A unidirectional data transfer protocol over HDMI for air-gapped environments.
VDXP encodes arbitrary binary data as visual cell patterns displayed on screen. The signal is captured via HDMI output and a USB capture device, then decoded to reconstruct the original data. No network connection. No USB drives.
[Sender] → Cell pattern on screen → HDMI → [USB Capture] → Decode → [Receiver]
- Sender splits a file into chunks, applies Reed-Solomon error correction, and renders each chunk as a grid of colored (or grayscale) cells on the HDMI output.
- Capture device digitizes the HDMI signal via USB.
- Receiver decodes cell values, corrects errors via RS, and reassembles the original file.
- Cell grid encoding — The display is divided into a uniform grid of cells. Each cell carries multiple bits of data encoded as a color or grayscale level.
- Color palettes — BGR 8-color (cube vertices) for lossy-compressed capture; Y-only grayscale (Y16/Y32/Y64) for uncompressed capture.
- Reed-Solomon error correction — Per-block FEC over GF(2^8) enables reliable transfer even with capture artifacts.
- 3-stage decode filter — Fingerprint check → Header-only decode → Full decode. Minimizes CPU load by rejecting duplicates early.
- Loop playback — Sender displays frames in a continuous loop; receiver collects until all unique frames are received.
- Unidirectional — Data flows one way only (display → capture). No return channel.
- Air-gap safe — Works across physically isolated networks using only HDMI + USB capture.
- Hardware agnostic — Works with any HDMI output and USB capture device.
- Integrity — Reed-Solomon provides per-block error detection/correction. Application-layer hash verification (e.g., SHA-256) is recommended for end-to-end validation.
| Configuration | Throughput | Hardware |
|---|---|---|
| Basic (MJPEG, 8-color) | ~100 KB/s | USB2.0 MJPEG capture (~¥15,000) |
| Standard (YUY2, Y16) | ~1,000 KB/s | USB3.0 YUY2 device |
| Accelerated (YUY2, Y32) | ~15,000 KB/s | USB3.0 YUY2 + accelerated decoder |
VDXP is currently implemented in vdxpy. The encoding format is defined by the reference implementation and may evolve based on real-world usage. A formal protocol specification will be published when interoperability with independent implementations becomes a priority.
| Name | Language | License | Description |
|---|---|---|---|
| vdxpy | Python | MIT | Reference implementation |
This document is released under the CC-BY-4.0 license.
- Black Ocean Technologies — blackocean.tech
- Enterprise / government inquiries: contact@blackocean.tech