NDA prevents you from giving specifics about project.
The technical knowledge you gained can be proved in the interview.This is were things like your participation on forums and Q and A sites during the time of your involvement comes in handy.
There are some NDA/contract agreement which explicitly prevent you from utilizing the technology or seeking work in similar /competing for a duration of time. though this might be more common in employment contracts. it would not be surprising if these type of clauses are present in NDA's.
concentrate on proving yourself in the interview. If you really have the stuff.it really should not matter.
Also remember, you can always develop applications of your own specifically to showcase your talent. This you can do it on your own time and/or after your involvement with an NDA project.