In my last job (no longer working there) I signed an NDA at a client's request. Can't talk about anything related, can't even mention the client's name.
Now I want to apply for a job opening in the client's company. Could I mention in the cover letter that I did some work for them?
I only want to do this, because in my opinion it would increase drastically my chances for an interview.
 mentioning the client's name is a bit unclear, because according to the NDA I can disclose info that I knew before signing the agreement and I did know beforehand that the specific company was a client and I would work for them (but I'm not sure if I can prove it, because I got this info verbally)