Crate c2pa_unstructured_text 

C2PA manifest embedding and hard binding for unstructured text.

Implements the Embedding Manifests into Unstructured Text section of the C2PA Technical Specification, which carries a C2PA Manifest Store inside a Unicode text stream as a run of non-rendering variation selectors, so that provenance survives copy and paste between systems that have no file.

The specification describes this method as one that should only be used where no other embedding method is feasible. For source code, configuration, and markup, prefer the structured-text method in c2pa-structured-text; for HTML, prefer the dedicated HTML method.

Scope

• Frame (wrapper): encode, embed, locate, and strip the C2PATextManifestWrapper, plus the specified deterministic padding.
• Hard binding (hardbinding): the exact c2pa.hash.data coverage, with compute and verify.

Signature verification, certificate trust, and assertion validation are not implemented here.

Zero dependencies by default

The frame and the binding algorithm pull nothing in. Hashing and NFC are injected through hardbinding::Hasher and hardbinding::Normalizer, so a host that already provides them (a Cloudflare Worker, a browser) supplies its own. Enabling hard-binding adds ready-made implementations; it adds convenience, never capability.

Examples

Embed a Manifest Store and recover it:

use c2pa_unstructured_text::wrapper;

let asset = wrapper::embed("Hello world.", b"manifest-bytes").unwrap();
assert_eq!(wrapper::extract(&asset).unwrap().payload, b"manifest-bytes");

The wrapper is invisible, so the visible text is unchanged:

use c2pa_unstructured_text::wrapper;

let asset = wrapper::embed("Hello world.", b"m").unwrap();
let w = wrapper::extract(&asset).unwrap();
assert_eq!(wrapper::strip(&asset, w.range()).unwrap(), "Hello world.");

Bind the visible text:

use c2pa_unstructured_text::hardbinding::{
    compute_data_hash, verify_data_hash, Algorithm, RustCrypto, UnicodeNfc,
};
use c2pa_unstructured_text::wrapper;

let asset = wrapper::embed("Hello world.", b"manifest-bytes").unwrap();
let binding =
    compute_data_hash(&asset, Algorithm::Sha256, &RustCrypto, &UnicodeNfc).unwrap();

assert!(verify_data_hash(&asset, &binding, &RustCrypto, &UnicodeNfc).is_ok());

Relationship to the structured-text binding

Both crates expose the same shape, so a dispatcher can treat them alike, but the coverage rules differ deliberately. A.9 hashes the raw file bytes with no normalization, because structured text is byte-stable on disk. A.8 removes the wrapper and then normalizes to NFC, because the text is clipboard portable and may arrive in any normalization form. Offsets are into the text as stored in both cases.

Features

• hard-binding — hardbinding::RustCrypto and hardbinding::UnicodeNfc (pulls sha2 and unicode-normalization).
• checksum-v2 — a v2 frame carrying a truncated hash over the header and payload, so a mangled carrier is rejected rather than decoded to wrong bytes. A WritersLogic extension, not part of the specified frame.

No feature is enabled by default.

Re-exports

pub use error::Error;

pub use hardbinding::Algorithm;

pub use hardbinding::DataHash;

pub use hardbinding::Exclusion;

pub use hardbinding::Hasher;

pub use hardbinding::Normalizer;

pub use wrapper::Wrapper;

pub use wrapper::MAGIC;

pub use wrapper::MARKER;

pub use wrapper::VERSION;

Modules

error

hardbinding

The c2pa.hash.data hard binding for unstructured text (A.8).

vs

The variation-selector byte codec (C2PA 2.4 Appendix A.8).

wrapper

The C2PATextManifestWrapper frame (C2PA 2.4 Appendix A.8).