Patent attributes
Client terminals report an easy-to-calculate identifier such as the Internet URL or a cryptographic hash of the content to a server. The server collects and counts the reported identifiers so as to obtain preliminary statistics. By aggregating these reported identifiers into the preliminary statistics, identifiers are revealed that are likely popular content. The server selects one or more identifiers from the preliminary statistics and makes these available to at least a subset of clients. The clients that obtain these one or more identifiers then access content and compute the easy-to-calculate identifiers as usual. If the computed identifier matches one of the identifiers obtained from the server, the client will additionally extract a watermarked identifier or compute a digital fingerprint of the content in question and report this to the server. The server then uses the received identifier or fingerprint to create final statistics by aggregating the preliminary statistics.
