Derived SMEK TISCI Description¶
Note
This feature is only supported in j721S2 and j784S4 devices
This chapter provides information on System Firmware API for Derived Symmetric Encryption key (dsmek) management. The available API are listed below.
| TISCI Message ID | Message Name | Available in GP | Available in HS-FS |
|---|---|---|---|
| 0x9036 | TISCI_MSG_SA2UL_GET_DSMEK | Yes* | Yes* |
| 0x9037 | TISCI_MSG_SA2UL_SET_DSMEK | Yes* | Yes* |
| 0x9038 | TISCI_MSG_SA2UL_RELEASE_DSMEK | Yes* | Yes* |
Note
On GP and HS-FS devices, DSMEK APIs return unconditional success but do not actually involve any step to derive or program the dsmek values
API Description¶
TISCI Message ID¶
TISCI_MSG_SA2UL_SET_DSMEK (0x9037U)
Message to derive a SMEK and set SA2UL DKEK register
struct tisci_msg_sa2ul_set_dsmek_req
TISCI Request for setting DSMEK in SA2UL registers
| Parameter | Type | Description |
|---|---|---|
| hdr | struct tisci_header | Generic TISCI message header. |
| sa2ul_instance | u8 | SA2UL instance number - set to 0 |
| kdf_label_len | u8 | Length of “Label” input to KDF |
| kdf_context_len | u8 | Length of “Context” input to KDF |
| kdf_label_and_context | u8 | ”Label” and “Context” bytes are stored in this array one after another. Maximum length of this field is KDF_LABEL_AND_CONTEXT_LEN_MAX |
struct tisci_msg_sa2ul_set_dsmek_resp
TISCI Response for setting DSMEK in SA2UL registers
| Parameter | Type | Description |
|---|---|---|
| hdr | struct tisci_header | Generic TISCI message header. |
KDF_LABEL_AND_CONTEXT_LEN_MAX 41U
See API Notes below.
TISCI Message ID¶
TISCI_MSG_SA2UL_RELEASE_DSMEK (0x9038U)
Message to erase the DKEK register
struct tisci_msg_sa2ul_release_dsmek_req
TISCI Request for releasing DSMEK
| Parameter | Type | Description |
|---|---|---|
| hdr | struct tisci_header | Generic TISCI message header. |
| sa2ul_instance | u8 | SA2UL instance number - set to 0 |
struct tisci_msg_sa2ul_release_dsmek_resp
TISCI Response for Releasing DSMEK
| Parameter | Type | Description |
|---|---|---|
| hdr | struct tisci_header | Generic TISCI message header. |
See API Notes below.
TISCI Message ID¶
TISCI_MSG_SA2UL_GET_DSMEK (0x9036U)
Message to derive a SMEK and return it via TISCI
SA2UL_DSMEK_KEY_LEN (32U)
struct tisci_msg_sa2ul_get_dsmek_req
TISCI Request for getting DSMEK via TISCI
| Parameter | Type | Description |
|---|---|---|
| hdr | struct tisci_header | Generic TISCI message header. |
| sa2ul_instance | u8 | SA2UL instance number - set to 0 |
| kdf_label_len | u8 | Length of “Label” input to KDF |
| kdf_context_len | u8 | Length of “Context” input to KDF |
| kdf_label_and_context | u8 | ”Label” and “Context” bytes are stored in this array one after another. Maximum length of this field is KDF_LABEL_AND_CONTEXT_LEN_MAX |
struct tisci_msg_sa2ul_get_dsmek_resp
TISCI Response for requesting DSMEK
| Parameter | Type | Description |
|---|---|---|
| hdr | struct tisci_header | Generic TISCI message header. |
| dsmek | u8 | Array containing Derived KEK. Length is 32 bytes |
See API Notes below.
API Notes¶
- The total length of the Label and Context fields below is limited by the size of the TISCI messages(see Secure Messaging Header) to 41 bytes.
- System Firmware only support
sa2ul_instancevalue of 0 in the API below.