c2pa-warc 0.2.1

Overview

Stores and retrieves C2PA Manifest Stores in WARC 1.1 files (ISO 28500). The manifest is stored as a WARC record of a dedicated c2paprovenance type with Content-Type: application/c2pa, as the last record in the file.

WARC is used by national libraries, legal deposit systems, and digital preservation institutions to archive web content. This crate enables content provenance for archived web resources.

The C2PA Technical Specification defines no WARC embedding method. Unlike HTML, structured text, ZIP, ONNX, or SafeTensors — each of which has a normative clause — WARC embedding is a proposal, and what this crate implements is that proposed shape. It conforms to WARC 1.1 and produces a valid archive readable by any WARC tool; it does not claim C2PA specification conformance, because there is nothing yet to conform to.

Zero dependencies.

Quick Start

[dependencies]
c2pa-warc = "0.1"

Append a manifest

use c2pa_warc::append_manifest;

let warc_data: &[u8] = /* existing WARC file bytes */;
let manifest: &[u8] = /* C2PA manifest store bytes */;
let signed = append_manifest(warc_data, manifest, "urn:uuid:12345678-1234-1234-1234-123456789012").unwrap();

Read a manifest

use c2pa_warc::read_manifest;

let manifest = read_manifest(&warc_data).unwrap();

Multiple manifests

A WARC file carries at most one manifest record, always last. An update removes the existing manifest record and appends the replacement, which leaves the bytes of every other record unchanged. When WARC files are concatenated, the combining tool appends a fresh manifest covering all records in the combined file and removes the constituent manifest records, which may be referenced as ingredients.

Example

cargo run --example make_sample_warc writes a minimal WARC (examples/sample.warc) containing a warcinfo record, one captured response record, and a trailing c2paprovenance record whose block is a real C2PA Manifest Store, then extracts it back to examples/sample.manifest.c2pa. The manifest record header:

WARC/1.1
WARC-Type: c2paprovenance
WARC-Record-ID: <urn:uuid:...>
WARC-Date: ...
Content-Type: application/c2pa
Content-Length: 3576

Design

• Manifest stored as a WARC record of a dedicated c2paprovenance type, as the last record in the file; it carries no WARC-Target-URI
• At most one manifest record; an update removes the existing one and appends the replacement
• Manifest records are identified by WARC-Type: c2paprovenance together with Content-Type: application/c2pa

Scope

This crate implements embedding and extraction only. Content binding — the C2PA collection data hash, computed over each record's uncompressed bytes — is out of scope; use the official C2PA SDK to build and sign manifests.

Related Crates

Part of a family of single-purpose crates, one per C2PA embedding method. Each is standalone and independently versioned.

Security

Found a vulnerability? Please report it privately — see SECURITY.md.

License

Licensed under either of Apache License, Version 2.0 or MIT License at your option.

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