Function attest_value

atomic-canonical/src/proof.rs:113–151

Generic attest over a JSON-LD value — the *one* canonicalization/signing path all typed nodes share. Fills `attributedTo` (from the identity's `did:atomic`) when absent, computes the content hash over `hashing_view`, signs `jcs(signing_view)`, and attaches the proof. Returns the value.

(mut value: Value, identity: &Identity, keypair: &KeyPair)

/// `did:atomic`) when absent, computes the content hash over `hashing_view`,
/// signs `jcs(signing_view)`, and attaches the proof. Returns the value.
pub fn attest_value(mut value: Value, identity: &Identity, keypair: &KeyPair) -> Value {
    let did = did::did_for_public_key(&identity.public_key);

    if let Some(obj) = value.as_object_mut() {
        // Fill attributedTo only if there is no non-empty value already.
        let has_author = obj
            .get(PROP_ATTRIBUTED_TO)
            .and_then(Value::as_str)
            .map(|s| !s.is_empty())
            .unwrap_or(false);
        if !has_author {
            obj.insert(PROP_ATTRIBUTED_TO.to_string(), Value::String(did.clone()));
        }
    }

    // Hash first (over the value without proof/contentHash), then sign (over
    // the value with contentHash, without proof).
    let content_hash = hash::content_hash(&hashing_view(&value));
    if let Some(obj) = value.as_object_mut() {
        obj.insert(PROP_CONTENT_HASH.to_string(), Value::String(content_hash));
    }

    let signing_bytes = jcs::canonicalize(&signing_view(&value)).into_bytes();
    let signature = Signer::new(keypair).sign(&signing_bytes);
    let proof = Proof {
        type_: PROOF_TYPE.to_string(),
        cryptosuite: CRYPTOSUITE.to_string(),
        verification_method: did::verification_method(&did),
        proof_purpose: PROOF_PURPOSE.to_string(),
        proof_value: encode_proof_value(&signature),
    };
    if let Some(obj) = value.as_object_mut() {
        obj.insert(
            PROP_PROOF.to_string(),
            serde_json::to_value(proof).expect("proof serialization is infallible"),
        );
    }
    value
}

/// Generic verify over a JSON-LD value — the same three checks as the typed
/// path: (1) the content hash recomputes over `hashing_view`, (2) the signature