A user could have many json files (about 40mb per file) containing very private information about them and other people. I want to process these json files on the users device to keep this information private. By processing the data I would only extract statistical data about the contents of the processed json files. This statistical data will be stored on the users machine in a local json file. They could then upload that statistical json file to a website to get a dashboard based on the provided information or just keep the statistical json file for their own use.

My initial thought would be to use something like Flutter to build a desktop app that people could use on their devices (windows, macOS or linux). The Flutter app would process all json files and store the statistical json file on the users local machine.

Could Flutter handle something like this? Is there a better way to do this that I am missing?
Any opinions would help.