Abstract: Digital fingerprinting is an emerging forensic tool to protect coypright contents from illegal alteration and unauthorized redistribution. It uses traditional data-hiding techniques to seamlessly embed a unique label, known as ``fingerprint'', into each distributed copy to track the usage of multimedia or generic data. Recently, fingerprinting is also used in communication systems to identify the transmitting user. Collusion attack is a cost-effective attack against multimedia fingerprinting. The attackers collectively mount collusion using all their copies to reduce the energy of the embedded fingerprints. In this talk, we will first present our work on low-complexity binary anti-collusion fingerprint design which performs the same as the state-of-the-art Tardos fingerprint but with much lower computational complexity. Although binary fingerprinting has its advantage in practical systems, Gaussian fingerprinting is much more collusion-resistant. We will then introduce how fingerprint detector can improve its performance by utilizing the side information of collusion with Gaussian fingerprint. Furthermore, fingerprinting can also be used for improving physical-layer security in wireless communications. When applied to wireless transmissions, robust physical layer fingerprints can enable signal authentication even when the signal itself is unrecoverable due to low signal to noise ratio or fading conditions. We present a physical-layer fingerprint-embedding scheme for orthogonal frequency division multiplexing transmissions, where the fingerprint signal conveys a low capacity communication suitable for authenticating the transmission and further facilitating secure communications.