A Hybrid Analysis for Security Protocols with State

Cryptographic protocols rely on message-passing to coordinate activity among principals. Each principal maintains local state in individual local sessions only as needed to complete that session. However, in some protocols a principal also uses state to coordinate its different local sessions. Sometimes the non-local, mutable state is used as a means, for example with smart cards or Trusted Platform Modules. Sometimes it is the purpose of running the protocol, for example in commercial transactions. Many richly developed tools and techniques, based on well-understood foundations, are available for design and analysis of pure message-passing protocols. But the presence of cross-session state poses difficulties for these techniques. In this paper we provide a framework for modeling stateful protocols. We define a hybrid analysis method. It leverages theorem-proving---in this instance, the PVS prover---for reasoning about computations over state. It combines that with an "enrich-by-need" approach---embodied by CPSA---that focuses on the message-passing part. As a case study we give a full analysis of the Envelope Protocol, due to Mark Ryan

Verifying the Interplay of Authorization Policies and Workflow in Service-Oriented Architectures (Full version)

A widespread design approach in distributed applications based on the service-oriented paradigm, such as web-services, consists of clearly separating the enforcement of authorization policies and the workflow of the applications, so that the interplay between the policy level and the workflow level is abstracted away. While such an approach is attractive because it is quite simple and permits one to reason about crucial properties of the policies under consideration, it does not provide the right level of abstraction to specify and reason about the way the workflow may interfere with the policies, and vice versa. For example, the creation of a certificate as a side effect of a workflow operation may enable a policy rule to fire and grant access to a certain resource; without executing the operation, the policy rule should remain inactive. Similarly, policy queries may be used as guards for workflow transitions. In this paper, we present a two-level formal verification framework to overcome these problems and formally reason about the interplay of authorization policies and workflow in service-oriented architectures. This allows us to define and investigate some verification problems for SO applications and give sufficient conditions for their decidability.Comment: 16 pages, 4 figures, full version of paper at Symposium on Secure Computing (SecureCom09

Citizen Electronic Identities using TPM 2.0

Electronic Identification (eID) is becoming commonplace in several European countries. eID is typically used to authenticate to government e-services, but is also used for other services, such as public transit, e-banking, and physical security access control. Typical eID tokens take the form of physical smart cards, but successes in merging eID into phone operator SIM cards show that eID tokens integrated into a personal device can offer better usability compared to standalone tokens. At the same time, trusted hardware that enables secure storage and isolated processing of sensitive data have become commonplace both on PC platforms as well as mobile devices. Some time ago, the Trusted Computing Group (TCG) released the version 2.0 of the Trusted Platform Module (TPM) specification. We propose an eID architecture based on the new, rich authorization model introduced in the TCGs TPM 2.0. The goal of the design is to improve the overall security and usability compared to traditional smart card-based solutions. We also provide, to the best our knowledge, the first accessible description of the TPM 2.0 authorization model.Comment: This work is based on an earlier work: Citizen Electronic Identities using TPM 2.0, to appear in the Proceedings of the 4th international workshop on Trustworthy embedded devices, TrustED'14, November 3, 2014, Scottsdale, Arizona, USA, http://dx.doi.org/10.1145/2666141.266614

In my Wish List, an Automated Tool for Fail-Secure Design Analysis: an Alloy-Based Feasibility Draft

A system is said to be fail-secure, sometimes confused with fail-safe, if it maintains its security requirements even in the event of some faults. Fail-secure analyses are required by some validation schemes, such as some Common Criteria or NATO certifications. However, it is an aspect of security which as been overlooked by the community. This paper attempts to shed some light on the fail-secure field of study by: giving a definition of fail-secure as used in those certification schemes, and emphasizing the differences with fail-safe; and exhibiting a first feasibility draft of a fail-secure design analysis tool based on the Alloy model checker.Comment: In Proceedings ESSS 2014, arXiv:1405.055

Trusted Computing and Secure Virtualization in Cloud Computing

Large-scale deployment and use of cloud computing in industry is accompanied and in the same time hampered by concerns regarding protection of data handled by cloud computing providers. One of the consequences of moving data processing and storage off company premises is that organizations have less control over their infrastructure. As a result, cloud service (CS) clients must trust that the CS provider is able to protect their data and infrastructure from both external and internal attacks. Currently however, such trust can only rely on organizational processes declared by the CS provider and can not be remotely verified and validated by an external party. Enabling the CS client to verify the integrity of the host where the virtual machine instance will run, as well as to ensure that the virtual machine image has not been tampered with, are some steps towards building trust in the CS provider. Having the tools to perform such verifications prior to the launch of the VM instance allows the CS clients to decide in runtime whether certain data should be stored- or calculations should be made on the VM instance offered by the CS provider. This thesis combines three components -- trusted computing, virtualization technology and cloud computing platforms -- to address issues of trust and security in public cloud computing environments. Of the three components, virtualization technology has had the longest evolution and is a cornerstone for the realization of cloud computing. Trusted computing is a recent industry initiative that aims to implement the root of trust in a hardware component, the trusted platform module. The initiative has been formalized in a set of specifications and is currently at version 1.2. Cloud computing platforms pool virtualized computing, storage and network resources in order to serve a large number of customers customers that use a multi-tenant multiplexing model to offer on-demand self-service over broad network. Open source cloud computing platforms are, similar to trusted computing, a fairly recent technology in active development. The issue of trust in public cloud environments is addressed by examining the state of the art within cloud computing security and subsequently addressing the issues of establishing trust in the launch of a generic virtual machine in a public cloud environment. As a result, the thesis proposes a trusted launch protocol that allows CS clients to verify and ensure the integrity of the VM instance at launch time, as well as the integrity of the host where the VM instance is launched. The protocol relies on the use of Trusted Platform Module (TPM) for key generation and data protection. The TPM also plays an essential part in the integrity attestation of the VM instance host. Along with a theoretical, platform-agnostic protocol, the thesis also describes a detailed implementation design of the protocol using the OpenStack cloud computing platform. In order the verify the implementability of the proposed protocol, a prototype implementation has built using a distributed deployment of OpenStack. While the protocol covers only the trusted launch procedure using generic virtual machine images, it presents a step aimed to contribute towards the creation of a secure and trusted public cloud computing environment