To prevent efficiency from being lowered by enabling the encryption control of a sector unit in a data format in which the data of different systems are merged together.
The leading bits 32 (a1) and bits 33 (a2) of one sector are used for encryption control. The 2 bits and the remaining 30 bits are used as IV. Data after 64 bits are decoded. According to an MPEG2 system, control codes (a1, a2) are arranged next to the leading 32 bits (pack start code), and an SCR is arranged thereafter. The IV is constituted of 30 bits of SCR and the size of user data is 2,016 bytes. In a general data format, the leading 32 bits are used as a reserved or system header, 2-bit control codes a1, a2 are arranged next, and the remaining 30 bits are random numbers. The control codes and the random numbers are IV. The size of the user data becomes 2,040 bytes.
Takuma Sugiura
Koichi Mori