System Firmware Authentication and Decryption Requests


This document is only applicable to HS devices.


System Firmware provides authentication and decryption services for various binary data types using customer root-of-trust keys programmed into the device efuses.

The TISCI_MSG_PROC_AUTH_BOOT API is used to authenticate and (optionally) decrypt a binary image according to the needs for the secure application. This API serves a dual purpose in the definition from System Firmware:

Authenticated Processor Boot

Authentication of binary images which are to be executed in a secure boot flow, with chain of trust guaranteed by System Firmware.

Generalized Authentication

Authenticate a generic binary image which contains user IP or data which must be guaranteed authenticity by System Firmware.

Supported Signing Methods

System Firmware supports signature verification using RSASSA-PKCS1-v1_5 as described in [1]. Currently only RSA-4K keys are supported.

Certificate Extensions

The below sections describe which extensions are mandatory and optional in order to make authentication requests from System Firmware

See the description for the Applicability of certificate extensions to image types binary type in the System Firmware X.509 extension reference for full details on mandatory and optional extensions for all authenticated binary types.

Mandatory Extensions

At a minimum, all authenticated data must include System Firmware Image Integrity Extension and System Firmware Load Extension to provide integrity details on the data payload.

  • All integrity checking is performed by checking the SHA2-512 hash of the data payload and no other format is currently supported.
  • The load extension indicates whether the data shall be validated in-place or copied to another destination.

The System Firmware Software Revision Extension is mandatory with suggested minimum value of 1. After initial certificate parsing and validation, currently no additional actions are taken by the presence of this extension. Its use is reserved for future definition TBD.

Optional Extensions


The System Firmware Encryption Extension optionally allows for AES-256-CBC decryption of the data payload. This is applicable to any payload type which requires encryption protection, including processor boot or generic data binaries.

Processor Configuration

System Firmware Boot Extension provides means to configure the processor options defined in Generic Processor Flags. This guarantees authenticated configuration of the processor’s boot vector and other processor-specific parameters critical for the secure boot operation.

Omission of this extension effectively renders the call to TISCI_MSG_PROC_AUTH_BOOT to the generalized authentication request mentioned earlier in this document.

Authentication Sequence

The following diagram shows the sequence which System Firmware applies when authenticating a binary image.


The sequence can be described in the following steps upon call of the TISCI_MSG_PROC_AUTH_BOOT

  1. Verify integrity of the public key in certificate, comparing its hash against the hash programmed into the OTP efuse. Values must agree.
  2. Authentication: Authentication of digital signature in the certificate. Must agree
  3. Image Data Integrity: Hash of data payload is taken while loaded into the address specified in the load extension. Hash of payload must match integrity value.
  4. IP Confidentiality: Executable/secret data is optionally decrypted
  5. Authenticated Decryption: Decrypted results checked for correctness using the magic number in the extension

Only if the above steps are valid will the API continue taking action as requested:

  • Generic authentication: API will return ACK if above checks are successful
  • Processor boot authentication: System Firmware will now attempt to apply the processor configuration found in the extension, using the same rules as TISCI_MSG_PROC_SET_CONFIG - Set Processor Configuration. API will return ACK if successful.


  1. RFC-8017 | PKCS #1: RSA Cryptography Specifications Version 2.2,