How to create a custom permission in SharePoint 2010?

Hi All,

One of our client wants to have custom permission to see encrypted document items  on a site collection. Only if the user is having this permission he should be able to view encrypted document items.

Is it possible in SharePoint 2010 to create a custom permission such as "View Encrypted Items" which I should be able to include in a custom permission level?

Thanks,

Rahul Babar

ASP.NET, C# 4.0, Sharepoint 2007/2010, Infopath 2007/2010 Developer