Method and apparatus for processing data sequences for the purpose of data integrity assessment, data ownership demonstration and data authentication. An input data sequence is processed to extract what could be called naturally occurring digital watermarks. More appropriately, these naturally occurring digital watermarks are referred to herein as fileprints. Fileprints are data sequences that have been extracted from the input data sequence in a repeatable manner, and are with high probability unique to that input. In this sense, a fileprint can be used to identify which data sequence it came from, just as a human fingerprint can identify a particular person to which it belongs. Because the fileprints have not been embedded, they are not actually digital watermarks. However, fileprints can be used in a like fashion to digital watermarks for information protection.