Content Protection for Recordable Media (CPRM) Proposal

Transcription

1 Content Protection for Recordable Media (CPRM) Proposal To: Technical Committee T13 From: Jeffrey Lotspiech IBM Corporation 650 Harry Road San Jose, CA Date: 9 October 2000 Introduction With the widespread conversion of many content types (such as music, movies, etc.) to digital formats, the content owners concerns about uuthorized casual copying by end users have greatly increased. For example, the Secure Digital Music Initiative (SDMI) has defined requirements which media devices must meet to be acceptable targets for download of legitimately obtained music. CPRM (Content Protection for Recordable Media) technology was developed jointly by IBM, Intel, Matsushita, and Toshiba ( 4C ), and was designed to meet the requirements of SDMI. CPRM has been previously defined for DVD-RAM, for DVD-R, for DVD-RW, for the Secure Digital Memory Card (flash memory), and, in a pre-recorded variant, for DVD Audio. This proposal extends CPRM to portable ATA devices. This type of content protection is primarily useful in portable, removable, devices that need to interchange with different hosts or consumer electronics players/recorders. In other words, if an ATA device is captive to a particular host, it is usually appropriate for the host, not the device, to implement the copy protection environment. Thus, the CPRM feature is strictly optiol. The commands as described below may be included in a device without license obligations. However, to be useful in a copy protection environment, the commands need keys, keying material, and intellectual property requiring a license. This license is available from 4C Entity, LLC, and is administered by License Magement Intertiol, LLC, in California ( Proposed changes The following additions/modifications are proposed for the ATA/ATAPI-7 standard based on the ATA/ATAPI-7 rev 0 draft standard: 3.1 Definitions and Abbrieviations Add: CPRM: Content Protection for Recordable Media. This is a copy protection technology and licensing domain developed by IBM, Intel, Matsushita, and Toshiba. It is licensed by 4C Entity, LLC. The specification and licensing information is available at Media Key Block: In CPRM, the media key block is 1 MB of keying material which is placed on the media at manufacturing time. From then on, it must be logically read-only. Keying material is non-secret information that allows compliant hosts to calculate a cryptographic key, while preventing circumvention devices from calculating the same key. Media key blocks are generated by 4C Entity, LLC. A single media key block can be replicated on multiple devices. 1

2 SDMI: Secure Digital Music Initiative. This is an initiative started by the Recording Industry Association of America to combat the distribution of uuthorized copies of compressed music (for example, MP3s) on the Internet. SDMI defines the security requirements portable music players must meet to be allowed to download legitimately distributed music. SDMI check-in. In SDMI, there is a limitation placed on SDMI compliant hosts to allow no more than three copies of a single song to be placed on portable media at any one time. When the user wants to create a fourth copy, one of the existing copies must be securely deleted. This is called a check-in. SDMI move: In SDMI, a move allows a host to transfer ownership of a given song, together with all its authorized copies, to another host. Like SDMI check-in, move requires that the song must be securely deleted from the media. X.x CPRM feature set Support of the CPRM feature set is denoted by a bit in the IDENTIFY DEVICE response. Commands unique to the CPRM feature set use a single command code and are differentiated from one another by the value placed in the Features register. These commands are: READ CPRM STRUCTURE READ MEDIA KEY BLOCK INCREMENT MEDIA ID CPRM CHALLENGE The READ CPRM STRUCTURE command returns device status relevant to the CPRM copy protection scheme. For the most part, this status is dymic. In contrast, the READ MEDIA KEY BLOCK command returns constant information that is set at manufacturing time. This information is the keying material necessary for compliant hosts to interoperate through the device s media. (These formats are described in Content Protection for Recordable Media, Introduction and Common Cryptographic Elements Book, Release 0.93, and Content Protection for Recordable Media, Portable ATA Storage Book, Release 0.90, available at The INCREMENT MEDIA ID command is used to implement secure the SDMI check-in and SMDI move operations. The CPRM CHALLENGE command is used by compliant host applications to verify they are connected to a bofide CPRM device, and not a circumvention program masquerading as one. In clause IDENTIFY DEVICE Table 20 Word F/V 83 F n 1 = CPRM feature set supported 86 F n 1 = CPRM feature set ebled 8.12.xx Words 82-84: Features/command sets supported If bit n of word 83 is set to one, the CPRM feature set is supported. 2

3 8.12.xx Words 85-87: Feature/command sets ebled If bit n of word 86 is set to one, the CPRM feature set is ebled. The feature is ebled if the device was loaded at manufacturing time with a media key block and a key. 8.X CPRM Feature Set Individual CPRM feature set commands are identified by the value placed in the Features register. Table xx shows these Features register values. 8.X.1 READ CPRM STRUCTURE 8.X.1.1 Command code Table xx - CPRM Features register values Value Command 80h READ CPRM STRUCTURE 81h READ MEDIA KEY BLOCK 82h INCREMENT MEDIA ID 00h-7Fh CPRM CHALLENGE 83h-FFh Reserved 60h [subject to approval] with a Features register value of 80h. 8.X.1.2 Feature set CPRM feature set. Mandatory when the CPRM feature set is ebled. 8.X.1.3 Protocol PIO data-in. 8.X.1.4 Inputs The Features register shall be set to 80h. Features 80h Device/Head DEV Command 60h Device/Head - 3

4 8.X.1.5 Normal outputs Error Device/Head obs obs DEV Status BSY DRDY DF DRQ ERR DF (Device Fault) shall be cleared to zero. ERR shall be cleared to zero. 8.X.1.6 Error outputs If the device does not support this command, the device shall return command aborted. Error UNC ABRT Device/Head obs obs DEV Status BSY DRDY DF DRQ ERR Error register - ABRT shall be set to one if this command is not supported. UNC shall be set if an uncorrectable read error reading the CPRM data. DF (Device Fault) shall be set to one if a device fault has occurred. ERR shall be set to one if an Error register bit is set to one. 8.X.1.7 Prerequisites DRDY set to one. 4

5 8.X.1.8 Description The READ CPRM STRUCTURE command returns a 512 byte CPRM data structure via PIO datain transfer. The structure encodes device copy protection status defined by the CPRM copy protection system. 8.X.2 READ MEDIA KEY BLOCK 8.X.2.1 Command code 60h [subject to approval] with a Features register value of 81h. 8.X.2.2 Feature set CPRM feature set. Mandatory when the CPRM feature set is ebled. 8.X.2.3 Protocol PIO data-in. 8.X.2.4 Inputs The Features register shall be set to 81h. Features 81h MKB count MKB sector - low MKB sector - high Device/Head DEV Command 60h The number of MKB sectors to be transferred. 00h denotes 256 sectors., These two registers are treated as a 16-bit number to specify the sector within the media key block to begin the transfer from. The is the more significant byte. Device/Head - 5

6 8.X.2.5 Normal outputs Error Device/Head obs obs DEV Status BSY DRDY DF DRQ ERR DF (Device Fault) shall be cleared to zero. ERR shall be cleared to zero. 8.X.2.6 Error outputs If the device does not support this command, the device shall return command aborted. Error UNC IDNF ABRT MKB sector low MKB sector high Device/Head obs obs DEV Status BSY DRDY DF DRQ ERR Error register - ABRT shall be set to one if this command is not supported. IDNF shall be set if the requested range is out of bounds for the MKB UNC shall be set if an uncorrectable read error. DF (Device Fault) shall be set to one if a device fault has occurred. ERR shall be set to one if an Error register bit is set to one., These registers are treated as a 16-bit number specifying the failing sector number, in the case that UNC is set. Otherwise, the values are undetermined. 8.X.2.7 Prerequisites DRDY set to one. 6

7 8.X.2.8 Description The READ MEDIA KEY BLOCK command returns a Nx512 byte media key block data bytes, beginning at the specified media key block sector, via PIO data-in transfer. ( N comes from the register.) The media key block contains keying material defined by the CPRM copy protection system. 8.X.3 INCREMENT MEDIA ID 8.X.3.1 Command code 60h [subject to approval] with a Features register value of 82h. 8.X.3.2 Feature set CPRM feature set. Mandatory when CPRM feature set is ebled. 8.X.3.3 Protocol Non-data. 8.X.3.4 Inputs The Features register shall be set to 82h. Features 82h 6Eh B2h Device/Head DEV Command 60h Device/Head - Shall be set to 6Eh. Shall be set to B2h. 8.X.3.5 Normal outputs Error Device/Head obs obs DEV Status BSY DRDY DF DRQ ERR 7

8 DF (Device Fault) shall be cleared to zero. ERR shall be cleared to zero. 8.X.3.6 Error outputs If the device does not support this command, or if the is not 6Eh, or if the Cylinder High is not B2h, the device shall return command aborted. Error UNC ABRT Device/Head obs obs DEV Status BSY DRDY DF DRQ ERR Error register - ABRT shall be set to one if this command is not supported, or if is not 6Eh, or if is not B2h. UNC shall be set to one if there was a uncorrected error while incrementing the media ID. DF (Device Fault) shall be set to one if a device fault has occurred. ERR shall be set to one if an Error register bit is set to one. 8.X.3.7 Prerequisites DRDY set to one. 8.X.3.8 Description The INCREMENT MEDIA ID command is used in SDMI check-in and SDMI move operations as part of a secure file delete operation. 8.X.4 CPRM CHALLENGE 8.X.4.1 Command code 60h [subject to approval] with a Features register values 00h-7Fh. (The low order seven bits of the Features register are actually used as data in the command.) 8

9 8.X.4.2 Feature set CPRM feature set. This command is mandatory if the CPRM feature set is ebled. 8.X.4.3 Protocol Non-data. 8.X.4.4 Inputs The Features register bit 7 shall be set to zero. Features 0 c4 c3 c2 c1 c0 Device/Head DEV Command 60h Device/Head - Features,,,, Are treated as a 39-bit number concateting c4 to c3 to c2 to c1 to c0. 8.X.4.5 Normal outputs Error Device/Head obs obs DEV Status BSY DRDY DF DRQ ERR DF (Device Fault) shall be cleared to zero. ERR shall be cleared to zero. 8.X.4.6 Error outputs If the device does not support this command or if the device is not ebled, the device shall return command aborted. 9

10 Error UNC ABRT Device/Head obs obs DEV Status BSY DRDY DF DRQ ERR Error register - ABRT shall be set to one if this command is not supported or the device does not have a media unique key. UNC shall be set to one if there was a uncorrected error while storing the Challenge Response. DF (Device Fault) shall be set to one if a device fault has occurred. ERR shall be set to one if an Error register bit is set to one. 8.X.4.7 Prerequisites DRDY set to one. 8.X.4.8 Description The CPRM CHALLENGE command is used in conjunction with the READ CPRM STRUCTURE command to allow the host to verify that it is connected to a valid CPRM device, and not a circumvention program masquerading as one. 10