Securing The SoC Life Cycle

Over the course of its life, an SoC (system on chip) goes through multiple life cycle states which are different in character and have varying and sometimes contradictory security requirements. In each state, the SoC may be under different ownership in the supply chain. Also, as it transitions through different manufacturing phases, it is subject to a different set of possible attacks, which should all be addressed with the help of a solution that is easy to manage and track. It is the goal of secure silicon life cycle management to allow a strong hardware enforcement of these requirements.

Blank – This is the initial state of the SoC that typically just left the wafer fab or packaging facility. At this stage, the SoC has no personalized identity and no provisioned secrets. All SoCs from a lot are the same and all test interfaces are open to allow maximum coverage of the silicon health. Despite the lack of secrets or ID, this is a sensitive state. Intellectual Property in the silicon logic could be stolen, or the entire die could be reverse-engineered or over-produced.

Personalized (Tested) – Following the completion of testing and the locking of test capabilities, the SoC gets its personalization, in which a unique ID code is written into the device’s OTP (one time programmable [non volatile memory]) or captured through an unclonable function. From this point forward, each device is unique, even though they were produced in the same batch and bear identical product numbers. Now, we have traceability to track for stolen parts or over-production.

Provisioned – Here, unique primary keys, typically created by the chip manufacturer, are provisioned into the device in a known secure area. At the end of provisioning process, the secure area is locked against further access from the outside. This state may be divided into sub-states, with the OTP split into controlled regions, each managed by a different entity in the supply chain. At any such sub-state, keys are provisioned and checked, and then that region is locked against external access (reads or writes).

Deployed – Until now, software developers could develop and debug their code freely. Now, with the parts deployed to the field, the device prohibits debug and enforces a Secure Boot. In the Deployed state, the application software becomes an important asset to protect. It must be proven to be owned and signed by the OEM (authentication), unmodified (integrity-checked) and very likely, encrypted (confidentiality). These checks are implemented during the Secure Boot process. In addition, access to the software from the debug port must be blocked as a condition for deployment.

Re-sale – At times, chips or devices can be re-sold, in which case ownership rights should be transitioned to the new owner. In some cases, ownership transition involves obliterating or replacing the OTP keys initially provisioned. As examples: in certain Data Center environments, the servers may be re-sold to enterprises as the Data Center acquires newer and more powerful equipment. In this case, typically the OTP needs to be cleaned up from secrets. Another example is the selling of an autonomous car to a new owner. In this case (as well as others such as laptops, cell phones and their likes), typically a ‘factory reset’ procedure must be run to clean up secrets prior to passing ownership.

Field Return (RMA) – This state is used whenever a malfunction is uncovered after deployment, and the device is returned to the original manufacturer to debug the malfunction. When transitioning to this state, debug is re-enabled, but secrets that can be linked to the user’s account and privacy must be destroyed.

End of Life (Decommissioned) – Here product service comes to an end. The equipment is decommissioned altogether, and all secrets are destroyed before the device is discarded. If decommissioning is not managed properly, an end-of-life (EOL) SoC could be harvested and re-introduced into the supply chain as a “new or resold” device.

The procedure to transition between life-cycle states must be very secure. Hackers may try to physically roll back a single device to an earlier state to extract software and keys, or remotely try to move a device to end of life and bring the entire deployment down. Any physical attempt to tamper with the life cycle state should cause the device to transition to the EOL state. Likewise, any remote attacks must be detected, blocked, and reported as security events. Thus, a lot of attention is needed to protect the life cycle state data.

As can be seen, many security mechanisms are tightly entangled with the life cycle state. In order to keep them well orchestrated and functioning, secure silicon life cycle management must be centralized and easy to understand, program and follow. In addition, attestation of life cycle states via the cloud is required.

At the foundation of secure silicon life cycle management is a hardware root of trust embedded in the SoC. The Root of Trust securely stores provisioned keys and secrets, and provides cryptographic accelerators for functions such as encryption, authentication, and key derivation.

Rambus offers a comprehensive suite of Root of Trust solutions ranging from compact state machine-based solutions (RT-100 series) to powerful secure co-processor based Root of Trusts (RT-600 series). These Root of Trust solutions protect the SoC against a wide range of hardware and software attacks with state-of-the-art anti-tamper and side channel attack resistance. In addition, the Root of Trust provide hardware-accelerated cryptographic services to (security) applications in the SoC. For devices from IoT to the core of the data center, Rambus has a Root of Trust solution for every application. Rambus Secure Manufacturing provisioning infrastructure and Secure Key Management solutions complement the Root of Trust solutions.

With the anti-tamper and security safeguards of a Rambus Root of Trust, an SoC is protected post-provisioning during any life cycle stage. In addition, the Root of Trust protects SoCs between life cycle states. A secure life cycle management module in the Root of Trust is responsible to smoothly manage the life cycle features and transitions while protecting life cycle state data. The module supports attestation of the SoC’s life cycle state via a cloud-based key management system.

Over the course of its life, an SoC goes through multiple ownership and operating states which are different in character and have differing security requirements. Management of these requirements is enabled by a Root of Trust anchored in the hardware of the SoC. With an industry leading portfolio of Root of Trust solutions, and renowned experience in silicon security, Rambus is best suited for helping chip and device manufacturers protect products and data during the entire silicon life cycle.

Additional resources:

• Website: Rambus Root of Trust Solutions
• Website: Rambus Provisioning and Key Management