Remotely Keyed CryptoGraphics – Secure Remote Display Access Using (Mostly) Untrusted Hardware

Debra L. Cook, Ricardo Baratto, Angelos D. Keromytis

Department of Computer Science, Columbia University Technical Report , CUCS-050-04, December 2004

Abstract

Software that covertly monitors a user’s actions, also known as spyware, has become a first-level security threat due to its ubiquity and the difficulty of detecting and removing it. Such software may be inadvertently installed by a user that is casually browsing the web, or may be purposely installed by an attacker, or even by the owner of a system to spy on other users of the system. This is particularly problematic in the case of utility computing, early manifestations of which are Internet cafes and thin-client computing. Traditional trusted computing approaches offer a partial solution to this by significantly increasing the size of the trusted computing base (TCB) to include the operating system and other software. We examine the problem of protecting a user accessing specific services in such an environment. We focus on secure video conferencing and remote desktop access when using any convenient, and often untrusted, terminal as two example applications. We posit that, at least for such applications, the TCB can be confined to a suitably modified graphics processing unit (GPU). Specifically, to prevent spyware on untrusted clients from accessing the user’s data, we investigate the possibility of restricting the boundary of trust required to the client’s GPU, and evaluate the possibility of moving decryption into GPUs. We discuss the applicability of GPU-based decryption in these two sample scenarios and identify the limitations of the current generation of GPUs. We propose straightforward modifications to future GPUs that will allow the realization of our architecture.

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cucs:050:04

Columbia University Department of Computer Science