When hackers break into the databases of the great and good—like Adobe—they're often left with an encrypted password and an unencrypted password hint. In other words, a giant, modern version of a crossword puzzle.

As Randall Munroe points out, the hackers are essentially presented with a set of clues, the answers to which are of a known character length. Screw the NYT cryptic; this is a real challenge. [XKCD]