Caliptra

Caliptra consists of IP and firmware for an integrated Root of Trust block.

Caliptra targets datacenter-class SoCs like CPUs, GPUs, DPUs, TPUs. It is the specification, silicon logic, ROM and firmware for implementing a Root of Trust for Measurement (RTM) block inside an SoC. A Caliptra integration provides the SoC with Identity, Measured Boot and Attestation capabilities.

Organizations

Caliptra is a project originally incepted at the Open Compute Project (OCP). The major revisions of the Caliptra specifications are published at OCP. The evolving source code and documentation for Caliptra live in this repository within the CHIPS Alliance Project, a Series of LF Projects, LLC.

Governance

The Caliptra WorkGroup Technical Charter sets out the charter governing the Caliptra project.

Trademark

• Caliptra Trademark Policy
• Caliptra Trademark Process definition
• Caliptra Trademark Checklist and Evaluation Methodology

Specifications

Caliptra 1.x:

• Main Caliptra specification 1.x
• Caliptra Core Hardware Specification
• Caliptra Core Hardware Integration Specification
• ROM 1.x
• FMC
• Runtime

Caliptra 2.x:

• Main Caliptra specification 2.0 - Version 1.0
• Caliptra Core Hardware Specification 2.0.1
• Caliptra Core Hardware Integration Specification 2.0.1
• Caliptra Subsystem Hardware Specification - Version 1.0rc1
• Caliptra Subsystem Integration Specification - Version 1.0rc1
• ROM 2.x - WIP
• FMC 2.x - WIP
• Runtime 2.x - WIP
• MCU Firmware and SDK specification - WIP

Versioning

Caliptra is released in independently versioned components: RTL, ROM, FMC and Runtime FW. They are all represented by 3 values: major.minor.patch (such as 1.0.2). The first 2 values, major.minor, correspond to a set of features caliptra supports. The patch value is incremented as new releases are made with bug fixes. Lastly, mutable firmware (FMC/FW) have security version numbers (SVNs) that are incremented as required by when addressing security-critical issues. These are specified with the label (svn/svn) for (FMC/FW) versions respectively.

Not all components necessarily need to be of the same major.minor version to be compatible. Details are below:

Caliptra 1.0

Compatible Configurations:

RTL	ROM	Runtime FMC/FW
1.0.x	1.0.x	1.0.x (0/0)

Caliptra 1.1

Additional Features

• ECC HW performance enhancements*
• LMS HW acceleration*
• New Runtime commands
  • LMS_SIGNATURE_VERIFY
  • ADD_SUBJECT_ALT_NAME
  • CERTIFY_KEY_EXTENDED
• Expanded PL0 contexts to 16

* Requires 1.1 RTL

Compatible Configurations:

RTL	ROM	Runtime FMC/FW
1.1.x	1.1.x	1.1.x (0/0)
1.0.x	1.0.x	1.1.x (0/0)

Caliptra 1.2

Additional Features

• Manifest-based Authorization
  • SET_AUTH_MANIFEST
  • AUTHORIZE_AND_STASH
• Deferred retrieval of IDEV CSR**
  • GET_IDEVID_CSR
• Self-signed FMC Alias CSR
  • GET_FMC_ALIAS_CSR
• DPE export of CDI
  • SIGN_WITH_EXPORTED_ECDSA
  • REVOKE_EXPORTED_CDI_HANDLE
• DPE max cert size increased to 6kB

** Requires 1.2 ROM

Compatible Configurations:

RTL	ROM	Runtime FMC/FW
1.1.x	1.2.x	1.2.x (0/0)
1.1.x	1.1.x	1.2.x (0/0)
1.0.x	1.0.x	1.2.x (0/0)

Caliptra 2.0

Additional Features

• Support ML-DSA Caliptra FW Signature
• Support OCP Recovery
• Support Caliptra Sub-System
• IDevID CSR HMAC Signing
• Crypto Offload Mailbox Services

*** Only RTL release versions 2.0.2+ should be used due to ROM compatibility requirements.

Compatible Configurations:

RTL	ROM	Runtime FMC/FW
2.0.2+	2.0.x	2.0.x (0/0)

Caliptra 2.1

Additional Features

• Support ML-KEM in Adams Bridge
• Support for ML-DSA External-Mu mode in Adams Bridge
• Support OCP L.O.C.K.
• Support for AES DMA mode
• Caliptra Core mailbox size reduced to 16 KiB in subsystem mode

Compatible Configurations:

RTL	ROM	Runtime FMC/FW
2.1.x	2.1.x	2.1.x (0/0)

Test Dashboards

• Caliptra Software CI dashboard -- includes ROM
• Caliptra CPU DV coverage dashboard

Repositories

The Caliptra code base and documentation are split across several repositories:

Repository	Areas of interest	Description
Primary repository	Issues, PRs, Security advisories	This repository, with admin boilerplate and docs
Adams Bridge RTL	Issues, PRs, Security advisories	The primary repository with Adams Bridge Post-Quantum Cryptography hardware accelerator
Caliptra RTL	Issues, PRs, Security advisories, internal registers, external registers	The primary repository with immutable RTL
Caliptra Software 1.x	Issues, PRs, Security advisories	Caliptra software (ROM, FMC, runtime firmware), and libraries/tools needed to build and test
Caliptra Software 2.x	Issues, PRs, Security advisories	Caliptra software (ROM, FMC, runtime firmware), and libraries/tools needed to build and test
Caliptra DPE	Issues, PRs, Security advisories	An implementation of a TCG DICE Protection Environment profile
Caliptra U-Reg	Issues, PRs, Security advisories	General-purpose libraries and tools for manipulating MMIO registers from Rust
Caliptra Subsystem	Issues, PRs, Security advisories, registers	Caliptra Subsystem including Manufacturer Control Unit (MCU) and peripherals
Caliptra MCU Software	Issues, PRs, Security advisories	Caliptra MCU Firmware and SDK and specification
I3C Core	Issues, PRs, Security advisories	I3C target core developed for Caliptra

The GitHub config parameters for all of the branches are documented in a local file.

GitHub branch names for caliptra-sw are documented in its BRANCHING_STRATEGY.md.

Convenience repository URLs

All these URLs redirect into the repositories above.

• repo.caliptra.io
• spec.caliptra.io
• sw.caliptra.io
• fw.caliptra.io
• hw.caliptra.io
• rtl.caliptra.io
• dpe.caliptra.io
• ureg.caliptra.io
• ireg[s].caliptra.io
• ereg[s].caliptra.io

Security policy

For information on the Caliptra security policy, how to report a vulnerability, and published security advisories, refer to Caliptra security policy.

Discussion Channels

The Caliptra workgroup meets every Thursday at 1pm PT. Meeting invite and agenda are posted to the mailing list. You can join the call directly using this link.

A Slack channel is used for interactive discussions. Keep in mind development activity is focused on GitHub issues and Pull Request reviews, rarely on the Slack channel. If you have issues joining please contact the mailing list.

Please sign the CHIPS CLA (as an individual or your company if affiliated) before participating in these channels.

License

All code written for Caliptra and found in these repositories is licensed under the Apache Source License 2.0. You can find out more by reading our document on how to contribute.