suggestions for secure files exchange/collaboration platform

Hello, I'm taking part of a Hackathon in our organization, me and the the devs are thinking of developing a secure files exchange platform for exchanging/sharing CAD files between multiple projects inside my organisation and outside the organization with our partners. Do you suggest any project or data model I can refer to as a starting point. Also we are thinking to use AWS S3 for storing our files…do you have a recommendation for the tech stack for a project in this size? We are experienced with Angular and Java spring boot/Maven.

Thank you for your comments/advise in advance!