An information processing apparatus, an information recording medium, an information processing method, and a computer program are provided.In an information recording medium storing many pieces of content, a configuration that allows use management on segmented content basis is provided. A plurality of content management units corresponding to title, index and other information are set by partitioning stored content in an information recording medium. Different unit keys that are encryption keys are allocated to different content management units. At least the content real data included in each content management unit is encrypted by use of the unit key and the encrypted data is stored. In content reproduction, units are identified and decryption is executed by use of a unit key corresponding to each unit for reproduction. In an information recording medium storing many pieces of content for example, each of segmented pieces of content may be managed.