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What Is a Trusted Platform?

A Trusted Platform is a computing platform that has a trusted component, probably in the form of built-in hardware, which it uses to create a foundation of trust for software processes. The computing platforms listed in the TCPA specification are one such type of Trusted Platform. Although different types of Trusted Platforms could be built, we concentrate in particular on the (version 1.1) instantiation specified by the TCPA industry standard.

Converting a platform into a Trusted Platform involves extra hardware roughly equivalent to that of a smart card, with some enhancements.

At the time of writing, secure operating systems use different levels of hardware privilege to logically isolate programs and provide robust platform operation, including security functions.

Converting a platform into a Trusted Platform requires that TCPA roots of trust be embedded in the platform, enabling the platform to be trusted by both local and remote users. In particular, cost-effective security hardware acts as a root of trust in Trusted Platforms. This security hardware contains those security functions that must be trusted. The hardware is a root of trust in a process that measures the platform's software environment. In fact, it could also measure the hardware environment, but the software environment is important because the primary issue is knowing what the computing engine is doing. If the software environment is found to be trustworthy enough for some particular purpose, all other security functions—and ordinary software—can operate as normal processes. These roots of trust are core TCPA capabilities.

Adding the full set of TCPA capabilities to a normal, non-secure platform gives it some properties similar to that of a secure computer with roots of trust. The resultant platform has robust security capabilities and robust methods of determining the state of the platform. Among other things, it can prevent access to sensitive data (or secrets) if the platform is not operating as expected. Adding TCPA technology to a platform doesn't change other aspects of platform robustness, so a non-secure platform that's enhanced in the way described above is not a conventional secure computer and probably not as robust as a secure platform that's enhanced in the same way. Nevertheless, we believe that the architectural changes proposed in the TCPA specification are the cheapest way to enhance security in an ordinary, non-secure computing platform. The architectural cost of converting a secure platform into a Trusted Platform is even less, because it requires fewer TCPA functions.

Any type of computing platform—for example, a PC, server, personal digital assistant (PDA), printer, or mobile phone)—can be a Trusted Platform. A Trusted Platform is particularly useful as a connected and/or physically mobile platform, because the need for stronger trust and confidence in computer platforms increases with connectivity and physical mobility. In addition to threats associated with connecting to the Internet, such as the downloading of viruses, physical mobility increases the risk of unauthorized access to the platform—including actual theft. Trusted Platform technology provides mechanisms that are useful in both circumstances.

The first Trusted Platforms containing the new hardware will be desktop or laptop PCs. They'll protect secrets—keys that encrypt files and messages, keys that sign data, and authorization data—using access codes, binding of secrets to a particular physical platform, digital signing using those secrets, plus mechanisms and protocols to ensure that a platform has loaded its software properly. Later, Trusted Platforms will provide more advanced features such as protection of secrets depending on the software that's loaded (for instance, preventing a secret from being accessed if unknown software has been loaded on the platform, such as hacker scripts) and attestation identities for e-services. The technology is certain to evolve in the coming years.

Trusted Platforms are an unfamiliar concept, even to security specialists. However, since the release of TCPA specification v1.0 in February 2001 and its backing by IT organizations and companies, Trusted Platforms are set to become widely available. The adoption of Trusted Platforms is an important step toward improving confidence in conducting business over the Internet and broadening the scope of e-services. TCPA technology allows existing applications to benefit from enhanced security and encourages the development of new applications or services that require higher security levels than are presently available. Applications and services that would benefit from using Trusted Platforms include electronic cash, email, hot-desking (allowing mobile users to share a pool of computers), platform management, single sign-on (enabling the user to authenticate himself or herself just once when using different applications during the same work session), virtual private networks, Web access, and digital content delivery. The functions of the security hardware are relatively benign as far as product export/import regulations are concerned, and all contentious security functions are implemented as security software and can be changed as required for individual markets.

Another important Trusted Platform property is that the functions of the security hardware operate on small amounts of data, permitting acceptable levels of performance even though the hardware is low cost. In contrast, the normal platform processor is used by a Trusted Platform's security software to manipulate large amounts of data and, as a result, to take advantage of the excellent price-to-performance ratio of normal computer platforms.

Determining the integrity of a platform—trusting a platform—is a critical feature of a Trusted Platform. Security mechanisms (processes or features) are used to provide the information needed to deduce the level of trust in a platform. Only the user who wants to use the platform can make the decision whether to trust the platform. The decision will change according to the intended use of the platform, even if the platform remains unchanged. The user needs to rely on statements by trusted individuals or organizations about the proper behavior of a platform. This aspect ultimately differentiates a Trusted Platform from a conventional secure computer.

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