ACP Client-initiated Backchannel Authentication modes
Get familiar with the Client-initiated Backchannel Authentication (CIBA) modes: Poll and Ping. Learn the differences between modes and get information on how each mode works.
CIBA modes in a nutshell
The OpenID Connect Client-Initiated Backchannel Authentication Flow specification allows client applications to get results of its authentication using two ways:
POLL mode - where a client application sends continuous polling requests to ACP up to the point it receives a response with a success
PING mode - where ACP posts a notification (after the process on the authentication device is finished) to a client notification endpoint configured for this client application.
In the POLL mode, after a client application receives a response from the ACP’s backchannel authentication endpoint, the client repeats multiple token requests (hence the name, polling) to the ACP’s token endpoint.
When a clients waits for the result of the authentication, it repeats token requests. Until the
authentication process is not finished, ACP responds with the
authorization_pending response or with the
slow_down response if there are too many requests
Continuous requests are sent until the client receives a token in the response or the
response contains an error different from
The PING mode differs from the POLL mode, as there are no repeated requests to the token endpoint. Instead, once ACP receives an authentication result from the authentication device, it notifies the client application using the client notification endpoint configured for this application. After the client receives such a notification with a successful authentication result, it may request a token.
The client notification endpoint must be set for a client application during its registration. It must be a HTTPs URL and it must utlize the Transport Layer Security (TLS).
Both in the POLL and in the PING mode a client application receives an access token as a result of a request to the token endpoint. Such a request must contain the following CIBA-specific parameters:
|grant_type||This parameter provides information to ACP which grant type is used. Both for the PING and the POLL modes, the value must be set to
|auth_req_id||Authentication request ID that is issued from the backchannel authentication endpoint.|
In all CIBA modes, the following client authentication methods are allowed:
none client authentication cannot be used in the CIBA grant flow
as only confidential clients are able to use CIBA securely.