Research in methods for achieving secure voice anonymization : Evaluation and improvement of voice anonymization techniques for whistleblowing

Abstract: Safe whistleblowing within companies could give a more transparent and open society, and keeping the whistleblower safe is key, this has led to a new EU Whistleblowing Directive requiring each organization with more than 249 employees to provide an internal channel for whistleblowing before 17 July 2022. A whistleblowing service within an entity should provide secure communication for the organization and its employees. One way to make whistleblowing more accessible is by providing a service for verbal reporting, for example by recording and sending voice messages. However, ensuring that the speaker is secure and can feel anonymous can be difficult since speech varies between individuals - different accents, pitch, or the speed of the voice are examples of factors that a speaker can be identified by. Common ways of voice anonymization, that you hear on the news for example, can often be backtracked or in other ways be deanonymized such that the speaker’s identity is revealed, especially for people who know the speaker. Today we have many developing technologies, such as machine learning, which could be used to greatly improve anonymity or deanonymization. However, greater anonymity is often costly with regard to the intelligibility and sometimes the naturalness of the voice content. Therefore, we studied and evaluated a number of anonymization methods with respect to anonymity, intelligibility, and overall user-friendliness. The aim of this was to map what anonymization methods are suitable for whistleblowing and implement proof of concepts of such an anonymizer. The results show differences between anonymization methods and that some perform better than others, but in different ways. Different methods should be selected depending on the perceived threat. We designed working proof of concepts that can be used in a whistleblowing service and present when respective solutions could be used. Our work shows ways for securer whistleblowing and will be a basis for future work and implementation for the host company Nebulr.