Abstract

Sharing and transfer of references is difficult to control in object-oriented languages. As information security is increasingly becoming software dependent, this difficulty poses serious problems for writing secure components. In this paper, we present a set of inexpensive syntactic constraints that strengthen encapsulation in object-oriented programs and facilitate the implementation of secure systems. We introduce two mechanisms: con ned types to impose static scoping on dynamic object references and anonymous methods which do not reveal the identity of the current instance (this). Confined types protect objects from use by untrusted code, while anonymous methods allow standard classes to be reused from con ned classes. We have implemented a verifier which performs a modular analysis of Java programs and provides a static guarantee that confinement is respected. We present security related programming examples.

Citations