Identifying image provenance: An analysis of mobile instant messaging apps

Studying the impact of sharing platforms like social networks and messaging services on multimedia content nowadays represents a due step in multimedia forensics research. In this framework, we study the characteristics of images that are uploaded and shared through three popular mobile messaging apps combined with two different sending mobile operating systems (OS). In our analysis, we consider information contained both in the image signal and in the metadata of the image file. We show that it is generally possible to identify a posteriori the last app and the OS that have been used for uploading. This is done by considering different scenarios involving images shared both once and twice. Moreover, we show that, by leveraging the knowledge of the last sharing app and system, it is possible to retrieve information on the previous sharing step for double shared images. In relation to prior works, a discussion on the influence of the rescaling and recompression mechanism - usually performed differently through apps and OSs - is also proposed, and the feasibility of retrieving the compression parameters of the image before being shared is assessed.