HTTP Message Elements {#restgs-http-const-elements}
===================================================

An HTTP message is constructed using HTTP headers and an HTTP message body.

**HTTP Message Headers**
:
Your message header must include these HTTP header fields:

    |  HTTP Header Field  |                                                                                Description                                                                                 |
    |---------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
    | **content-type**    | Also known as the Multipurpose Internet Mail Extension (MIME) type, it is the identifier of the media or file type resource. You can set the value to: `application/json`  |
    | **host**            | The transaction endpoint (`api.cybersource.com`).                                                                                                                          |
    | **v-c-date**        | The date of the transaction in the RFC1123 format. Example: `Thu, 18 Jul 2019 00:18:03 GMT`                                                                                |
    | **v-c-merchant-id** | Your `Cybersource` transacting merchant ID (MID). If you are a portfolio or merchant account user, set this to the transacting merchant ID you send requests on behalf of. |
    | **digest**          | A hash of the HTTP message body that contains your API request. The digest field does not apply to `GET` API requests.                                                     |
    | **signature**       | The digital signature, which is constructed using the values of the other headers and secured by your private key.                                                         |
    [HTTP Header Fields]

**HTTP Message Body**
:
Your API request.