Marcel Selhorst

TCG inside?: a note on TPM specification compliance

The Trusted Computing Group (TCG) has addressed a new generation of computing platforms employing both supplemental hardware and software with the primary goal to improve the security and the trustworthiness of future IT systems. The core component of the TCG proposal is the Trusted Platform Module (TPM) providing certain cryptographic functions. Many vendors currently equip their platforms with a TPM claiming to be TCG compliant. However, there is no feasible way for application developers and users of TPM-enabled systems to verify this compliance. In practice, manufacturers may exploit the flexibility that the specification itself provides, or they may deviate from it by inappropriate design that might lead to security vulnerabilities. Hence, it is crucial to have an independent means for testing the compliance as well as analyzing the security of different TPMs. In this paper, we aim at making the first steps towards fulfilling this requirement: We have developed a test strategy as well as a prototype test suite for TPM compliance testing. Although our test does not cover the complete TCG specification, our test results show that many TPM implementations do not meet the TCG specification and have bugs. Moreover, we discuss that non-compliance may have crucial impact on security, and point out the corresponding security problems in case of a widespread TPM.

Realizing property-based attestation and sealing with commonly available hard- and software

The authenticated boot process introduced by the Trusted Computing Group (TCG) uses binary measurements, i.e., hashes of executables, to give an indication of which software configuration runs on a given computing platform. As the binary measurements change with any software update, sealed data becomes unavailable, too. To solve this and other problems regarding binary measurements, the concept ofproperty-based attestation has been introduced. In this paper we show how to realize both property-based attestation and property-based sealing using existing TCG-enabled hard- and software. The main idea is that an enhanced boot loader translates between binary measurements and properties, allowing to attest properties of unmodified operating systems loaded. Moreover, applications running on top of this operating system can use existing mechanisms, e.g., an existing Trusted Software Stack (TSS) implementation, to seal data to properties instead of binary hash values One cornerstone of our proposal is the ability to also revoke the translation of certain binary measurements into properties in case of identified security problems. Our proposal is ideally suited for enterprise environments having a centralized IT-management infrastructure and scales well with the number of participating clients.

Security Versus Usability – User-Friendly Qualified Signatures Based on German ID Cards

The new German ID card introduced in 2010 and the electronic residence permit introduced in 2011 are two state-of-the-art ID documents with innovative electronic functions for people living in Germany. Citizens can use both documents for official functions as well as for user identification on the web (also called eID function or online ID function) and for generating qualified electronic signatures (also called eSign function or online signature function).

Enhancing Security of Computing Platforms with TC-Technology

We present an open security platform based on the specification of the Trusted Computing Group (TCG). The features provided by the proposed platform can be used to solve many existing security problems. The platform’s main components are a conventional operating system, a security software layer (PERSEUS), and the hardware offered by the TCG. Exploiting the TCG functionalities, our security platform offers a variety of secure (trusted) services, e.g., secure booting, secure user interface, trusted GUI, and a trusted viewer, which are not offered by commonly used computing platforms. Together these services allow the implementation of security-critical applications, such as those generating digital signatures or enforcing a certain policy, while providing backward-compatibility to an existing operating system.