Digital Object Hashing

This is an experimental feature.

Cordra has a feature that when enabled automatically generates hashes of an object and its components on the server when an object is created or modified.

Hash generation is configured on a per type basis. To enable hashing for a particular type set the hashObject property on the schema object to true.

The generated hashes are stored as a JSON object within the object’s metadata property. Each hash is a hex-encoded string of the bytes using SHA-256.

{
    "hashes": {
      "alg": "SHA-256",
      "content": "c39e84af6b49c3c6dee72b3d6fa912216f12b8ddb1507f2283ea4a1f5e2f751d",
      "payloads": {
        "payloadName": "c5601d266987ac885ca96522b1b4e439feb7eca39f0fe1111f7342b63b6468f3"
      },
      "full": "8a3251e1a133c65630d0566856f0049b3feb82d0bebc5de58b513c09ccb109ad"
    }
}

The content hash is a hash of the JSON content of the object. The JSON is first canonicalized, ensuring consistent property ordering and value formats.

The bytes of each payload are individually hashed and stored in the payloads section of the hashes object.

If the object contains userMetadata, the hashes JSON object will contain an additional hash for that component.

The full hash is a hash over the full Cordra object including the hashes of any payloads.

It is possible to verify the hashes in server-side JavaScript, such as in lifecycle hooks or Type methods, as follows:

const cordraUtil = require('cordra-util');

const verificationReport = cordraUtil.verifyHashes(cordraObject);