The present disclosure relates to computer-implemented methods, software, and systems for securely generating a new access token based on relatively long-lasting refresh tokens in self-contained format. A first request to generate a new access token for authorization of a client application with an application server is received and includes a first protected version of a refresh token. The first protected version of the refresh token is an encrypted version of the refresh token based on a first client identifier. The first protected version of the refresh token is decrypted to determine content of the refresh token based on a second client identifier of the client application that is externally invoked for validating the authorization. In response to successfully decrypting the first protected version, performing a validation of the refresh token. In response to successfully validating the refresh token, generating the new access token and providing it to the client application.