PG-Presence
The Attack Surface Nobody Else Can Close.
Patented optical distance bounding confirms the verified person is physically present at their device — not operating remotely through a screen share, KVM switch, or virtual camera.
What PG-Presence Does
PG-Presence uses optical distance bounding — a QR code challenge-response protocol measured over approximately 5 seconds — to confirm the mobile device is physically co-located with the person on camera. Each round-trip verification completes in under ~100ms.
Optical Challenge
QR code displayed on the meeting screen encodes a unique, time-bound cryptographic challenge.
Device Response
Polyguard Mobile captures the QR code optically, signs the response in the device's secure enclave, and transmits the attestation.
Distance Bound
The round-trip timing (under ~100ms) physically constrains how far the device can be from the screen. Remote interception is impossible within these bounds.
Patented Technology
PG-Presence is protected by issued and pending patents covering optical distance bounding for identity verification.
Attack Surfaces PG-Presence Closes
Every attack that separates the verified person from the device they appear to be using.
Remote Desktop
An attacker accesses the victim's machine remotely and joins a meeting as them. The verified person is not physically present. PG-Presence confirms co-location with the device — remote desktop fails the distance bound.
Screen Sharing Relay
An attacker views the victim's screen through a screen share and relays the QR challenge to a remote device. The optical round-trip exceeds the distance bound, and the relay is stopped.
KVM Switch
A hardware device allows an attacker to control the victim's machine from another location. The person on camera is not physically at the device. PG-Presence requires the mobile device to optically read the screen in person.
Virtual Camera Injection
Software-based cameras inject pre-recorded or deepfake video into the meeting. PG-Presence operates independently of the video feed — it verifies physical presence through the optical channel, not through the camera stream.
Why Liveness Is Not Enough
Existing liveness solutions confirm that a real face is in front of the camera. That is necessary, but it is not sufficient. A real face can be in front of a camera while the device is controlled remotely.
"Liveness tells you the face is real. PG-Presence tells you the person is actually in the room."
Liveness vs. PG-Presence
Coverage across attack types.
| Attack Type | Liveness Only | PG-Presence |
|---|---|---|
| 2D Photo / Printed Image | ||
| Video Replay | ||
| 3D Mask / Prosthetic | Partial | |
| Remote Desktop | ||
| Screen Sharing Relay | ||
| KVM Switch | ||
| Virtual Camera Injection |
How It Works
Optical Distance Bounding
Distance bounding protocols use the speed of light to establish an upper bound on the physical distance between two parties. PG-Presence implements this optically: a cryptographic challenge is rendered as a QR code on the meeting screen, and Polyguard Mobile must capture it with the device camera. The round-trip time — from challenge display to signed response — physically constrains how far the device can be from the screen.
QR Code Challenge-Response
Each challenge is unique, time-bound, and cryptographically signed. The QR code encodes a nonce, timestamp, and session identifier. Polyguard Mobile reads the code, signs the response with the device's secure enclave key, and transmits the attestation. The entire exchange takes approximately 5 seconds, with the critical distance-bound measurement completing in under ~100ms.
Why It Cannot Be Replayed or Simulated
Three properties make replay and simulation impossible. First, each challenge includes a unique nonce — replaying a previous response fails validation. Second, the response is signed by a hardware-backed key that cannot be extracted from the device. Third, the timing constraint means any relay through a network (screen share, video feed, remote desktop) adds latency that exceeds the distance bound. The physics of light propagation enforce what software alone cannot.
See PG-Presence in Action
Access the Polyguard sandbox and experience optical distance bounding firsthand.