A watermark-based dynamic ad insertion (DAI) technique for presenting different users of content different advertisements based on the user's profile for content viewed on broadcast channels or in multichannel video programming distributor (MVPD) channels. A number of solutions issues with watermark-based DAI are presented. Interoperability is addressed by providing a multiplexing technique so that the DAI watermarks do not interfere with other watermarks, such as ATSC 3.0 watermarks. Reliability is addressed by providing a matched filtering technique. Security is addressed by providing a mutual authentication technique.