According to the Berlin Group Implementation guidelines, there can be different methods for the PSU to carry out its strong authentication. AION is supporting the following one(s):
Redirect OAuth2 SCA Approach
The PSU is redirected from the TPP interface to a web browser in order to perform her/his SCA.
Redirect App2App SCA Approach based on Universal Links
The PSU is directly redirected from the TPP interface to its installed mobile banking application in order to perform her/his SCA. If the mobile banking application is not installed on the PSUs device, she/he will be redirected to a web browser. The Redirect OAuth2 SCA Approach applies.