> For AI agents: [llms.txt](https://docs.trustedauth.com/llms.txt) provides a Markdown index of this documentation.

# Authentication and support

Use this page when you need a quick reference for the Authentication API security scheme or support details.

## Authentication

The Authentication API uses the following security scheme:

| Field                 | Value           |
| --------------------- | --------------- |
| Security scheme type  | `apiKey`        |
| Header parameter name | `Authorization` |

Authentication flow examples show the `Authorization` header in context:

- [One-factor authentication](/api/auth-api/rest-examples/one-factor-authentication.md)
- [Two-factor authentication](/api/auth-api/rest-examples/two-factor-authentication.md)
- [External authentication with a second factor](/api/auth-api/rest-examples/external-plus-second-factor.md)

## Contact

For help with Entrust Identity as a Service Authentication API integrations, contact <support@entrust.com> or visit <https://www.entrust.com/>.