Methods and computer program products for creating sketches of a document, which are compared with sketches of other documents, in order to determine the documents' degree of similarity. A sketch is a digest of information from random locations within a document. A document is divided into a set of shingles. Each shingle is converted into a set of fingerprints. A sketch is determined based on one bit fingerprints thus created. In order to create additional sketches of the document, a new set of fingerprints are created by randomization techniques.