And if you recall the discussions about PGP and how a government hounded them for being too secure then you know that unless you are willing to be dragged through the courts for over a decade you can't develop such a thing.
This is not the end of the story but the beginning. You should also research the FBI's "Going Dark" program.
Wanna to upload files to the cloud like dropbox, but are they secure?
I'm thinking whether there exist a browser that can encrypt my file whenever I upload documents and decrypt it whenever I download. I believe this is doable but seems none of the browser implemented this.
Can some one "a Professional browser developer" make such a secure browser?