Cloud Terminal: Secure Access to Sensitive Applications from Untrusted Systems

Current PC- and web-based applications provide insufficient security for the information they access, because vulnerabilities anywhere in a large client software stack can compromise confidentiality and integrity. We propose a new architecture for secure applications, Cloud Terminal, in which the only software running on the end host is a lightweight secure thin terminal, and most application logic is in a remote cloud rendering engine. The secure thin terminal has a very small TCB (23 KLOC) and no dependence on the untrusted OS, so it can be easily checked and remotely attested to. The terminal is also general-purpose: it simply supplies a secure display and input path to remote software. The cloud rendering engine runs an off-the-shelf application in a restricted VM hosted by the provider, but resource sharing between VMs lets one server support hundreds of users. We implement a secure thin terminal that runs on standard PC hardware and provides a responsive interface to applications like banking, email, and document editing. We also show that our cloud rendering engine can provide secure online banking for 5–10 cents per user per month.