The EBA notes that “there would appear to currently be three main ways or methods of carrying out the authentication procedure of the PSU through a dedicated interface, and APIs in particular, namely redirection, embedded approaches and decoupled approaches (or a combination thereof). In the cases of redirection and decoupled approaches, PSU’s authentication data is exchanged directly between PSUs and ASPSPs, as opposed to embedded approaches, in which PSU’s authentication data is exchanged between TPPs and ASPSPs through the interface.”

PSD2 requires strong customer authentication to be performed in certain circumstances. The RTS requires that this application of strong customer authorisation is based on the use of elements, which are categorised as knowledge (something only the user knows), possession (something only the user possesses) and inherence (something the user is). These elements require adequate security features, which include ensuring that they are applied independently, so that the breach of any element does not compromise the reliability off the other.

ASPSPs implementing redirection should note that the FCA Approach document  (Payment Services Regulations 2017 and the Electronic Money Regulations 2011) states it is not aware of any reason for ASPSPs to request strong customer authentication more than once when facilitating authentication for a single session of access to account information or a single payment initiation.

The Open Banking 2.0 standards specified redirection authentication flows only and the current ASPSP implementations of redirection are predominantly browser-based, whereby the PSU is redirected from the TPP app or website to the ASPSP’s website in order to authenticate. It is essential that when redirection is implemented it also allows for the PSU to use their ASPSP mobile app to authenticate, if the PSU uses this method of authentication when accessing their ASPSP’s channel directly.

Redirection has a specific TPP channel and device dependency and therefore cannot support channel agnostic use cases that involve telephony, POS, and IoT devices, or where physical PSU interaction is either not possible or not required within the TPP channel. These use cases can be supported using a decoupled approach to authentication.

Redirection based authentication has a range of possible experiences for a PSU based on whether the PSU has an ASPSP app or not, and the device on which the PSU is consuming the TPP (AISP/PISP/CBPII) service.

The FCA have made clear in their Approach document that PSUs must be able to authenticate using the authentication methods they are accustomed to using  via the banking application (‘app’) on a mobile phone if accessing accounts via a TPP.

We have used one example of an AISP and PISP journey to demonstrate how redirection flows must work. These apply to variations in AIS/PIS/CBPII journeys related to the order of application of SCA and are covered in sections 5, 6 and 7.

A major addition to the Open Banking standards known as “Decoupled” authentication, where typically the PSU uses a separate secondary device to authenticate with the ASPSP. This model allows for a number of innovative solutions and has the added benefit of allowing a PSU to use their mobile phone to authenticate. Taking advantage of biometrics for SCA, where they are engaging with a PISP through a separate terminal, such as a point of sale (POS) device.

We have used examples for a PIS journey, but the same principles apply for AIS and CBPII journeys.

Under the Decoupled standard, the following customer experiences are available

SCA -RTS includes a number of exemptions from the application of strong customer  authentication, which include payments made to trusted beneficiaries, low value payments and payment based on transaction risk analysis. The application or not of SCA and the exact implementation of an SCA exemption is at the ASPSP’s discretion.

This section highlights the OB API Standard capabilities to allow PISPs to provide sufficient information about a transaction and about the PSU (if available) to enable the ASPSP to determine whether or not the exemptions are applicable.