| # OpenTitan Security Model Specification |
| |
| The current version of the security model targets discrete silicon |
| implementations of OpenTitan. The architecture for an integrated IP solution |
| will be covered in a future release of this specification. |
| |
| The following diagram shows the interaction between the different specification |
| components. |
| |
| <img src="documents.svg" style="width: 900px;"> |
| |
| |
| ## [Device Life Cycle][device_life_cycle] |
| |
| OpenTitan supports a set of operational states configured via One Time |
| Programmable (OTP) memory, allowing the [Silicon Creator][silicon_creator] to |
| manage the state of the device as it is being manufactured and provisioned for |
| shipment. |
| |
| An additional set of life cycle states are also available to encapsulate the |
| device ownership state. A device that has been personalized with a unique |
| [Creator Identity][creator_identity] can be provisioned with |
| [Silicon Owner][silicon_owner] credentials. This enables the |
| [Silicon Owner][silicon_owner] to run signed code on the device. |
| |
| ## [Secure Boot][secure_boot] |
| |
| OpenTitan supports a secure boot implementation anchored in the silicon ROM. |
| The ROM contains a set of public keys used to verify the first boot stage |
| stored in flash. |
| |
| Each boot stage is in charge of verifying the signature of the next stage and |
| locking out portions of the chip that are not required by later stages. Once the |
| boot flow reaches kernel execution, the implementation may opt to implement |
| dynamic isolation between applications using the available |
| [Physical Memory Protection][pmp] (PMP) unit. |
| |
| ## [Firmware Update][firmware_update] |
| |
| OpenTitan supports a firmware layout with two flash partitions, supporting |
| active and non-active instances of each software component. This enables a |
| firmware update implementation in which the active partition flashes the new |
| software into the non-active region with minimal downtime. Secure boot ensures |
| the integrity and stability of the new software before marking it as active. |
| |
| ## [Identities and Root Keys][identities_and_root_keys] |
| |
| This document describes the composition of the Silicon Creator and Silicon Owner |
| cryptographic identities, as well as the device’s key derivation scheme. This |
| scheme is based on a symmetric key manager with support for software binding and |
| key versioning. |
| |
| ## [Attestation][attestation] |
| |
| Covers the mechanism in which software verifies the authenticity and integrity |
| of OpenTitan's hardware and software configuration. |
| |
| ## [Ownership Transfer][ownership_transfer] |
| |
| The owner of the silicon is allowed to change in a process known as Ownership |
| Transfer. During this process, a new party can take ownership of the device and |
| provision its own identity. This allows the new owner to run its own signed code |
| and configure its attestation chain. |
| |
| ## [Provisioning][provisioning] |
| |
| Describes manufacturing and post-ownership transfer provisioning flows. Secrets |
| required to personalize the identity of the device and initialize security |
| countermeasures are provisioned at manufacturing time. Silicon owners have the |
| option of provisioning additional secrets after taking ownership of the device. |
| |
| |
| [attestation]: ./attestation/README.md |
| [creator_identity]: ./identities_and_root_keys/README.md#creator-identity |
| [device_life_cycle]: ./device_life_cycle/README.md |
| [firmware_update]: ./firmware_update/README.md |
| [identities_and_root_keys]: ./identities_and_root_keys/README.md |
| [ownership_transfer]: ./ownership_transfer/README.md |
| [pmp]: https://ibex-core.readthedocs.io/en/latest/03_reference/pmp.html |
| [provisioning]: ./device_provisioning/README.md |
| [secure_boot]: ./secure_boot/README.md |
| [silicon_creator]: ../logical_security_model/README.md#silicon-creator |
| [silicon_owner]: ../logical_security_model/README.md#silicon-owner |
