https://github.com/blindnet-io/blindsend
We made it for people to whom clients send sensitive data (doctors, layers, financial advisors) who can use it to send a one-time upload link to their clients, and have blidnsend take care of making the transfer end-to-end encrypted. We hope it will be useful to many who have to deal with GDPR compliance.
You can also call blindsend server from any application/software that you have if you wish to enable your users to exchange files without your system/app having any access to the content, and we are also developing blindsend Java library. As such, we hope blinsend will make implementing end-to-end encrypted file exchange easier, and we are excited to make it open source so that everyone could benefit from it.
I would love to hear your feedback, and if you use blindsend please let me know if I can be of any assistance.
Cheers