Can htcp and cache digest work together?

["John Lui" <johnluicn@xxxxxxxxx>]

Hi,
   I read the book named "Squid: The Definitive Guide" writed by  O'Reilly.
   In the Chapter 10, it mean icp can work with cache digest.
   i have these questions:
  1, Can htcp work with cache digest?
  2, How I can checked the cache digest is be used?
  3, What is better to choice,ICP or HTCP?


thks
John Lui