Lyric discussion by solitary walker 

Cover art for Codes and Keys lyrics by Death Cab for Cutie

I wonder if the "codes and keys" reference has to do with the utilization of technology as a way of "protecting" oneself "from the pangs of jealousy." Both Ben and Zooey are pretty active on twitter, and perhaps he was drawing inspiration from the evolving world of social networking - you can throw up walls and pretend to be someone that you're not, putting up the front that everything is okay when it's actually the exact opposite. The album art also has a "hashtag" (pound sign) on the cover, so that might also tie into the theme as well.