1. An image reading apparatus comprising: a reading section for reading images recorded on sheets; and a controller capable of performing operations of: extracting a plurality of patterns from a first image on a sheet read using said reading section; extracting a combination information regarding a combination of a plurality of the patterns from a second image on a different sheet from the sheet read using said reading section, judging whether the combination of the extracted a plurality of patterns of the first image coincides with the combination designated using the extracted combination information of the second image; and carrying out predetermined processing according to the result of the judgment.