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

# Signature

> Base StructureDefinition for Signature Type: A signature along with supporting context. The signature may be a digital signature that is cryptographic in nature, or some other signature acceptable to the domain. This other signature may be as simple as a graphical image representing a hand-written signature, or a signature ceremony Different signature approaches have different utilities.

## Properties

| Name | Required | Type | Description |
| - | - | - | - |
| id | No | string | Unique id for inter-element referencing |
| extension | No | [Extension](/medical-api/fhir/data-types/extension)\[] | Additional content defined by implementations |
| type | Yes | [Coding](/medical-api/fhir/data-types/coding)\[] | Indication of the reason the entity signed the object(s) |
| when | Yes | instant | When the signature was created |
| who | Yes | Reference\<[Practitioner](/medical-api/fhir/resources/practitioner) / [PractitionerRole](/medical-api/fhir/resources/practitionerrole) / [RelatedPerson](/medical-api/fhir/resources/relatedperson) / [Patient](/medical-api/fhir/resources/patient) / [Device](/medical-api/fhir/resources/device) / [Organization](/medical-api/fhir/resources/organization)> | Who signed |
| onBehalfOf | No | Reference\<[Practitioner](/medical-api/fhir/resources/practitioner) / [PractitionerRole](/medical-api/fhir/resources/practitionerrole) / [RelatedPerson](/medical-api/fhir/resources/relatedperson) / [Patient](/medical-api/fhir/resources/patient) / [Device](/medical-api/fhir/resources/device) / [Organization](/medical-api/fhir/resources/organization)> | The party represented |
| targetFormat | No | code | The technical format of the signed resources |
| sigFormat | No | code | The technical format of the signature |
| data | No | base64Binary | The actual signature content (XML DigSig. JWS, picture, etc.) |


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