The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform

Tobias Nipkow - One of the best experts on this subject based on the ideXlab platform.

  • TPHOLs - Certifying Machine Code Safety: Shallow Versus Deep Embedding
    Lecture Notes in Computer Science, 2004
    Co-Authors: Martin Wildmoser, Tobias Nipkow
    Abstract:

    We formalise a simple assembly language with procedures and a safety policy for Arithmetic Overflow in Isabelle/HOL. To verify individual programs we use a safety logic. Such a logic can be realised in Isabelle/HOL either as shallow or deep embedding. In a shallow embedding logical formulas are written as HOL predicates, whereas a deep embedding models formulas as a datatype. This paper presents and discusses both variants pointing out their specific strengths and weaknesses.

  • certifying machine code safety shallow versus deep embedding
    Lecture Notes in Computer Science, 2004
    Co-Authors: Martin Wildmoser, Tobias Nipkow
    Abstract:

    We formalise a simple assembly language with procedures and a safety policy for Arithmetic Overflow in Isabelle/HOL. To verify individual programs we use a safety logic. Such a logic can be realised in Isabelle/HOL either as shallow or deep embedding. In a shallow embedding logical formulas are written as HOL predicates, whereas a deep embedding models formulas as a datatype. This paper presents and discusses both variants pointing out their specific strengths and weaknesses.

  • IFIP TCS - Prototyping Proof Carrying Code
    IFIP International Federation for Information Processing, 1
    Co-Authors: Martin Wildmoser, Tobias Nipkow, Gerwin Klein, Sebastian Nanz
    Abstract:

    We introduce a generic framework for proof carrying code, developed and mechanically verified in Isabelle/HOL. The framework defines and proves sound a verification condition generator with minimal assumptions on the underlying programming language, safety policy, and safety logic. We demonstrate its usability for prototyping proof carrying code systems by instantiating it to a simple assembly language with procedures and a safety policy for Arithmetic Overflow.

Martin Wildmoser - One of the best experts on this subject based on the ideXlab platform.

  • TPHOLs - Certifying Machine Code Safety: Shallow Versus Deep Embedding
    Lecture Notes in Computer Science, 2004
    Co-Authors: Martin Wildmoser, Tobias Nipkow
    Abstract:

    We formalise a simple assembly language with procedures and a safety policy for Arithmetic Overflow in Isabelle/HOL. To verify individual programs we use a safety logic. Such a logic can be realised in Isabelle/HOL either as shallow or deep embedding. In a shallow embedding logical formulas are written as HOL predicates, whereas a deep embedding models formulas as a datatype. This paper presents and discusses both variants pointing out their specific strengths and weaknesses.

  • certifying machine code safety shallow versus deep embedding
    Lecture Notes in Computer Science, 2004
    Co-Authors: Martin Wildmoser, Tobias Nipkow
    Abstract:

    We formalise a simple assembly language with procedures and a safety policy for Arithmetic Overflow in Isabelle/HOL. To verify individual programs we use a safety logic. Such a logic can be realised in Isabelle/HOL either as shallow or deep embedding. In a shallow embedding logical formulas are written as HOL predicates, whereas a deep embedding models formulas as a datatype. This paper presents and discusses both variants pointing out their specific strengths and weaknesses.

  • IFIP TCS - Prototyping Proof Carrying Code
    IFIP International Federation for Information Processing, 1
    Co-Authors: Martin Wildmoser, Tobias Nipkow, Gerwin Klein, Sebastian Nanz
    Abstract:

    We introduce a generic framework for proof carrying code, developed and mechanically verified in Isabelle/HOL. The framework defines and proves sound a verification condition generator with minimal assumptions on the underlying programming language, safety policy, and safety logic. We demonstrate its usability for prototyping proof carrying code systems by instantiating it to a simple assembly language with procedures and a safety policy for Arithmetic Overflow.

Oliver Baur - One of the best experts on this subject based on the ideXlab platform.

  • Spheroidal and ellipsoidal harmonic expansions of the gravitational potential of small Solar System bodies. Case study: Comet 67P/Churyumov‐Gerasimenko
    Journal of Geophysical Research: Planets, 2016
    Co-Authors: Stefan Reimond, Oliver Baur
    Abstract:

    Gravitational features are a fundamental source of information to learn more about the interior structure and composition of planets, moons, asteroids and comets. Gravitational field modeling typically approximates the target body with a sphere, leading to a representation in spherical harmonics. However, small celestial bodies are often irregular in shape, and hence poorly approximated by a sphere. A much better suited geometrical fit is achieved by a tri-axial ellipsoid. This is also mirrored in the fact that the associated harmonic expansion (ellipsoidal harmonics) shows a significantly better convergence behavior as opposed to spherical harmonics. Unfortunately, complex mathematics and numerical problems (Arithmetic Overflow) so far severely limited the applicability of ellipsoidal harmonics. In this paper, we present a method that allows expanding ellipsoidal harmonics to a considerably higher degree compared to existing techniques. We apply this novel approach to model the gravitational field of comet 67P, the final target of the Rosetta mission. The comparison of results based on the ellipsoidal parameterization with those based on the spheroidal and spherical approximations reveals that the latter is clearly inferior; the spheroidal solution, on the other hand, is virtually just as accurate as the ellipsoidal one. Finally, in order to generalize our findings, we assess the gravitational field modeling performance for some 400 small bodies in the solar system. From this investigation we generally conclude that the spheroidal representation is an attractive alternative to the complex ellipsoidal parameterization on the one hand, and the inadequate spherical representation on the other hand.

Stefan Reimond - One of the best experts on this subject based on the ideXlab platform.

  • Spheroidal and ellipsoidal harmonic expansions of the gravitational potential of small Solar System bodies. Case study: Comet 67P/Churyumov‐Gerasimenko
    Journal of Geophysical Research: Planets, 2016
    Co-Authors: Stefan Reimond, Oliver Baur
    Abstract:

    Gravitational features are a fundamental source of information to learn more about the interior structure and composition of planets, moons, asteroids and comets. Gravitational field modeling typically approximates the target body with a sphere, leading to a representation in spherical harmonics. However, small celestial bodies are often irregular in shape, and hence poorly approximated by a sphere. A much better suited geometrical fit is achieved by a tri-axial ellipsoid. This is also mirrored in the fact that the associated harmonic expansion (ellipsoidal harmonics) shows a significantly better convergence behavior as opposed to spherical harmonics. Unfortunately, complex mathematics and numerical problems (Arithmetic Overflow) so far severely limited the applicability of ellipsoidal harmonics. In this paper, we present a method that allows expanding ellipsoidal harmonics to a considerably higher degree compared to existing techniques. We apply this novel approach to model the gravitational field of comet 67P, the final target of the Rosetta mission. The comparison of results based on the ellipsoidal parameterization with those based on the spheroidal and spherical approximations reveals that the latter is clearly inferior; the spheroidal solution, on the other hand, is virtually just as accurate as the ellipsoidal one. Finally, in order to generalize our findings, we assess the gravitational field modeling performance for some 400 small bodies in the solar system. From this investigation we generally conclude that the spheroidal representation is an attractive alternative to the complex ellipsoidal parameterization on the one hand, and the inadequate spherical representation on the other hand.

Christian Reitwiessner - One of the best experts on this subject based on the ideXlab platform.

  • ISoLA (4) - SMT-Based Verification of Solidity Smart Contracts
    Lecture Notes in Computer Science, 2018
    Co-Authors: Leonardo Alt, Christian Reitwiessner
    Abstract:

    Ethereum smart contracts are programs that run inside a public distributed database called a blockchain. These smart contracts are used to handle tokens of value, can be accessed and analyzed by everyone and are immutable once deployed. Those characteristics make it imperative that smart contracts are bug-free at deployment time, hence the need to verify them formally. In this paper we describe our current efforts in building an SMT-based formal verification module within the compiler of Solidity, a popular language for writing smart contracts. The tool is seamlessly integrated into the compiler, where during compilation, the user is automatically warned of and given counterexamples for potential Arithmetic Overflow/underflow, unreachable code, trivial conditions, and assertion fails. We present how the component currently translates a subset of Solidity into SMT statements using different theories, and discuss future challenges such as multi-transaction and state invariants.