# Provenance Integrity

<figure><img src="/files/kM9X9w0ChedofU73GCfZ" alt="" width="563"><figcaption></figcaption></figure>

A business wants to be assured about the data integrity (accuracy and authenticity) of the provenance (or history of events) of their publicly linked company documents. To achieve that, the business wants to easily verify the provenance of a company document.

This use case is an extension of the Data Integrity use case (described [here](/nchain-event/independent-records/tutorials/data-integrity.md)) and is similar to the Collection Integrity use case (described in the previous section). The solution includes these steps for each company document event:

* Next event registration – the company document is kept hidden but registered and linked on the blockchain
* Nth event verification – the company document and links are compared with the blockchain to determine validity

{% hint style="warning" %}
Please be aware that verification always requires the original company document.
{% endhint %}

We will use the Linked Record REST API class wrapper as described in the previous section.

## **Next Event Registration**

Whenever the company document is updated in the application database, this procedure is performed to register a fingerprint of the new company document on the blockchain, and record all provenance:

```typescript
  aRecord = "get the latest company document for the documentId"

  aSalt = time.now()

  oldLocation = either 0 or provenance[count-1].location for the documentId

  newLocation = event.upsert(aRecord, aSalt, oldLocation) // Register a fingerprint

  // persist aRecord, aSalt, newLocation in provenance[count] for the documentId

  // increment and persist count for the documentId

```

## **Nth Event Verification**

At any arbitrary time later, the business can verify the Nth previous version (0 for the latest) of the company document with this procedure:

```typescript
  nthRecord = provenance[count-1-Nth].record for the documentId

  nthSalt = provenance[count-1-Nth].salt for the documentId

  previousLoc = either 0 or collection[count-1-Nth - 1].location for the documentId

  nthLocation = provenance[count-1-Nth].location for the documentId

  nextLoc = either 0 or collection[count-1-Nth] + 1].location for the documentId

  result = event.verify(nthRecord, nthSalt, previousLoc, nthLocation, nextLoc)

  if result = match // nthRecord and links are verified as valid
  if result = mismatch // nthRecord or links are verified as invalid
  if result = error // try again later

```

"nthRecord" must contain identical fields to those that were originally registered to the blockchain.

Handling the different possible responses is described in detail in the Data Integrity use case [here](/nchain-event/independent-records/tutorials/data-integrity.md).&#x20;

The actual syntax is shown in [Verify Link Record](/nchain-event/linked-records/api-workflow/verify-link-record-+.md) below.

The business can employ iteration to verify a range of versions of the company document.

This example ignores issues like the data retention policy of the business.

## Benefits

* Provides high confidence of the validity of verified company documents for the business
* Provides high confidence to auditors/users who verify the original company document of its validity.


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