We introduce Jinja, a Java-like programming language with a formal semantics designed to exhibit core features of the Java language architecture. Jinja is a compromise between realism of the language and tractability and clarity of the formal semantics. The following aspects are formalised: a big and a small step operational semantics for Jinja and a proof of their equivalence; a type system and a definite initialisation analysis; a type safety proof of the small step semantics; a virtual machine (JVM), its operational semantics and its type system; a type safety proof for the JVM; a bytecode verifier, i.e. data flow analyser for the JVM; a correctness proof of the bytecode verifier w.r.t. the type system; a compiler and a proof that it preserves semantics and well-typedness. The emphasis of this work is not on particular language features but on providing a unified model of the source language, the virtual machine and the compiler. The whole development has been carried out in the theorem prover Isabelle/HOL.

Bytecode verification is a crucial security component for Java applets, on the Web and on embedded devices such as smart cards. This paper reviews the various bytecode verification algorithms that have been proposed, recasts them in a common framework of dataflow analysis, and surveys the use of proof assistants to specify bytecode verification and prove its correctness.

A fundamental problem in software-based security is whether local security checks inserted into the code are sufficient to implement a global security property. We introduce a formalism based on a two-level linear-time temporal logic for specifying global security properties pertaining to the control-flow of the program, and illustrate its expressive power with a number of existing properties. We define a minimalistic, security-dedicated program model that only contains procedure call and run-time security checks and propose an automatic method for verifying that an implementation using local security checks satisfies a global security property. For a given formula in the temporal logic we prove that there exists a bound on the size of the states that have to be considered in order to assure the validity of the formula: this reduces the problem to finite-state model checking. Finally, we instantiate the framework to the security architecture proposed for Java (JDK 1.2).

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This article presents a novel approach to the problem of bytecode verification for Java Card applets. By relying on prior off-card bytecode transformations, we simplify the bytecode verifier and reduce its memory requirements to the point where it can be embedded on a smart card, thus increasing significantly the security of post-issuance downloading of applets on Java Cards.

Abstract. Proof-Carrying Code (PCC) is a general approach to mobile code safety in which programs are augmented with a certificate (or proof). The practical uptake of PCC greatly depends on the existence of a variety of enabling technologies which allow both to prove programs correct and to replace a costly verification process by an efficient checking procedure on the consumer side. In this work we propose Abstraction-Carrying Code (ACC), a novel approach which uses abstract interpretation as enabling technology. We argue that the large body of applications of abstract interpretation to program verification is amenable to the overall PCC scheme. In particular, we rely on an expressive class of safety policies which can be defined over different abstract domains. We use an abstraction (or abstract model) of the program computed by standard static analyzers as a certificate. The validity of the abstraction on the consumer side is checked in a single-pass by a very efficient and specialized abstract-interpreter. We believe that ACC brings the interpretation techniques to the area of mobile code safety. We have implemented and benchmarked ACC within the Ciao system preprocessor. The experimental results show that the checking phase is indeed faster than the proof generation phase, and that the sizes of certificates are reasonable. 1

The Java security policy is implemented by security components such as the Java Virtual Machine (JVM), the API, the verifier, the loader. It is of prime importance to ensure that the implementation of these components is in accordance with their specifications. Formal methods can be used to bring the mathematical proof that the implementation of these components corresponds to their specification. In this paper, a formal development is performed on the Java Card byte code verifier using the B method. The whole Java Card language is taken into account in order to provide realistic metrics on formal development. The architecture and the tricky points of the development are presented. This formalization leads to an embeddable implementation of the byte code verifier thanks to automatic code translation from formal implementation into C code. We present the formal models, discuss the integration into the card and the results of such an experiment.

Java is a popular development platform for mobile code systems. It ensures application portability and mobility for a variety of systems, while providing strong security features. The intermediate code (byte code) allows the virtual machine to verify statically (during the loading phase) that the program is well-behaved. This is done by a software security module called the byte code verifier. Smart Cards that provide a Java Virtual Machine, called Java Card, are not supplied with such a verifier because of its complexity. Alternatives are being studied to provide the same functionality outside the card. In the present paper, we propose to integrate the whole verifier inside the smart card. This ensures that the smart card becomes entirely autonomous, which allows full realization of smart cards potential as pervasive computing devices. Our verifier uses a specialized encoding and a software cache with a variety of cache polices to adapt to the hardware constraints of smart card. Our experimental results confirm the feasibility of such a security system being implemented in a smart card.

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Abstract. Eva and Kristoffer Rose proposed a (sparse) annotation of Java Virtual Machine code with types to enable a one-pass verification of welltypedness. We have formalized a variant of their proposal in the theorem prover Isabelle/HOL and proved soundness and completeness. 1