> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pipevest.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Content Digest

The [content digest signature](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Digest) that is used to validate the HTTP message content. A hashing algorithm is used to create a digest of the message body.
With the algorithm you can then rehash the message body and validate it against the pre-computed content-digest.

<Note>
  The content digest should only be computed for requests where message body is
  present
</Note>

#### Generate Content Digest

Although `sha-256` generated digests are considered secure, we recommend using `sha-512`.

<img className="block dark:hidden" height="200" src="https://mintcdn.com/pipevest/l6kPGYU9W55pgekc/images/hash-content-digest.png?fit=max&auto=format&n=l6kPGYU9W55pgekc&q=85&s=c6d1fc1f895d839fa2b7485a71f6a87b" data-path="images/hash-content-digest.png" />

<img className="hidden dark:block" height="200" src="https://mintcdn.com/pipevest/l6kPGYU9W55pgekc/images/hash-content-digest-dark.png?fit=max&auto=format&n=l6kPGYU9W55pgekc&q=85&s=7578ddef85edb978950eff0e56c61ca0" data-path="images/hash-content-digest-dark.png" />

<Steps>
  <Step title="Compute Content Digest">
    <Tabs>
      <Tab title="Javascript">
        ```javascript theme={null}
          import crypto from "crypto";

          // Define the algorithm
          let algorithm = "sha512";

          // Define the message
          let message = JSON.stringify({
            firstName: "John",
            ...
          });

          // Create the digest in base64 encoding
          const digestBase64 = crypto.createHash(algorithm).update(message).digest("base64");

          // Create content digest string
          const contentDigest = `sha-512=:${digestBase64}:`;
        ```
      </Tab>

      <Tab title="Python">
        ```python theme={null}
          import hashlib
          import json

          # Define the message
          message = json.dumps({
            "firstName": "John",
            ...
          })

          # Create the sha512 Digest
          digest_sha = hashlib.sha512()

          # Update the message
          digest_sha.update(message)

          # Base64 encode digest
          digest_base64 = base64.b64encode(digest_sha)

          # Create content digest string
          content_digest = f'sha-512:{digest_base64}:'
        ```
      </Tab>
    </Tabs>
  </Step>

  <Step title="Make Signed Request">
    In the below example request:

    * `sha-512`: The algorithm used to hash the content message
    * `RK/0...abDg=`: Base64 representation resulting from the hashed content message

    ```bash theme={null}
      curl --request POST \
        --url https://api.pipevest.com/v1/customers?sort=ASC \
        --header 'Content-Type: application/json' \
        --header 'Content-Digest: sha-512=:RK/0qy18MlBSVnWgjwz6lZEWjP/lF5HF9bvEF8FabDg=:' \
        --header 'Content-Length: 18' \
        --header 'Authorization: Bearer 123456' \
        --header 'X-Client-Id: 123456' \
        --header 'X-Idempotency-Key: 123456' \
        ...
        --data '{"firstName": "John", "lastName": "Doe"}'
    ```
  </Step>
</Steps>

#### Verify Content Digest

<img className="block dark:hidden" height="100" src="https://mintcdn.com/pipevest/l6kPGYU9W55pgekc/images/verify-content-digest.png?fit=max&auto=format&n=l6kPGYU9W55pgekc&q=85&s=a6c85fe04d3a7c773bb1515e5e8ba052" data-path="images/verify-content-digest.png" />

<img className="hidden dark:block" height="200" src="https://mintcdn.com/pipevest/l6kPGYU9W55pgekc/images/verify-content-digest-dark.png?fit=max&auto=format&n=l6kPGYU9W55pgekc&q=85&s=58d1b32adb31ba960bc13c6c1976b5e8" data-path="images/verify-content-digest-dark.png" />

<Steps>
  <Step title="Re-compute Content Digest">
    See `Step 1` in [Generate Content Digest](/concepts/http-signature/content-digest#generate-content-digest)

    <Note>
      We will call this `computed-content-digest`.
    </Note>
  </Step>

  <Step title="Compare Digests">
    Compare `computed-content-digest` to the one that was passed along in the original http header (i.e. - `header-content-digest`).

    ```
    computed-content-digest === header-content-digest
    ```

    <Tip>In the example below, the `header-content-digest` equals `RK/08...FabDg=`</Tip>

    ```bash theme={null}
      curl --request POST \
        --url https://api.pipevest.com/v1/customers \
        --header 'Content-Digest: sha-512=:RK/08...FabDg=:' \
        ....
    ```
  </Step>

  <Step title="Verify or Reject">
    Reject the message, if `computed-content-digest` does not equal `header-content-digest`.
  </Step>
</Steps>