The near future world signs everything with a personal identifier so they can prove they what people are seeing is genuine.
I imagine these identifiers could be extended to things like security cameras and things too so that there could be some verification that the video footage hasn't been doctored.
All of this of course relies on the general public getting the knowledge and tools to seamlessly do this verification on a daily basis. In the book it's mostly taken care of using google glass style wearables.