Companion Agent
The local trust broker that enforces document access policies at the edge.
- Local Policy Enforcement Point (PEP) at every endpoint
- Hardware-backed device identity via TPM & Secure Enclave
- Trust decisions continue offline - fail-closed by default
User
Authenticated session
Companion Agent
Local trust broker
Device Identity
Hardware-backed
OSDF Policy Engine
Zero-trust PDP
Protected Document
Released under lease
One agent, five core roles
A trust broker that lives on the endpoint
The Companion Agent is the local control point between your users, their devices, and the OSDF policy engine - the same posture as a Tailscale client, Cloudflare WARP, or a CrowdStrike sensor, but for document access.
Runs in the tray
A lightweight background service in the system tray or menu bar - always present, never in the way.
Maintains authenticated sessions
Holds the user's identity-provider session and brokers it to the viewer and browser without re-prompting.
Verifies device identity
Proves a hardware-backed, non-exportable device key on every sensitive request.
Brokers access decisions
Evaluates permissions, posture, and leases locally to return an Allow / Warn / Deny verdict.
TPM & Secure Enclave interface
Talks to platform hardware security modules to generate, store, and use keys that never leave the device.
Smart-card infrastructure
Drives PKCS#11, CAC, and PIV middleware for credentialed authentication and signing.
Offline policy enforcement
Caches short-lived policy leases so access decisions keep working when connectivity doesn't.
How an access decision is made
Five deterministic steps run locally on every request - from the moment a user asks for a document to the signed audit event that records the verdict.
Step 1 / 5
User Requests Access
A user opens a protected document in the viewer or a browser tab. The request is routed to the local Companion Agent over a loopback channel - never to a remote decryption endpoint.
- Loopback request (127.0.0.1)
- Origin allowlist enforced
Native on every major OS
The Agent integrates with each platform's native credential store and hardware security module - no custom drivers required.
Windows
Windows 10 / 11 · Server 2019+
macOS
macOS 12 Monterey and later
Linux
Ubuntu, RHEL, Fedora, Debian
What makes the Agent a trust anchor
Device Identity
Hardware-backed, non-exportable keys bound to the TPM or Secure Enclave establish a verifiable machine identity.
SSO Broker
A secure bridge between the browser, the viewer, and your enterprise identity provider - sessions stay in the Agent.
Hardware Security
TPM, Secure Enclave, smart cards, and PKCS#11 tokens for key custody, attestation, and signing.
Offline Access
Short-lived, device-bound leases keep documents usable offline, then fail closed when they expire.
Signed Audit Trail
Every decision emits a tamper-evident, Ed25519-signed event - buffered locally and synced on reconnect.
Enforcement happens locally
The cloud issues policy and keys, but the decision to release plaintext is made on the device by the Agent. There is no bulk-decrypt endpoint and no master key.
- Local enforcement - verdicts computed at the edge
- Device binding - leases tied to hardware keys
- Origin allowlisting - only trusted callers reach the broker
- Fail-closed - absence of trust evidence denies access
OSDF Cloud
Key Broker · Trust registry
Policy Services
PDP · Lease issuance · Audit sink
Companion Agent
Local Policy Enforcement Point
A Policy Enforcement Point, by the book
The Companion Agent implements the PEP role defined by NIST SP 800-207: device-centric trust, continuous verification, and least-privilege access enforced at the resource boundary.
| Capability | How the Agent delivers it | Status |
|---|---|---|
| Identity Validation | Authenticated user session brokered from the IdP | Enforced |
| Device Trust | Hardware-backed key attestation and posture | Enforced |
| Policy Enforcement | Local PEP evaluates every access request | Enforced |
| Session Control | Short-lived leases, continuous re-verification | Enforced |
| Offline Decisions | Cached policy with fail-closed defaults | Enforced |
Trust status, always one glance away
The Agent surfaces its current trust posture in the system tray and menu bar. Watch it shift between Trusted, Degraded, and Locked - or pick a state to inspect it.
Protected & verified
Device attested · session active
- Session
- j.rivera@agency.gov
- Device trust
- TPM attested
- Policy lease
- valid · 4m 12s
- Connectivity
- online
- View Status
- Lock Agent
- Open Viewer
- View Recent Decisions
- Sign Out
Protected & verified
Device attested · session active
- View Status
- Lock Agent
- Open Viewer
- View Recent Decisions
- Sign Out
Trust decisions continue even when connectivity doesn't
Cached policy leases let the Agent keep making correct, least-privilege decisions on a disconnected or air-gapped endpoint. When a lease lapses, access fails closed - and every decision is signed for later audit.
- 00:00
Connectivity lost
Network drops mid-session. The Agent keeps running with its cached policy leases.
- 00:05
Local evaluation
Access requests are decided on-device against cached policy and device posture - no round trip.
- 04:00
Signed decision logs
Each verdict is signed and buffered locally as a tamper-evident audit event.
- 05:00
Lease expires → fail-closed
When the cached lease lifetime ends without renewal, access is denied by default.
- 06:30
Reconnect → logs synced
Connectivity returns; buffered audit events sync and fresh leases are issued.
Required infrastructure for regulated environments
Wherever a document's value depends on who, where, and when it is opened, the Companion Agent binds trust to the user, the device, the moment, and the policy.
Government
FIPS-validated hardware, PIV/CAC, and air-gap-friendly offline enforcement.
Defense
Device-bound trust on managed endpoints with signed, exportable audit.
Healthcare
Compartmented PHI access tied to enrolled clinical workstations.
Legal
Privileged-document control with verifiable, court-ready decision logs.
Enterprise
Zero-trust document access integrated with Entra, Okta, and MDM fleets.
Device-bound trust
Access is granted to a user + device + time + policy - never to a credential alone.
Deployment guideBring zero-trust enforcement to the endpoint
Roll out the Companion Agent across Windows, macOS, and Linux fleets with your existing MDM, and make every document access a verified, device-bound decision.