other JVMs to Java Card is an important issue, which requires, among other things, a systematic method of conserving memory on the card. In our work we developed such an approach by constructing variable interference graphs and graph coloring them to minimize the number of temporary variables. The concrete method is a modified register allocation approach, which has traditionally been used in compiler design. This is followed by numerical performance data of the actual prototype along with the analysis of that data.