Frankly, when you tell a room full of people about something it's practically guaranteed to leak. The exceptions seem to be (a) secrets nobody cares about ("We're rewriting our ductwork design software!") and things that involve government secrets (and that doesn't always work).

I had a couple of housemates who were in the US submarine service. They never talked about what they did, even 20 years retired, and were very upset when the book Blind Man's Bluff was published.