Implementing a Multi-hat PDA

Abstract

This is work I did with Frank Stajano, which has come out of some of his stuff that he talked about at last year’s workshop, but I’ll give to anyone who wasn’t here last year a brief synopsis of what he was talking about.

The problem is this: you have a PDA, and this is inherently a single-user machine, that’s how it’s been designed. On your PDA you have some functions which you want to protect, so you might have your diary, and your journal, and your email on it, and you’d quite like to protect this so you put a password on your PDA, but you also have some functions which don’t need a password, so you have a calculator and games on your PDA, and you don’t really need a password for these. But because it’s a single-user machine, obviously only one person’s using it, so you have a password on the whole PDA because it’s all the same person. So if you want to use your calculator you still have to type your password in. The other effect of this is that if you want to lend the calculator to somebody else, demonstrate the nice screen you’ve got on your PDA, you have to type in your password and then you have given them access to all of it. And what we’d quite like to do is to be able to lend someone your PDA to play games on it, or use the calculator, without also giving them the ability to read your email.