Patent ID: 6971022

Claim:
A cryptographic apparatus comprising: a data reading means for reading content data and cryptographic information from a portable storage medium, the cryptographic information including information used to specify a certain part of the content data on which cryptographic processing is to be performed; a part specifying means for specifying, based on the read cryptographic information, the certain part of the read content data at least by detecting a specific data section in the read content data; and a cryptographic processing means for performing one of encryption and decryption on the certain part of the read content data, wherein a plurality of pieces of content data are each recorded as a file on the storage medium, along with cryptographic information for each of a plurality of file types; and the data reading means reads, from the storage medium, the content data of a file and the cryptographic information for a corresponding file type, the cryptographic information includes a reference instruction indicating that a data section in the content data be referred to, the part specifying means specifies the certain part by referring to the data section as indicated by the reference instruction, the cryptographic information includes bit pattern information showing a certain bit sequence; and the part specifying means detects, in the content data, bit data that matches the bit sequence shown in the bit pattern information, and uses a location of the bit data as a basis for specifying the certain part, the certain part having a fixed positional relationship to the bit data.