An information processing system includes: a data processing unit that executes verification processing for a content recorded in a disk and reproduces the disk-recorded content under a condition that the verification succeeds, wherein the data processing unit randomly selects hash units, which are objects of collation, from among a plurality of hash units formed with component data items of the content, reads the selected hash units sequentially from the disk, calculates hash values, and collates the calculated hash values with collation hash values; and the data processing unit executes reading sequence determination processing so as to determine a reading sequence in which the selected hash units are sorted according to recording positions in a disk, and reads the selected hash units according to the determined reading sequence.