TNC Architecture for Interoperability TCG Copyright
Specification Version 1.5
Revision 3 Published Page 9 of 45
TCG PUBLISHED
2 Introduction
The TNC architecture focuses on interoperability of network access control solutions and on the
use of trusted computing as the basis for enhancing security of those solutions. Integrity
measurements are used as evidence of the security posture of the endpoint so access control
solutions can evaluate the endpoint's suitability for being given access to the network.
The purpose of the current document is to define the Trusted Network Connect (TNC)
architecture for interoperable network access control and authorization. The TNC architecture will
leverage and integrate with existing network access control mechanisms such as 802.1X [19] or
others. The TNC specifications will also define interoperability interfaces to allow for the
exchange of new types of attributes in the context of network access control solutions. Those
attributes will include endpoint compliance information, software state attestation, as well as
information pertaining to the Platform-Authentication exchange [2].
Note that in the remainder of this document, the term “Platform-Authentication” carries the
specific TCG meaning of performing verification of the integrity status of a platform using the
features of Trusted Platforms [1]. These features represent the core functionality of trusted
computing as defined and specified by the TCG.
The term “Platform-Authentication” as used in
the context of TNC pertains to two related aspects of authentication. The first aspect is the proof
of identity of the platform (or “Platform Credential Authentication”), while the second aspect is the
integrity verification (or “Integrity Check Handshake”) of the platform. In the specific context of the
TCG, proving the identity of a platform is performed using any non-migratable key (e.g., an AIK).
Since there are an unlimited number of non-migratable keys associated with a TPM there are an
unlimited number of identities that can be deployed to effect privacy of the user on the platform.
Note that claimed identity in a platform may or may not be related to the user or any actions
performed by the user (see [3]).
In the remainder of this document, the term “Platform-Authentication” therefore should generally
be understood as consisting of both aspects, namely establishing proof of identity (e.g. via AIK-
certificates) and platform integrity verification.
2.1 Endpoint Integrity: Background
The growth of the Internet IP infrastructure in the last few years has introduced new technologies
and new security challenges. One of these security challenges concerns the increasing need for
machine-to-machine identification and authentication, and network access authorization in
addition to the usual user authentication. Machine level Platform-Authentication is crucial for the
security and authorization of network-access requests at both layer-2 and layer-3. Furthermore,
due to the large number of attacks from malware (worms, viruses, spyware) and alike against
higher layers of the network stack, network operators need the ability to evaluate the security
posture (defensive measures) against such threats prior to allowing access.
The problem of endpoint integrity concerns the trustworthiness of two communicating endpoints
(e.g. Client and Server) from the perspective of the integrity conditions of the two endpoints,
including their identities. By the term integrity we mean the relative purity of the endpoints from
software (and hardware) that are considered harmful to the endpoint itself and others with whom
it interacts. This problem of harmful software is best exemplified by the growing number of virus
and Trojan attacks on corporate networks. Many employees today connect their mobile devices
(e.g. laptops, PDAs) at home to the open Internet, often resulting in malware being inadvertently
downloaded onto the device. When connected to the corporate network, the device becomes a
distributor of the malware to other devices on the Enterprise network.
Since the term Platform Authentication carries a distinct TCG meaning, the two words are
hyphenated (“platform-authentication”) in the current document to differentiate it from the more
general meaning of authentication/authorization of a general computing platform.