My worry about this is that it is yet another place for the implementation quality of your browser to be largely responsible for the security of your data. While I think Microsoft does a fine job of security R&D, the tend to massively fail when it comes time to actually deliver.
At a fundamental level, simplicity of mechanism has to be part of any secure system. Every major MS stack (Windows kernel+core API, IE+ActiveX+JScript, Office+VBA) is just too huge, and has too many little back doors around the security infrastructure built in for performance and backwards-compatibility.
Now, if they truly willing to commit to using a substrate like Singularity for their trusted computing base, we can talk about security.
The better way to handle this, of course, is separate browser runtimes for separate applications, ala Prism/XULRunner. Each desktop app should have a whitelist of hosts it's allowed to access, and sharing can be accomplished via normal local system channels.
At a fundamental level, simplicity of mechanism has to be part of any secure system. Every major MS stack (Windows kernel+core API, IE+ActiveX+JScript, Office+VBA) is just too huge, and has too many little back doors around the security infrastructure built in for performance and backwards-compatibility.
Now, if they truly willing to commit to using a substrate like Singularity for their trusted computing base, we can talk about security.
The better way to handle this, of course, is separate browser runtimes for separate applications, ala Prism/XULRunner. Each desktop app should have a whitelist of hosts it's allowed to access, and sharing can be accomplished via normal local system channels.