In this paper, we propose a new watermarking reinforcement approach that ensures a suitable compromise between the security level of a person's biometric data and the computational complexity of the proposed scheme while maintaining a reduced storage space and a good visual quality of the watermarked host image. We validate the suggested approach on two biometric modalities, fingerprint and face, which are among the most frequently deployed and mature ones in biometric watermarking systems. The improved level of safety is ensured by a combined watermarking scheme. In fact, the same watermarking algorithm is applied twice in succession. First, the face of an individual is watermarked by the local characteristics, minutia, of his/her fingerprint. Second, the previously watermarked face image is inserted into the original image of the fingerprint as supplementary identity information. Beside securing the biometric data, the exploration of the watermarked image has shown interesting performances in individuals' verification. The results of various tests performed on the Biosecure multimodal database have demonstrated that the proposed method is robust to several signal processing attacks