Custom UI element and client side question

Hi, I'm currently developing a web application and evaluating Vaadin.
The framework looks great, I am working on convincing the development manager to pick it.

I have several questions:
1. Maybe I haven't looked around too well, but say I am using a Table (Grid) and I want some of the elements to have lines crossing the whole line and extending outside
(something I guess will need a canvas-like feature) is it possible? Can I add a table on top of a canvas so I can "paint" whatever-I-want on the table?

2. We will need to bring encrypted data from the server to the client, and the user will be providing a key to decrypt it, which will result the actual data needed to be rendered.
How can it be done in Vaadin if Vaadin relies on the server so much.

Thanks!
Chen