Axiado Corporation, a leading AI-driven, hardware-anchored platform security solutions provides a unique integration of Caliptra into its security products built upon Axiado’s deep security expertise and extensive experience with datacenter technologies. The seamless integration of Axiado TCU with Caliptra offers datacenter customers a unique opportunity to enhance platform security with flexibility.

Axiado Trusted Compute/Control Unit (TCU)
The Axiado TCU is a single-chip security processor enforcing Zero-Trust principles and attack mitigation for servers and networks thanks to a rich environment of security controls. It features a quad-core CPU, a Secure Vault™, a neural network processor for AI-powered security features, and a hardware firewall for network traffic protection.

Figure 1: Axiado TCU and Caliptra

The TCU comprises two major sections: the Trusted Computing Base (TCB) and the user-accessible section. The TCB provides essential security services such as cryptographic operations, secure storage, attestation, and trusted computation. These services are enabled by secure enclaves isolated from the rest of the chip to prevent interference and unauthorized access. Meanwhile, the user-accessible section provides network protection, security applications, and machine learning enabled detection and prevention mechanisms. Together, these two sections deliver comprehensive protection for critical systems.

The user-accessible section of the Axiado TCU is designed to empower users with security management, advanced threat detection, powerful application support, and network firewall capabilities.

The Trusted Computing Base (TCB) of the Axiado TCU provides the user-accessible section with the security foundation it requires to deliver security services with confidentiality, integrity, and availability. The TCB comprises two key components: the Secure Vault and Caliptra.

The Secure Vault is a Hardware Security Module (HSM) that establishes a foundation for platform security. It features a dedicated secure enclave with hardware-secured immutable code, ensuring that any firmware or software running on the TCU is always validated and optionally decrypted before use. This enclave offers FIPS 140-3 Level 2 certified cryptographic services, ensuring accurate and confidential cryptographic operations. Secure Vault thus provides Secure Boot, Secure Update, and Secure Recovery Services.

Caliptra
Caliptra, the second key component of the TCB, is an open-source Root of Trust for Measurement (RTM) and Root of Trust for Identity (RTI) promoted by the Open Compute Project (OCP). The measurement of firmware images or other data and the detection of their corruption is directly linked to Caliptra’s attestation capabilities, which include its ability to cryptographically verify information and data integrity. As a matter of fact, Caliptra also measures the Secure Vault firmware images, ensuring that they are genuine before Secure Vault runs them.

As soft IP integrated in the Axiado TCU design, Caliptra provides datacenter operators with cryptographically verifiable proof to ensure that only authorized firmware images are in production. Caliptra is an open-source design supported by industry leaders such as Google, AMD, and Microsoft. It can be used with several security protocols like the Security Protocols and Data Model (SPDM) from the Distributed Management Task Force (DMTF) or the Device Identity Composition Engine (DICE) from the Trusted Computing Group (TCG). The open-source nature of Caliptra is an application of Kerckhoff’s principle, aiming at ensuring that the security of the Caliptra solution only relies on the secret keys it manipulates and not on the confidentiality of its design. In addition, the transparency of the design ensures consistency in its implementation, which is conducive to the scalability required in large data center deployments. Caliptra gives datacenter operators essential tools to verify firmware authenticity and build state-of-the-art zero-trust architectures.

Axiado provides a unique integration of Caliptra into its security products leveraging its deep security expertise and experience with datacenter technologies. With the Axiado design, the Secure Vault wraps around the Caliptra design, filtering any direct access to its interfaces. The Secure Vault protects the interaction between Caliptra and external entities by being the only component that can directly access the Caliptra mailbox. No other design component can do so, enabling the Secure Vault to filter all access to Caliptra. The Secure Vault securely implements the Caliptra specification V1.0 Passive Profile and loads Caliptra’s firmware into its mailbox upon startup. The Secure Vault realizes a secure enclave separated from the rest of the SoC by a hardware-enforced secure boundary.

The Secure Vault consists of two secure processors, one dedicated to sequencing cryptographic operations that it accelerates using dedicated hardware components for symmetric and asymmetric algorithms, and the other dedicated to providing secure services outside the TCB. The Secure Vault also provides the Caliptra design with fuses in One Time Programmable (OTP) memory that are required to store its secrets and SRAM for the Caliptra mailbox and its RISC-V computations.

A crucial aspect of the Caliptra design is its reliance on a Unique Device Secret (UDS) that is not accessible by and unknown to any external source. Caliptra is, therefore, also a Root-of-Trust for Identity (RoTI) in addition to being a RoTM. Axiado realizes this essential requirement by adding a Physically Unclonable Function (PUF) to its design and making the PUF output available to the Caliptra Root-of-Trust (RoT). The PUF enables the Axiado integration of Caliptra to implement a reliable Device Identity Composition Engine (DICE) and ensure the unicity of Axiado DICE identities. The Secure Vault complements Caliptra by serving as a Root-of-Trust for Update (RTU) and a Root-of-Trust for Recovery (RTRec), aligning with the firmware protection and recovery principles outlined in the platform resiliency guidelines from NIST (NIST SP 800-193). Caliptra performs all the measurements of the Secure Vault firmware images and stores them.

Axiado TCU Integration with Caliptra
Axiado successfully demonstrated the interoperability of its Caliptra implementation with cloud platforms based on AMD EPYC Genoa and Turin server processors. Axiado demonstrated the implementation of the Security Protocol and Data Model (SPDM) specification running on our Secure Vault and using Caliptra for DICE and DICE Protection Environment (DPE) identity management and attestation calls. In that scenario, the Axiado TCU acts as a Platform Root-of-Trust (PRoT) and SPDM requester interacting with an AMD Genoa-based server acting as an SPDM responder.

Finally, the Axiado design is flexible, and customers can also configure the Secure Vault subsystem to bypass Caliptra and act as a RoT for Measurement. Its FIPS 140-3 Level 2 certified cryptographic engine ensures the correctness of all its cryptographic computations, and the Secure Vault is directly connected to the same PUF available to Caliptra.

Availability
Axiado’s AX3000 and AX2000 TCUs as well as OCP DC-SCM 2.0 Compliant Axiado SCM3002 and Axiado SCM3003 are available now for purchase. Please contact Axiado for samples and pricing.