System Architecture

Overview

HTMLTrust is a system for decentralized content authenticity, authorship claims, and endorsement. It defines a method for authors to sign content blocks in HTML, supported by canonicalization rules and cryptographic integrity checks, along with an endorsement and discovery model via public trust directories.

Signed HTML Blocks

A proposed new tag, <signed-section>, encapsulates a signed region of a page. This tag includes:

• Canonicalized content — e.g., a blog post or paragraph
• Metadata — author identity (e.g., via DID), timestamp, content hash
• Signature — Base64-encoded digital signature of content + metadata

<signed-section keyid="did:web:author.example"
    signature="BASE64_SIG" algorithm="ed25519"
    content-hash="sha256:abc123...">
  <meta name="author" content="Alice Example">
  <meta name="claim:ContentType" content="Article">
  <article>
    <h1>Verifiable Web Content</h1>
    <p>Content should be provable...</p>
  </article>
</signed-section>

Canonicalization

To ensure consistent signing and verification, content is canonicalized before hashing:

1. Normalize whitespace, strip extra line breaks
2. Sort HTML attributes and metadata
3. Minify and serialize as a UTF-8 string
4. Generate both SHA-256 hash and SimHash for similarity detection

Trust Directory (Optional)

Signed content MAY be submitted to one or more trust directories that:

• Index content hashes and associated signers
• Store and serve third-party endorsements
• Support key resolution and optional revocation

Endorsements

Third parties (publishers, experts, other users) can issue signed JSON endorsements of specific content hashes:

{
  "endorser": "did:web:publisher.org",
  "endorsement": "sha256-XYZ",
  "signature": "BASE64_SIG",
  "timestamp": "2025-05-01T00:00Z"
}

Browser Integration

Browser extensions (and eventually native browser support) verify:

• Signature validity via embedded or discovered public key
• Match of content hash to canonicalized DOM
• Trust status of signer and any endorsements

Trust configuration is client-side. UI indicators reflect verification status (e.g., a verified badge or a warning tooltip).

CMS Integration

Content management systems generate:

• Canonicalized content blocks
• Embedded signatures from author keys
• Optional submissions to trust directories

Reference implementations are available for WordPress with Hugo and other CMS support planned.

Reference Implementations