Occasionally in a novel, you have a point where there is dialogue, but only parts of it matter. You usually see this where the hero conveniently catches only the words he needs to hear:
He could only make out a few words: "Enemy... coming... keep... daughter... safe."
Using ellipsis like that is usually how dialogue is written when only some of the words matter. At least that's how I've seen it written, and it seems to work for my own uses.
However, I now have a similar problem, though it is much more complex. In my sci-fi-ish novel, evil robots have taken over the world and imprisoned humanity (extreme over-simplification; the novel is vastly better than that). The computers of the robots are highly advanced, and the prisoners are kept under constant surveillance.
Due to these conditions, the prisoners have had to develop a code even the smartest computer can't break - the code it can't find. During a seemingly-normal conversation, they will emphasize certain words, which together make up the line they are saying. For instance, during a handshake, they might squeeze extra hard on "meet", "behind", and "closet". All the surveillance would see was perhaps an overlong greeting. This code can be initiated with anything - taps inside the palm, touching the shoulder; the point is, only certain words matter in a long string of dialogue.
This is of course different from the above example, so is there a better way I could write it?
Should I include the whole dialogue, or should I show only the relevant words? So for example:
Laura listened to every word he squeezed her hand on, and slowly a message began to appear: "You have to get to the counter behind the yellow stripe. They served Jake and me there." A pause. "They're great at cooking, I swear the meals have been looking almost like real meat for a while now. What do you think?"
Laura listened to every word he squeezed her hand on, and slowly a message began to appear: "Get... behind... me. They're... looking... for... you."
Which method is best?