Verifying that certain data is encrypted (or at least indistinguishable from random data)

Question
The question is in the title, but here are more details:
I want my server to have an upload endpoint (single POST for small data or multipart for larger data) where clients can upload data.
However:

Clients can upload only encryp… Continue reading Verifying that certain data is encrypted (or at least indistinguishable from random data)