Norimatsu, TakashiNakamura, YuichiYamauchi, ToshihiroRoßnagel, HeikoSchunck, Christian H.Mödersheim, Sebastian2022-06-072022-06-072022978-3-88579-719-7https://dl.gi.de/handle/20.500.12116/38707Keycloak is identity and access control open-source software. When used for open banking, where many OAuth 2.0 clients need to be managed and a different OAuth 2.0-based security profile needs to be applied to each type of API, the problem of increasing managerial costs by the Keycloak administrator occurs because Keycloak's security profile logic depends on the client settings, and the logic cannot be changed for each client's request. This paper proposes its solution by separating the security profile logic from the client settings, and by changing the security profile for each client's request based on the content of the request, and actual security profiles Financial-grade API (FAPI) are implemented to Keycloak. The paper calculates managerial costs in both the existing and proposed methods in scenarios managing FAPI, and compares the results. The comparison shows that using the proposed method reduces costs. Our implementations are contributed to Keycloak.enOAuth 2.0Security ProfileFAPIOpen SourceKeycloakOpen BankingText/Conference Paper10.18420/OID2022_071617-5468