In human-computer interaction, self-disclosure of sensitive information regarding distressing experiences requires the establishment of a trust channel between the user and the digital tool. As privacy and security have been identified as factors that contribute to increased levels of trust, they could be utilized to design digital tools that encourage and empower adolescents to disclose school bullying. This work-in-progress paper presents an interdisciplinary research project aimed at combining appropriate levels of usability and security to design a privacy scheme for adolescents in order to provide a digital solution that will help anti-bullying intervention at schools in Switzerland and beyond. The process for designing the interaction and interface of the digital tool is presented in the context of interviews with domain experts. Furthermore, participatory design workshops with Swiss teachers and students are used to inform the key trustful features that the tool should exhibit.