YSK dogs usually don't sniff drugs because they don't know what is expected from them. Instead, they act on body cues from the handler, which is also looking for body cues from the suspect.

In other words, the cop is looking at you for when you're nervous, and then telling the dog to look further on that place.

If you stay still and relaxed, they won't be able to tell.

(Unless they know you're carrying, then it's just a matter of time and effort)