In this paper, we present some results on multimodality implementation resulting from the VINSI (Vérification dIdentité Numérique Sécurisée Itinérante for Secured Mobile Digital Identity Verification) French project. The VINSI handheld terminal allows identity verification in mobile conditions (airport gates) using two biometrics usable in future biometric passports (fingerprint and face). We propose an incremental fusion strategy aiming at improving the global performance of the combined system over each individual recognizer while optimizing the cost resulting from the fusion. Indeed, in this kind of application, time and complexity optimization is essential. To this aim, we split the fingerprint scores range into different interest zones, on which we do not apply the same strategy depending on the relative quality of the modalities at hand. Results on a virtual database corresponding to VINSI applicative conditions (Combination of BIOMET fingerprints and FRGCv2 faces) show that this incremental fusion strategy allows the same improvement in performance as global fusion methods while significantly reducing the cost