in General, Tech

Reverse engineering Flickr

As part of a puzzle for the Last Call Poker game I mentioned before, I managed to look up and trace back a Flickr picture to its poster’s account. I didn’t run into a guide on how to do it, despite searching for one. So now I set out to create what I wish I’d found.

Flickr photos can be posted around the web with URLs in this format:

Looking at the numbers, there’s no obvious way to tell whose account it came from. For the puzzle, a picture with a URL in this format appeared on the game’s website. Our goal was to discover the full name of the character who took the photo, which I assumed was located in his Flickr account page.

After researching Flickr’s URL structure a bit, I discovered that the the first portion of the last chunk of the address (in this case ‘31607655’) is a unique ID number for the photo.

Flickr themselves provide a method to look up the owner of the ID in the Flickr API. It isn’t well publicized, but is located here.

Plug in ‘31607655’, and it returns an XML file full of all kinds of info on the photo. The account, tags, description, notes, etc. From there its just a matter of copying and pasting the account holder’s URL.

Simple in retrospect, but it took a bit of digging to uncover. As an added lesson, I now know not to assume my flickr pictures are anonymous just because I post the scrambled URL.