Secure Code Update for Embedded Devices via Proofs of Secure Erasure

Abstract. Remote attestation is the process of verifying internal state of a remote embedded device. It is an important component of many security protocols and applications. Although previously proposed re-mote attestation techniques assisted by specialized secure hardware are effective, they not yet viable for low-cost embedded devices. One no-table alternative is software-based attestation, that is both less costly and more efficient. However, recent results identified weaknesses in some proposed software-based methods, thus showing that security of remote software attestation remains a challenge. Inspired by these developments, this paper explores an approach that relies neither on secure hardware nor on tight timing constraints typi-cal of software-based technqiques. By taking advantage of the bounded memory/storage model of low-cost embedded devices and assuming a small amount of read-only memory (ROM), our approach involves a new primitive – Proofs of Secure Erasure (PoSE-s). We also show that, even though it is effective and provably secure, PoSE-based attestation is not cheap. However, it is particularly well-suited and practical for two other related tasks: secure code update and secure memory/storage erasure. We consider several flavors of PoSE-based protocols and demonstrate their feasibility in the context of existing commodity embedded devices.

The Effect of Identifying Vulnerabilities and Patching Software on the Utility of Network Intrusion Detection

Vulnerability scanning and installing software patches for known vulnerabilities greatly affects the utility of network-based intrusion detection systems that use signatures to detect system compromises. A detailed timeline analysis of important remote-to-local vulnerabilities demonstrates (1) Vulnerabilities in widely-used server software are discovered infrequently (at most 6 times a year) and (2) Software patches to prevent vulnerabilities from being exploited are available before or simultaneously with signatures. Signature-based intrusion detection systems will thus never detect successful system compromises on small secure sites when patches are installed as soon as they are available

Security vulnerabilities in software systems: A quantitative perspective

Abstract. Security and reliability are important attributes of complex software systems. It is now common to use quantitative methods for evaluating and managing reliability. In this work we examine the feasibility of quantitatively characterizing some aspects of security.In particular, we investigate if it is possible to predict the number of vulnerabilities that can potentially be identified in a future release of a software system. We use several major operating systems as representatives of complex software systems. The data on vulnerabilities discovered in some of the popular operating systems is analyzed. We examine this data to determine if the density of vulnerabilities in a program is a useful measure. We try to identify what fraction of software defects are security related, i.e., are vulnerabilities. We examine the dynamics of vulnerability discovery hypothesizing that it may lead us to an estimate of the magnitude of the undiscovered vulnerabilities still present in the system. We consider the vulnerability-discovery rate to see if models can be developed to project future trends. Finally, we use the data for both commercial and open-source systems to determine whether the key observations are generally applicable. Our results indicate that the values of vulnerability densities fall within a range of values, just like the commonly used measure of defect density for general defects. Our examination also reveals that vulnerability discovery may be influenced by several factors including sharing of codes between successive versions of a software system.