Microsoft open-sources Project Tessera HSM stack

Microsoft released Project Tessera, an open-source evolution of its Azure Integrated HSM technology developed with Marvell, Oracle and the Open Compute Project. The release gives hardware and cloud teams access to the workload-attached hardware security module architecture, specifications, protocols, drivers, software, firmware and reproducible build environments.

A hardware security module (HSM) is dedicated hardware used to protect cryptographic keys. At the time of the research, Tessera’s public GitHub organization contained six repositories: specifications, register-transfer-level hardware code, a Linux driver, a Rust software development kit, a Unikraft fork and sidecar scripts. The project joins Microsoft’s broader infrastructure work, including its recent Maia 200 production deployment and Maia 300 plans.

Microsoft said it worked with Marvell to demonstrate Tessera transfer protocols at the 2026 OCP Global Summit. According to the company, the demonstration established HSM partition cloning and resiliency rings between a Tessera Integrated HSM and a Marvell LiquidSecurity 2 HSM.

The version 0.5.0 masking-key transfer specification explains how authorized HSM partitions can join the same security domain and use objects protected by a transferred masking key. It calls for authenticated Hybrid Public Key Encryption contexts, certificate validation, runtime attestation, policy checks, bidirectional key confirmation and audit evidence. The document credits contributors from Microsoft, Marvell and Oracle.

In Microsoft’s account, the cross-vendor demonstration kept non-extractable keys inside the participating HSMs, limited their availability to authorized partitions and left control with the partition owner. The sources reviewed did not independently test those security and interoperability outcomes.

Microsoft said Tessera also uses post-quantum cryptography for HSM-to-HSM communication. The specification defines post-quantum-only and hybrid classical/post-quantum encryption profiles, with authenticated negotiation and confirmation in both directions. The reviewed material did not include an independent audit or benchmark of the security, interoperability, performance or migration claims.

Microsoft described Tessera as designed to enforce FIPS 140-3 Level 3 key protection throughout a key’s lifecycle. The available evidence does not show that Tessera has completed that certification.

The project also includes a minimal, unikernel-based firmware stack for hardware-isolated confidential-computing environments, initially using AMD SEV-SNP and OpenVMM. Microsoft said it plans to add open-source silicon, hardware designs and community enhancements to the repositories as it works toward a fully open-source silicon implementation. It did not provide a delivery date.