# Sia / Skynet

Use `sia://<skylink>[/path]`. This is the Skylink format represented by ENS
contenthash tooling, not an arbitrary file path on the Sia network.
The ENS codec is named `skynet`, while ENSjs uses the protocol label `sia`.
See the [ENS content-hash library](https://github.com/ensdomains/content-hash).

Apply the [shared retrieval rules](/implementers/proof-retrieval). Reject URI
queries and fragments. Do not interpret the Skylink as a gateway hostname.

## Retrieval

1. Decode and validate the Skylink with a format-aware implementation. Preserve
   case and reject invalid lengths, encodings, or version bits.
2. For a direct link, verify the requested data against the link's content
   commitment, including the selected byte range and file metadata.
3. For a resolver link, validate the signed registry entry and its binding to
   the link before following the referenced content. Check revision ordering
   against any newer entry already known to the client.
4. Resolve the requested file path through the verified metadata. Do not accept
   a portal's error page or an unrelated default file for a missing path.
5. Extract one file, then apply the proof format and envelope size rules.

Use a verifying node or obtain the evidence needed to check the content and
registry mapping. Do not treat a portal response or a repeated Skylink header
as an integrity proof. Mutable links require bounded resolution and loop detection.

The archived [Skynet client source](https://github.com/SkynetLabs/skynet-js)
provides protocol context. Its existence does not imply that its former default
portal is available. Configure the node or portal explicitly; do not hard-code
a public service as a requirement of verification.

## Availability and Caching

Cache verified immutable files by link and path. Refresh mutable registry mappings
before reusing a result; a valid old signature does not establish the latest revision.

If the client cannot validate a link version or cannot reach a provider, report
that limitation. Do not silently turn the location into an ordinary HTTPS proof
and skip Skylink validation.