Patent ID: 7890773

Claim:
A storage medium conversion method for causing a user terminal to convert stored contents of a first memory comprising a first user data area and a first protected area where authentication between a host and the storage medium is required for access to the first protected area, in a manner of providing compatibility between, a first encryption system which uses the first memory for prestoring media identifier data, media unique key data generated based on the media identifier data, encrypted user key data stored in the first protected area and obtained by encrypting user key data in a decryptable manner based on the media unique key data, and first encrypted content key data stored in the first user data area and obtained by encrypting content key data in a decryptable manner based on the user key data, and the user terminal for storing first encrypted content obtained by encrypting content data in a decryptable manner based on the content key data, and a second encryption system which uses a second memory for storing, different from the first encryption system, encrypted title key data stored in a second protected area and obtained by encrypting title key data equivalent to the content key data in a decryptable manner based on the media unique key data, and second encrypted content obtained by encrypting the content data in a decryptable manner based on the title key data, the method comprising: generating the media unique key data based on the media identifier data read from the first memory; decrypting the encrypted user key data read from the first memory based on the media unique key data to obtain user key data; decrypting the first encrypted content key data read from the first memory based on the user key data to obtain content key data; encrypting the content key data in a decryptable manner based on the media unique key data, thereby obtaining second encrypted content key data equivalent to the encrypted title key data; writing the second encrypted content key data in the first memory; and writing the first encrypted content in the first memory.