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    "A study on Tamper-Resistant Software"

    The way of software distribution has been changing with the rapid spread of computer networks such as the Internet. Namely, although almost all of conventional software distribution was in binary code form, but now it is becoming more common to circulate software in source code form.
    In such situations, malicious users can analyze software programs distributed over a network and extract secret information and/or proprietary algorithms from them.

    Consequently realization of software with software obfuscation, which transforms a program into a tamper-resistant form. And software obfuscation has been vigorously studied so far.

    Unfortunately previous software obfuscation techniques share a major drawback that they are not given a theoretical basis and it is still unclear how effective they are.

    In 2000, Wang et al. proposed a software obfuscation technique based on the fact that aliases in a program drastically reduce the precision of static analysis of the program. However, their approach is limited to the \emph{intraprocedural analysis}. Since a program consists of many procedures in general, whether or not it is obfuscated, we must conduct \emph{interprocedural analysis} in order to understand it more accurately.

    That is,since interprocedural analysis is essentially difficult to accomplish, even a little application of such an obfuscation technique to a program can be quite effective.

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