If a police officer does not have probably cause to suspect that I have committed, or am engaged in committing, a crime, who I am is none of his damn beeswax.
If a police officer does have probable cause to suspect that I have committed, or am engaged in committing, a crime, I am under no obligation to assist in my own prosecution, including but not limited to revealing my identity to make it easier for him to investigate me.
I can see reasons to voluntarily produce "identification papers" for other purposes, of course, but those other people aren't government agents of any sort.
