| UUID | uuid | string | | Universally Unique Identifier. |
| Key | key | cbc.Key | | Key used to identify the attachment inside the document. |
| Code | code | cbc.Code | | Code used to identify the payload of the attachment. |
| Name | name | string | true | Filename of the attachment. |
| Description | description | string | | Details of why the attachment is being included and details on what it contains. |
| URL | url | string | | URL of where to find the attachment. Prefer using this field over the Data field. |
| Digest | digest | dsig.Digest | | Digest is used to verify the integrity of the attachment when downloaded from the URL. |
| MIME Type | mime | string | | MIME type of the attachment. |