deCDN browser demo

decdn: links in any web page, opened through your local decdn gateway. Write

<img src="decdn:<hash>/path/to/image.png?ns=1">
<a href="decdn:<hash>/">a whole bundle</a>

and the browser shows the image and follows the link. The gateway fetches each file from deCDN nodes, checks every byte against its BLAKE3 hash, pays per megabyte under a capability a sponsor or a publisher issued, and streams the verified bytes back.

The Android and iOS demos run the same SDK inside an app; this one puts it behind the browser.

┌──────────────── browser ────────────────┐
│ page: <img src="decdn:…">               │
│   content.js rewrites it to the gateway │
│   background.js labels the request:     │
│   x-decdn-token, x-decdn-host           │
└────────────────────┬────────────────────┘
                     │ HTTP, loopback only
┌────────────────────▼────────────────────┐      ┌─────────────┐
│ decdn gateway                           ├─────▶│ deCDN nodes │  iroh QUIC, paid per MB
│   pays with the capability whose scope  │      └─────────────┘
│   covers the page's host                │
└─────────────────────────────────────────┘

• The gateway is the decdn gateway command of the decdn CLI. GET /<hash>[/<path>][?ns=<id>] serves decdn:<hash>[/<path>][?ns=<id>]: a file streams as it arrives, and a bundle (/<hash>/) gets a page listing its files. It holds one delegate key per capability, in memory only:
  • GET /_delegate mints a fresh key and returns its address. Every call returns a new address, so no site sees the same one twice and none can follow you across sites. A page calls it through CORS; the extension calls it with the gateway token. The pages of one site (subdomains included) hold at most a few keys, waiting or registered; the extension's own handshake is never limited.
  • PUT /_capability with {"capability": "dcap1:…", "scope": "…"} registers a capability issued to a minted address. Its owner signature must match the on-chain owner of its pool. A page registers through CORS, and its scope must cover its own host: example.com may register example.com, *.example.com or *, never another site, and never a wildcard over a public suffix such as *.io or *.github.io. The extension, with the gateway token, registers any scope.
  • A content request pays with the capability whose scope covers the page's host: an exact host first, then *.<domain>, then *.
• The extension (extension/) rewrites decdn: URLs in href, src, poster and data attributes to the gateway, including elements a page adds later, and labels the page's image, media and navigation requests to the gateway with the gateway token and the page's host. The browser adds those headers, so page scripts never see the token, and a page's own fetch() never carries it. The popup lists the gateway's capabilities and gets a sponsored one.
• Networking stays native. The gateway reaches nodes over direct QUIC like any decdn client, so the browser needs no WebTransport, WebRTC or relay.

The URI form is decdn:<hash>[/<path>][?ns=<id>]: the bare hash names a file, a trailing / a whole bundle, and a path one file inside it.

1. Install the decdn CLI and start the gateway:

   decdn gateway

   It listens on 127.0.0.1:8484 and prints its token, which it keeps in ~/.decdn/gateway/token. Until a decdn release includes decdn gateway, build it from the main branch of decdn/decdn with cargo build --release -p decdn-cli.

2. Load the extension. In Chrome or Brave, open chrome://extensions, turn on Developer mode, click Load unpacked, and pick the extension/ folder. In Firefox, open about:debugging#/runtime/this-firefox and Load Temporary Add-on with extension/manifest.json.

3. Open the extension's popup, paste the gateway token under Settings, and click Save.

4. Click Get a sponsored allowance and pass the check on the page that opens. The extension registers the capability the testnet sponsor at up.decdn.org issues, for every site (*). Open the popup again to see it.

5. Open the demo page, demo/index.html, from any web server, for example:

   python3 -m http.server 8600

   then http://127.0.0.1:8600/demo/. It shows an image from the Stable Diffusion XL bundle, and links to a test file, the Sintel 4K bundle, and a file inside it.

A publisher funds its own pages the same way, without the popup: its page calls GET /_delegate, its backend issues a capability to that address from its own pool, and the page registers it with PUT /_capability and a scope covering its host.

This is a demo. The gateway serves whole files in order and does not answer HTTP range requests yet, so a video cannot seek. It serves one download at a time. Delegate keys live in the gateway's memory, so a restart drops them and every capability issued to them; register again after one. A site whose scope covers a page can spend that capability on any decdn: content the page loads, up to the cap its issuer set.

Dual-licensed under either MIT or Apache-2.0, at your option.