Tagging the Turtle: Local Attestation for Kiosk Computing

Abstract

Public kiosk computers are especially exposed and the software running on them usually cannot be assumed to be unaltered and secure. The Trusted Platform Module (TPM) as a root of trust in an otherwise untrusted computer allows a machine to report the integrity and the configuration of a platform to a remote host on the Internet. A natural usage scenario is to perform such an Attestation prior to handling sensitive or private data on a public terminal.Two challenges arise. First, the human user needs to reach her trust decision on the basis of the TPM’s cryptographic protocols. She cannot trust the public machine to display authentic results. Second, there is currently no way for the user to establish that the particular machine faced actually contains the TPM that performs the Attestation.In this paper we demonstrate an Attestation token architecture which is based on a commodity smart phone and more efficient and flexible than previous proposals. Further, we propose to add a low-cost Near Field Communication (NFC) compatible autonomic interface to the TPM, providing a direct channel for proof of the TPM’s identity and local proximity to the Attestation token.