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# Authenticate with AWS Signature authentication workflow in Postman

AWS Signature is the authorization workflow for Amazon Web Services requests. AWS uses a custom HTTP scheme based on a keyed-HMAC (Hash Message Authentication Code) for authentication.

The official AWS Signature documentation provides more detail:

* [Signing and Authenticating REST Requests](https://docs.aws.amazon.com/AmazonS3/latest/userguide/RESTAuthentication.html)
* [Invoke REST APIs in API Gateway](https://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-call-api.html)

To use AWS Signature, do the following:

1. In the **Authorization** tab for a request, select **AWS Signature** from the **Auth Type** dropdown list.

2. Select the location where Postman will append your AWS auth details using the **Add authorization data to** dropdown list. Select **Request Headers** or **Request URL**.

   * If you select **Request Headers**, Postman adds `Authorization` and `X-Amz-` prefixed fields in the **Headers** tab.
   * If you select **Request URL**, Postman adds the auth details in **Params** with keys prefixed `X-Amz-`.

3. Enter your **AccessKey** and **SecretKey** values. For extra security, use your [Postman Vault](/docs/use/postman-vault/postman-vault-secrets/) to store sensitive data as vault secrets.

4. You can optionally set advanced fields in the **Advanced configuration** section, but Postman generates these automatically if necessary.

The AWS Signature parameters are as follows:

* **AWS Region** - The region receiving the request (defaults to `us-east-1`).
* **Service Name** - The service receiving the request.
* **Session Token** - Required only when using temporary security credentials.