Confidential VM State-Separated Storage for Trusted Persistence

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Solution Overview

Problem

Confidential virtual machines face challenges in persisting their state between sessions due to the restricted trust boundary, which prevents data from leaving the secure environment, necessitating a new instance for any changes, and current solutions risk compromising the domain of trust by allowing the host to store the state.

Innovation Solution

Implementing a state-separated architecture using Merkle hash trees in the filesystem to maintain and validate the chain of trust, with read-only and read-write volumes, allowing state persistence and separation, ensuring data integrity and confidentiality beyond the trust boundary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If the host stores the state of confidential virtual machine outside the boundary of trust, then state persistence between sessions is enabled, but the domain of trust is compromised and data integrity cannot be guaranteed

Engineering Contradiction:

Improvestate persistence between sessionsVSAvoiddomain of trust

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

A state separation manager acts as an intermediary component that mediates between the confidential virtual machine and the host system. It manages state persistence in untrusted host memory while maintaining trust boundaries through cryptographic verification. The manager stores state data outside the confidential VM boundary but protects it using cryptographic proofs that verify data integrity without requiring trust in the host.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system segments state data into multiple components: confidential state data stored in untrusted host memory, cryptographic hashes stored in trusted locations, and verification metadata. This segmentation allows the system to separate the storage function (performed outside trust boundary) from the verification function (performed inside trust boundary), enabling persistence while maintaining reliability.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a new confidential virtual machine instance is created for every state change, then data confidentiality and integrity are maintained, but system complexity and resource consumption increase

Engineering Contradiction:

Improvedata confidentiality and integrityVSAvoidvirtual machine instantiation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of creating new VM instances for state changes, the system creates cryptographic copies (hashes) of the state data. These hash copies serve as verification tokens that prove the integrity of the actual state data stored elsewhere. This allows state evolution without VM instantiation, reducing complexity while maintaining integrity verification.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The system performs preliminary cryptographic hashing and verification setup during VM initialization. This preliminary action establishes the trust framework in advance, allowing subsequent state changes to be managed through simple hash comparisons rather than complex VM instantiation processes.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the host has limited or no access to the secure environment, then confidentiality is maintained, but state persistence and data portability are restricted

Engineering Contradiction:

ImproveconfidentialityVSAvoidstate persistence capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The state separation manager serves as an intermediary that enables state persistence without granting the host direct access to confidential data. It implements a controlled interface where the host can store and retrieve state data only through cryptographic verification, maintaining confidentiality while enabling persistence functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces direct mechanical/host access to state data with cryptographic verification mechanisms. Instead of the host reading or writing confidential state data directly, it interacts through cryptographic proofs and verified interfaces, substituting physical access control with mathematical trust verification.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12574262B2Confidential virtual machine using state-seperated storage architecture

Publication Date: 2026.03.10 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Examples of the present disclosure describe systems and methods for implementing a confidential virtual machine generation system. In examples, read-only and read-write volumes are generated to store operating system binaries and user-generated content, respectively, on filesystems indexed using hash trees. The hash values of the roots of the two hash trees are stored in a location accessed as part of loading an operating system. The example system accesses the roots of the two hash trees to access the current state of read-only and read-write volumes and verify the states using a checksum. The verified states are merged to generate an operating system image associated image with the confidential virtual machine. Additionally, the system merges the namespaces of filesystems of read-only and read-write volumes into a single filesystem namespace concealing multiple volumes.