The presently claimed invention generally relates to deriving and/or utilizing content signatures (e.g., so-called “fingerprints”). One claim recites a method comprising: obtaining a sequence of content identifiers, the sequence of content identifiers corresponding to one or more segments of a media signal; and utilizing at least a processor or electronic processing circuitry, carrying out a convolution operation based on the sequence of content identifiers and content signatures housed or stored in a database to identify the media signal. Of course, other claims and combination are provided as well.